Global Warming and Chaos Theory

[McHeathen]

There has been much controversy concerning Global Warming: sun spot activity, only heat radiation at 15 microns being trapped by CO2, vast amounts of greenhouse gases going intot he atmosphere from exploding volcanos and the general cyclical nature of climate change have attempted to explain the insignificance on human interaction on the environment as having a significant effect on GM.

I came across documentary which made reference to how 'Chaos Theory' explained the significant effect of human interaction on climate change. Can someone give some elaboration on this?

[Bored Wombat]

There has been much controversy concerning Global Warming: sun spot activity, only heat radiation at 15 microns being trapped by CO2, vast amounts of greenhouse gases going into the atmosphere from exploding volcanoes and the general cyclical nature of climate change have attempted to explain the insignificance on human interaction on the environment as having a significant effect on GM.

I came across documentary which made reference to how 'Chaos Theory' explained the significant effect of human interaction on climate change. Can someone give some elaboration on this?

I don't think that there has been much controversy concerning global warming from within the scientific community.

Sunspot activity does affect the climate but variations in solar irradiance are probably less than 10% of the change in radiative forcing due to the anthropogenic part of the greenhouse effect.

There are a few absorption bands of CO2 that make it a greenhouse gas.

Volcanoes produce a very small fraction of the CO2 compared to anthropogenic sources.

The since the middle of last century this warming is mostly (or entirely) anthropogenic. It is not cyclic.


However, I imagine that chaos theory wrt climate change is because the climate system exhibits sensitive dependence on initial condition. This means that if someone in Australia paints their house roof dark green, then the thermal eddies created there can have a significant effect on the Atlantic Hurricanes two years later. Impossible to predict, and although it probably is a change in climate, it is not really "climate change" by which is generally meant the effect on climate of anthropogenic global warming and its effects.

[Andre]

I don't think that there has been much controversy concerning global warming from within the scientific community.

And I don't think that this is a very accurate representation of the reality. For instance the Assessment Reports of the IPCC have not been peer reviewed in the classical way, because the editors were free to accept or reject comments from the reviewers. The summaries for policy makers was not reviewed by the specialists but only by government representatives and showed a somewhat different picture than the chapters.

Therefore the specialists decided to write their own Independent Summary for Policy Makers, which was reviewed by peers:

http://www.uoguelph.ca/~rmckitri/research/ispm.html

Having somewhat different conclusions (http://www.uoguelph.ca/~rmckitri/research/ISPM.pdf) than the general party lines:

The Earth’s climate is an extremely complex system and we must not understate the difficulties involved in analyzing it. Despite the many data limitations and uncertainties, knowledge of the climate system continues to advance based on improved and expanding data sets and improved understanding of meteorological and oceanographic mechanisms.

The climate in most places has undergone minor changes over the past 200 years, and the land-based surface temperature record of the past 100 years exhibits warming trends in many places. Measurement problems, including uneven sampling, missing data and local land-use changes, make interpretation of these trends difficult. Other, more stable data sets, such as satellite, radiosonde and ocean temperatures yield smaller warming trends. The actual climate change in many locations has been relatively small and within the range of known natural variability. There is no compelling evidence that dangerous or unprecedented changes are underway.

The available data over the past century can be interpreted within the framework of a variety of hypotheses as to cause and mechanisms for the measured changes. The hypothesis that greenhouse gas emissions have produced or are capable of producing a significant warming of the Earth’s climate since the start of the industrial era is credible, and merits continued attention. However, the hypothesis cannot be proven by formal theoretical arguments, and the available data allow the hypothesis to be credibly disputed.

Arguments for the hypothesis rely on computer simulations, which can never be decisive as supporting evidence. The computer models in use are not, by necessity, direct calculations of all basic physics but rely upon empirical approximations for many of the smaller scale processes of the oceans and atmosphere. They are tuned to produce a credible simulation of current global climate statistics, but this does not guarantee reliability in future climate regimes. And there are enough degrees of freedom in tunable models that simulations cannot serve as supporting evidence for any one tuning scheme, such as that associated with a strong effect from greenhouse gases.

There is no evidence provided by the IPCC in its Fourth Assessment Report that the uncertainty can be formally resolved from first principles, statistical hypothesis testing or modeling exercises. Consequently, there will remain an unavoidable element of uncertainty as to the extent that humans are contributing to future climate change, and indeed whether or not such change is a good or bad thing.

[Bored Wombat]

And I don't think that this is a very accurate representation of the reality.
On the other hand, in the scientific literature there is very little denialism.

The American Meteorological Society (6), the American Geophysical Union (7), and the American Association for the Advancement of Science (AAAS) all have issued statements in recent years concluding that the evidence for human modification of climate is compelling (8).

The drafting of such reports and statements involves many opportunities for comment, criticism, and revision, and it is not likely that they would diverge greatly from the opinions of the societies' members. Nevertheless, they might downplay legitimate dissenting opinions. That hypothesis was tested by analyzing 928 abstracts, published in refereed scientific journals between 1993 and 2003, and listed in the ISI database with the keywords "climate change" (9).

The 928 papers were divided into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. Of all the papers, 75% fell into the first three categories, either explicitly or implicitly accepting the consensus view; 25% dealt with methods or paleoclimate, taking no position on current anthropogenic climate change. Remarkably, none of the papers disagreed with the consensus position. (Beyond the Ivory Tower (http://www.sciencemag.org/cgi/content/full/306/5702/1686), Oreskes, Science (2004)

Actually there has been a comprehensive list of scientific societies of international standing, including the Joint Science Academies of Australia, Belgium, Brazil, Canada, the Caribbean, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, Mexico, New Zealand, Sweden, and the United Kingdom.

Plus:
International Council of Academies of Engineering and Technological Sciences
European Academy of Sciences and Arts
Network of African Science Academies
National Research Council (US)
European Science Foundation
American Association for the Advancement of Science
Federation of American Scientists
World Meteorological Organization
American Meteorological Society
Royal Meteorological Society (UK)
Australian Meteorological and Oceanographic Society
Canadian Meteorological and Oceanographic Society
Canadian Foundation for Climate and Atmospheric Sciences
International Union for Quaternary Research
American Quaternary Association
Stratigraphy Commission of the Geological Society of London
International Union of Geodesy and Geophysics
International Union of Geological Sciences
European Geosciences Union
Canadian Federation of Earth Sciences
Geological Society of America
American Geophysical Union
American Astronomical Society
American Institute of Physics
American Physical Society
American Chemical Society
Engineers Australia (The Institution of Engineers Australia)
Federal Climate Change Science Program (US)
American Statistical Association

And as with the published papers:

With the July 2007 release of the revised statement by the American Association of Petroleum Geologists, no remaining scientific body of national or international standing is known to reject the basic findings of human influence on recent climate.

(from wiki (http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change#Statements_by _dissenting_organizations))

For instance the Assessment Reports of the IPCC have not been peer reviewed in the classical way, because the editors were free to accept or reject comments from the reviewers.
That's been true of the last two assessment reports ... a concession made to time.
The first two the wording was slogged out at open meetings, with S Fred Singer standing up in the public gallery at every sentence and giving a long speech that everyone there knew was rubbish. (Presumably including himself).


The summaries for policy makers was not reviewed by the specialists but only by government representatives...
That's not quite true. The second draft is the one that the government representatives get to review. By that time is has already been reviewed reasonably exhaustively by specialists.

...and showed a somewhat different picture than the chapters.

However that is true. Government delegations always attempt to water down the danger, and the necessity for action. The most vociferous government delegations at the IPCC have traditionally been USA, China, Saudi Arabia and Kuwait. The worlds biggest consumer of fossil fuels per capita, the world's biggest consumer of fossil fuels, the world's biggest exporter of fossil fuels, and another economy dependent fully on the export of fossil fuels.

And so there is a valid criticism of the IPCC that the reports are too weak. And it is true that anything that is not very clearly true, and with all the research coming down with similar findings, are generally left out at the political review stage. Or not included because of the awareness that they will be chucked by the political review.

But as long as the are read with the understanding that they describe a best case scenario, the IPCC reports are informative to the intended audience ... laymen and politicians. Experts already know from the published research what is going on, and that there is little doubt.

Therefore the specialists decided to write their own Independent Summary for Policy Makers, which was reviewed by peers:

http://www.uoguelph.ca/~rmckitri/research/ispm.html

Ross McKitrick is an economist with known contrarian views on Global Warming, and a particularly enduring bee in his bonnet about northern hemisphere temperature reconstructions.

If he and nine of hid cronies wrote a document to challenge the one written by the IPCC's hundreds of authors and thousands of reviewers, I am not surprised that it has received less attention than the IPCC's one.

[LURCH]

In Chaos Therory, the Butterfly Effect states that very small intputs to a system can have disproportionately large effects. This is a way of trying to explain how the tiny influence of man can change the enitre atmosphere of Earth.

BTW; most of the surveys I've seen show the scientific community split about 60/40.

[Bored Wombat]

BTW; most of the surveys I've seen show the scientific community split about 60/40.

The denialist community are pretty effective at stacking surveys, especially after the damage to their credibility that the Oreskes literature review made plain.

If the split is over whether the current warming is likely to be mostly anthropogenic, and the scientific community is the climate science community, if the split is not about 99.9/0.1, then there's a selection bias, or a crap survey bias.

Because that's about the proportions of the published work.

And there's no disagreement from scientific organisations of any standing.

[Evo]

\And there's no disagreement from scientific organisations of any standing.

WRONG.

I suggest you read the EPA's official stance on Climate Change.

The official US EPA stance on what "is likely" is In short, a growing number of scientific analyses indicate, but cannot prove, that rising levels of greenhouse gases in the atmosphere are contributing to climate change (as theory predicts).

http://www.epa.gov/climatechange/science/stateofknowledge.html

Also, I hope that you are aware that the IPCC hid the first part of their "report" from the public. The final report was not a consensus and they blocked any scientist that questioned what they were doing or provided evidence to the contrary.

IPCC Fourth Assessment Report Papers: Working Group I, The Physical Science Basis of Climate Change, 2005-2007; Expert Review Comments on First-Order Draft, Chapter 1. ESPP IPCCAR4WG1, which was previously withheld from the public until they were sued for the information under the "Freedom of Information Act".

The previously withheld report can be viewed here - http://pds.lib.harvard.edu/pds/view/7794905?n=2&imagesize=1200&jp2Res=.25 Where you can see how the IPCC "picked" the data they wished to present.

If you want to read some good posts on Climate Change, I suggest you search on Vanesch's posts and read them and you can respond to them here. If you don't, I will be glad to post them all here for you.

[vanesch]

The denialist community are pretty effective at stacking surveys, especially after the damage to their credibility that the Oreskes literature review made plain.


There are two kinds of "denialists": there are those who think that they can prove that there is no AGW, and then there are those that think that the scientific certainty displayed about AGW is exaggerated as of now. I belong to the second category, because I adhere to Feynman's statement concerning scientific research (paraphrased quote): "If you don't do everything which is in your power to prove yourself wrong, if you don't take every idea that could show you wrong seriously, then you are fooling yourself in science".

Well, if it does "damage to your credibility" to try to point out some weak points in the argument (and believe me, there are several of them!), then you are infringing on Feynman's statement.

Now, I know that the typical answer to that one is: yes, but someone who questions, say, relativity, or Newtonian mechanics, that's a crackpot, no ? Or someone questioning evolution, that's a religious fool, no ? That is because theories like relativity or Newtonian mechanics or evolution have a huge amount of unquestionable data behind them. You can take down tens or hundreds of those, and you still have solid proof, gathered over time. This is simply not (yet) true for the scientific case of AGW. There are elements, true. Each of those elements has however, some weakness to it. It is not overwhelming. It takes time to turn a speculative theory in a scientific certainty, and during this time, one should adhere to Feynman's advice.
The "solid AGW proof" of a few years ago turned out to have to be modified in such a way that it lost its convincing power (say, hockeystick, say, temperature/CO2 delay in paleodata,...). Refusing to take Feynman's advice, refusing to consider seriously the questioning of the solidity of the proof (you say it yourself, 99,9% of publications are not critical towards the AGW theory) at this point, is falling into the trap Feynman is pointing out, and is btw a sociological phenomenon known as groupthink. It happened in other domains (say, string theory :-).

Of course, nature doesn't care about how people do their science. AGW could well be there. I'm only pointing out that the scientific attitude towards it isn't healthy. One has the idea that one is "scientific" if one endorses the credo, and that one "damages one's credibility" if one asks critical questions. Once this happens, one has left the domain of scientific inquiry, and one is entering the domain of "building a case". I really wonder whether most climate scientists pushing AGW are "trying to prove themselves wrong" or are rather trying to "prove AGW".


And there's no disagreement from scientific organisations of any standing.

That's exactly what Feynman warned about.

[Bored Wombat]

WRONG.

I suggest you read the EPA's official stance on Climate Change.

The official US EPA stance on what "is likely" is

http://www.epa.gov/climatechange/science/stateofknowledge.html

No, that's exactly what I was saying, only a bit stronger.

They say that it is very likely that "Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations".

I know that it is not certain that most of the warming is anthropogenic, but they the EPA does say that it is certain that CO2 is a greenhouse gas, and that it's concentrations have been increased by human activity.

The only question that remains is what is the climate sensitivity to a rise in CO2 from 280ppm to 385ppm?

Well to a doubling it is about 3°C, so it's about 1.4°C for that rise. It may be a lot less, but there is a greater chance that it is a lot more. (If you look at the posterior probability density function for climate sensitivity from this paper: Robust Bayesian Uncertainty Analysis of Climate System Properties Using Markov Chain Monte Carlo Methods (http://www.climate.unibe.ch/~stocker/papers/tomassini07jc1.pdf))

I think even outside minimal estimates of climates sensitivity are 1.5°C per doubling, which is still 0.7°C, which is still most of the warming, but it may not yet be all manifest, so possibly half of the warming is natural. We are talking not very likely though.

Also, I hope that you are aware that the IPCC hid the first part of their "report" from the public. The final report was not a consensus and they blocked any scientist that questioned what they were doing or provided evidence to the contrary.

IPCC Fourth Assessment Report Papers: Working Group I, The Physical Science Basis of Climate Change, 2005-2007; Expert Review Comments on First-Order Draft, Chapter 1. ESPP IPCCAR4WG1, which was previously withheld from the public until they were sued for the information under the "Freedom of Information Act".

The previously withheld report can be viewed here - http://pds.lib.harvard.edu/pds/view/7794905?n=2&imagesize=1200&jp2Res=.25 Where you can see how the IPCC "picked" the data they wished to present.

If you want to read some good posts on Climate Change, I suggest you search on Vanesch's posts and read them and you can respond to them here. If you don't, I will be glad to post them all here for you.

A perusal of the first few pages of comments and responses didn't indicate a bias to me. Did it to you?

It looks as though the IPCC position could have been much stronger, but for space constraints. The first comment in particular, that it should be included that we are returning the CO2 levels to ones that occurred when there was no ice sheet on Antarctica would have been pretty hard hitting in some quarters.

[Bored Wombat]

I belong to the second category, because I adhere to Feynman's statement concerning scientific research (paraphrased quote): "If you don't do everything which is in your power to prove yourself wrong, if you don't take every idea that could show you wrong seriously, then you are fooling yourself in science".

There are a lot more than one climatologist in the world. Even if there are a few who you claim are "fooling themselves in science", then there are plenty who would happliy take a Nobel prise by showing that the greenhouse effect doesn't actually work or that the warming that is temporally and spatially distributed in a way that is highly suggestive of the greenhouse effect, is from some other source.

Well, if it does "damage to your credibility" to try to point out some weak points in the argument (and believe me, there are several of them!), then you are infringing on Feynman's statement.

The "solid AGW proof" of a few years ago turned out to have to be modified in such a way that it lost its convincing power (say, hockeystick, say, temperature/CO2 delay in paleodata,...).
The impression one gets from the IPCC reports is that the case for AGW is in fact much stronger than it was in the late 90s.

And your two examples make me wonder what you've been reading. Not peer reviewed scholarly research, I suspect.

There have been a dozen northern hemisphere temperature reconstructions since Mann et al. 1998. And they are all "hockey sticks":
http://www.realclimate.org/images/ipcc_6_1_large.jpg (from figure 6.10 of the IPCC 2007 working group I report).

The temperature/CO2 delay in paleodata is not at all problematic for AGW. It is known that the ice ages are regular, so they had to be set off by Malankovic cycles, or at least something regular. That an ice age gives way rapidly to a interglacial shows that CO2 is positively feeding back into the global temperature.

In fact careful analysis of paleoclimatic reconstructions of temperature and CO2 concentrations lead to historical climate sensitivity estimates to a doubling of CO2 not unlike current estimates. (which shows how much the behaviour is in line with expectations). Here are four examples of such papers off the top of my head; I'm sure a full literature review would confirm that paeloclimatic reconstructions are not problematic to AGW.

1) Efficiently Constraining Climate Sensitivity with Ensembles
of Paleoclimate Simulations (http://www.jamstec.go.jp/frcgc/research/d3/jules/SOLA.pdf) Annan et al. SOLA (2005)
We attempt to validate the resulting
ensembles against out-of-sample data by comparing
their hindcasts of the Last Glacial Maximum (LGM) to
paleoclimate proxy data, and demonstrate through this
that our ensembles of simulations are probably biased
towards too high a sensitivity. Within the framework of
our single-model ensemble experiment, we show that
climate sensitivity of much greater than 6°C is hard to
reconcile with the paleoclimate record, and that of
greater than 8°C seems virtually impossible. Our
estimate for the most likely climate sensitivity is in the
region of 4.5°C.

2) Climate sensitivity estimated from ensemble simulations of glacial climate (http://www.pik-potsdam.de/~stefan/Publications/Journals/Schneider_etal_ClimDyn_2006.pdf) Schneider von Deimling et al. Climate Dynamics (2006)
Based on our inferred close
relationship between past and future temperature evolution,
our study suggests that paleo-climatic data can
help to reduce uncertainty in future climate projections.
Our inferred uncertainty range for climate sensitivity,
constrained by paleo-data, is 1.2–4.3°C and thus almost
identical to the IPCC estimate.

3) Climate sensitivity constrained by temperature reconstructions over the past seven centuries (http://www.usclivar.org/Pubs/Hegerl042006.pdf) Hegerl et al. Nature (2006)
Here we demonstrate that such
observational estimates of climate sensitivity can be tightened if
reconstructions of Northern Hemisphere temperature over the
past several centuries are considered. We use large-ensemble
energy balance modelling and simulate the temperature
response to past solar, volcanic and greenhouse gas forcing to
determine which climate sensitivities yield simulations that are
in agreement with proxy reconstructions. After accounting for
the uncertainty in reconstructions and estimates of past external
forcing, we find an independent estimate of climate sensitivity
that is very similar to those from instrumental data. If the latter
are combined with the result from all proxy reconstructions,
then the 5–95 per cent range shrinks to 1.5–6.2 K, thus substantially
reducing the probability of very high climate
sensitivity.

4) Climate sensitivity constrained by CO2 concentrations over the past 420 million years (https://wesfiles.wesleyan.edu/home/droyer/web/climate_sensitivity.pdf) Royer et al. Nature (2007)
We conclude that a climate sensitivity greater than
1.5 6C has probably been a robust feature of the Earth’s climate
system over the past 420 million years, regardless of temporal
scaling.

I'm only pointing out that the scientific attitude towards it isn't healthy. One has the idea that one is "scientific" if one endorses the credo, and that one "damages one's credibility" if one asks critical questions.
I don't see that that is happening. Investigations into climate sensitivity are common, follow a wide range to methods, and estimates way outside the accepted range have been published in high profile journals.

The fact that CO2 is a greenhouse gas and that human activity has increased its concentration are not questioned, but there are known.

[vanesch]

There have been a dozen northern hemisphere temperature reconstructions since Mann et al. 1998. And they are all "hockey sticks":
http://www.realclimate.org/images/ipcc_6_1_large.jpg (from figure 6.10 of the IPCC 2007 working group I report).



Let us concentrate exactly (we're using indeed the same data :-) on this "hockey stick".

Compare it to the initial hockey stick on p 3 of
http://www.ipcc.ch/pdf/climate-changes-2001/scientific-basis/scientific-spm-en.pdf

the summary for policy makers in 2001.

Now, admit that there is a world of difference in the convincing power that we are *on an exceptional and dramatic temperature rise* which was the aim of that plot (with well-choosen coloring too) in the last century - a rise that was OBVIOUSLY an order of magnitude larger than what had happened in the last 1000 year.

When you look at the data of the proxies in the 2007 plot, no such *obvious* dramatic rise is present. Nor the values, nor the rise is an order of magnitude above what "seems normal". If this plot had been there in the 2001 report, it wouldn't have alarmed many people. I know that there has been a statistical analysis (you use "torturing the data until they confess" if the data aren't obviously indicating what you want - I know this, I do this sometimes too) that shows that the null hypothesis "the rise in the last 100 years is not greater than any rise in the previous 1000 years" can be rejected with a limited confidence, but admit that it is far from being as dramatic and obvious as it was in the "proof beyond doubt" in the 2001 report.
There is another error in the presentation of the 2007 plot. That is the visual confusion (using well-chosen coloring) of the proxy data and the actual measurements. Clearly, the proxy data are not 100% the same as the actual measurements (the solid black curve doesn't coincide perfectly with the proxies). That means that there is a dynamical system in between both, which can be for instance, a low pass filter. Well, you shouldn't compare data with different dynamical properties if the aim is to show a difference in dynamics (rise in this case). You shouldn't compare actual measurements which show a quick rise, with proxies which don't show such a quick rise, not now, and probably not in the past. Because if those proxies temper quick rise NOW, (low pass filtering), then they might have done so too in the past. So you cannot conclude then that the rise is faster now than back then.

Even better: shift the instrument data and the smooth grey curve back about 1000 years. You'd find about equal agreement. Was there an accute climate catastrophy around the year 1000 ?

Now, tell me, where is this critical analysis present in the current report ?

Leave away the current data (which are not the same as the proxies), and show only the proxies. Do you think that this still has the "hockey stick" conviction power ? You only see a smooth rising before 1000 AD, then a dip and indeed a slightly stronger rise in the last century. NOTHING TO DO with the dramatic effect displayed in the 2001 report. Where is the scientific honesty here ?

[Andre]

Let us concentrate exactly (we're using indeed the same data :-) on this "hockey stick".

Important is the observation that the blade of these hockeystick is glued upon it and that the proxies are not following which basically already refutes the robustness of these proxies.

But there is more, Mann et al 2008 (http://www.pnas.org/content/early/2008/09/02/0805721105.full.pdf) admit that the adbundantly used and recycled tree ring proxies are basically flawed by showing the difference in skill in fig 2:

See also here the glued on blade, not following the proxies (still containing tree rings) and hence refuting the same.

http://gallery.myff.org/gallery/331289/M-2008-3.PNG

See also that the CRU temperatures is a distinct outlier, temperatures were not al all through the roof at the end of the former century; on the contrary.

This is what it should have looked like:

http://gallery.myff.org/gallery/331302/M-2008-4.PNG

So indeed one might challenge scientific honesty.

[vanesch]

The fact that CO2 is a greenhouse gas and that human activity has increased its concentration are not questioned, but there are known.

Well, again, there is no tight proof (although there is suggestive evidence) for this. What is usually taken as the evidence that the rise in CO2 is human-caused ?

1) there is the correlation between the human consumption of fossil fuels and of its concentration in the atmosphere

2) there is the correlation between the decrease of oxygen in the atmosphere and the rise in CO2

3) there is the isotopic composition of CO2 in the atmosphere, which shows that it has a rising component that most probably comes from fossil fuels (lower C-14 content).

However, although this is of course suggestive evidence, this is no proof at all. In order to show this, let us take on a purely imaginary situation. Imagine that the cause-effect relation is different: that a rise in temperature CAUSES a rise in equilibrium atmospheric CO2. I'm not saying that this is the case, or that I have the slightest bit of evidence for this. I'm just indicating a working hypothesis to show the PROOF false. Imagine, as a gedanken experiment, that it is temperature that sets CO2 levels, and not vice versa. Also, one can acknowledge that humanity did indeed produce a lot of CO2 from fossil fuels.

If the temperature were constant and it drives the CO2 equilibrium value, then the equilibrium values of CO2 would remain constant. That means then that there is somewhere a mechanism that takes up or releases CO2 if this amount is changed somehow by an external process. Now, if you burn a lot of fossil fuels, you are going to put much more CO2 in the atmosphere, and the regulatory mechanism will "sink" an equal amount. However, the amount of fossil-fuel related CO2 (tracable with isotope analysis) will then of course rise in the atmosphere: most CO2 will be from fossil-fuel origin, but its LEVEL will be determined by the causal system driven by temperature.
Also, because burning fossil fuels consumes O2, one would see a decrease in O2 on par with the consumption of fossil fuels, and hence with the immediate production of CO2. If the regulatory mechanism driven by temperature has some inertia, one would indeed see, upon a rise in fossil fuel burning, an immediate CO2 rise, and an immediate O2 decrease ; but the CO2 level would then be steered by the control mechanism to its equilibrium value.

Now, imagine that the temperature rises for some or other reason. Now the equilibrium set value of CO2 will rise too. And what would we observe then ? We would observe:
1) a rising equilibrium value of CO2 in the atmosphere
2) a correlation between the CO2 increase in the atmosphere and the O2 decrease in the atmosphere
3) an isotopic composition which indicates that an increasing fraction of the CO2 content in the atmosphere is from fossil fuel origin.

In other words, this gedanken experiment, with its working hypothesis that temperature drives CO2 equilibrium values, is entirely in agreement with observations. That's no proof of course. It is only a proof that these 3 observations DON'T PROVE any causal relationship between rising CO2 levels in the atmosphere and human CO2 production by fossil fuel burning, given that they are also compatible with a model in which this is not assumed.

Again, don't understand me wrong: I didn't say that I proved that human CO2 production is NOT responsible for the rise in CO2 in the atmosphere. I only indicated that the arguments that are advanced as PROOF of this, are not a proof (although, I admit, suggestive), because they can be compatible with a working hypothesis which is the inverse of the to be proven statement.

If you want an analogy, consider that you are on the seaside. It is rising tide but you don't know what a rising tide is. You see somebody poor heavy water in the sea, you see the sealevel rise, and you accuse him of rising the level of the sea. For that, you do an isotopic analysis, and you show that there is more heavy water than usual present in the water that is rising at the shore. You also see that when he poors in a lot of water, the water level rises a bit faster, and when he poors in slower, the water rises a bit slower (on a background of steady rising). From this, you conclude that the guy is making the sealevel rise.

Again, don't understand me wrong. I'm not saying that there is no CO2 rise because of human fossil fuel consumption, that this doesn't lead to AGW, and so on. This is very well possible, and even plausible. But to say that it has been scientifically established requires one to envision ALL POSSIBLE WAYS IN WHICH THIS COULD NOT BE TRUE, and then exclude them one by one, so that only one remains. I DON'T SEE THIS BEING DONE. I rather see a lot of suggestive stuff, but no critical analysis of how all this could not be indicating what it is "supposed to indicate". And that, in my book, is bad science.

[Andre]

But the first thing in greenhouse effect is understanding how it works.

The global warming hypothesis assumes that the difference between basic Earth black body temperature and actual atmospheric temperature is caused by radiative properties of the greenhouse gases, of which water vapor is the most important, basically nullifying all other mechanisms. In reality it is convection and latent heat transport, which heats the atmosphere from the surface at daylight, while there is no comparable mechanism at night to cool it again. So this mechanism is one way only. This can be demonstrated when comparing day and night lapse rates in the atmosphere, where the difference between day and night is greatest at the Earth surface

http://mtp.jpl.nasa.gov/missions/texaqs/austin_poster/Image11.gif

Source (http://mtp.jpl.nasa.gov/missions/texaqs/austin_poster/MTP_Austin_Paper.htm)

Caption:
The figure to the right uses PNNL radiosonde data to show the diurnal variation of temperature profiles for August 31, 2000, at La Marque. The UTC launch times were 0501 (pink), 0758 (red), 1106 (light blue), 1401 (green), 1700 (white), 2000 (yellow) and 2300 (grey). It is clear that ground-level nighttime inversion vanishes between 1401 and 1700 UTC, and reappears after 2300 UTC. Since all but one Electra take off was before 1600 UTC, and all but two landings were after 2300 UTC, it is unlikely that the Electra would have encountered any inversions.


Hence the upper levels hardly cool at night as the only cooling mechanism is .... greenhouse effect, radiation out. And at those levels, with strongly reduced water vapor, radiation escapes to outer space much easier. This effect appears to be neglected in the IPCC endorsed literature and if you don't account for it in the models, you're basically stuck to the GIGO principle.

It is all in this thread, discussing the Chilingar et al 2008 study.

http://www.physicsforums.com/showthread.php?t=252066

In this mechanism the concentration of greenhouse gasses for temperature is strongly reduced. More greenhouse warming simply increases the convection rate, removing the excess heat again from the surface.

[jostpuur]

If you look at those graphs, you see that the direct measurements of temperatures, and other indirect measurements based on tree rings and all that, agree very well during approximately the time 1850-1980. So if the measurements agree on such long interval, and then the reliable direct measurements show dramatic rise in the latest years near 2000, isn't the whole graph genuinely honest and alarming hockey stick then?

[Andre]

If you look at those graphs, you see that the direct measurements of temperatures, and other indirect measurements based on tree rings and all that, agree very well during approximately the time 1850-1980. So if the measurements agree on such long interval, and then the reliable direct measurements show dramatic rise in the latest years near 2000, isn't the whole graph genuinely honest and alarming hockey stick then?

But they do not! Look at the big gap between the measured temperatures and the reconstruction, with and without blade of the hockeystick at the very end. Moreovere the red CRU temperatures hitting the roof at >0.9 degrees is very dishonest Just check the real numbers.

[jostpuur]

I see the gap at the very end, near 2000, but I was pointing out that the measurements agree earlier during somewhat long interval 1850-1980. Of course it is puzzling that there seems to be disagreement in the end, but the reconstructions look like reliable for little bit longer intervals. And on the other hand the direct measurements are reliable for short intervals too. So when you put this together, the entire hockey stick looks pretty reliable.

[Andre]

.... I'm not saying that there is no CO2 rise because of human fossil fuel consumption, that this doesn't lead to AGW, and so on. This is very well possible, and even plausible. But to say that it has been scientifically established requires one to envision ALL POSSIBLE WAYS IN WHICH THIS COULD NOT BE TRUE, and then exclude them one by one, so that only one remains. I DON'T SEE THIS BEING DONE.

The problem with that is if you try for instance albedo and temperature like here (http://www.physicsforums.com/showthread.php?t=256152), you suddenly find a plausible correlation/causation without any CO2:

http://gallery.myff.org/gallery/361122/albedo-temp.GIF

on the other hand if you'd test paleo temperature reconstructions based on CO2 (Van Hoof et al 2008) versus other reconstructions like here (http://www.physicsforums.com/showthread.php?t=262607) the match is rather underwhelming:

http://gallery.myff.org/gallery/355291/mann-vs-vanhoof.PNG

See the problem Jostpuur?

[vanesch]

If you look at those graphs, you see that the direct measurements of temperatures, and other indirect measurements based on tree rings and all that, agree very well during approximately the time 1850-1980. So if the measurements agree on such long interval, and then the reliable direct measurements show dramatic rise in the latest years near 2000, isn't the whole graph genuinely honest and alarming hockey stick then?

The graph (especially the 2001 graph) wanted to display that the dramatic rise in 1990-2000 was exceptional, and wanted to show that never in the last 1000 years, the *level* as well as the *slope* was reached in an obvious and "order of magnitude" way.

The problem is that if this rise is not reproduced in the proxies, then that means that the proxies (for instance through a low-pass filtering effect) don't follow such quick rises, but smoothen them out. And that means that if there have been such "glitches" in the past, we probably won't see them either. So the very fact that the big rise in 1990-2000 wasn't seen in the proxies means that they don't show such quick rises. It isn't a surprise then that they didn't show them in the past, and hence the fact that they don't show them in the past is no proof anymore that they didn't happen, as we have under our very nose an example of when there was a quick rise in the actual temperature and no obvious signal in the proxies. If there had been a similar glitch around the year 1000, the proxies would have reacted as they are reacting now, and wouldn't have followed the temperature glitch. So we don't see it. That's no proof that there hasn't been any.

That the proxies correspond on some time scale with the temperature shouldn't surprise us either, as proxies need to be calibrated. So you need to take some patch in time to set equal measured temperatures and proxy data.

Finally concerning the *level* of the temperatures, contrary to the 2001 plot which indicated a proxy which did show uniform lower temperatures than recently, you clearly see now that different proxies don't agree and that we are completely within the "noise".

[Bored Wombat]

Let us concentrate exactly (we're using indeed the same data :-) on this "hockey stick".

Compare it to the initial hockey stick on p 3 of
http://www.ipcc.ch/pdf/climate-changes-2001/scientific-basis/scientific-spm-en.pdf

the summary for policy makers in 2001.

Now, admit that there is a world of difference in the convincing power that we are *on an exceptional and dramatic temperature rise* which was the aim of that plot (with well-choosen coloring too) in the last century - a rise that was OBVIOUSLY an order of magnitude larger than what had happened in the last 1000 year.

Certainly the emphasis of the average estimate rather than the range of error does more to create that impression, but the reconstructions are all largely similar.

An average line on this graph would do the same thing.

There is another error in the presentation of the 2007 plot. That is the visual confusion (using well-chosen coloring) of the proxy data and the actual measurements. Clearly, the proxy data are not 100% the same as the actual measurements (the solid black curve doesn't coincide perfectly with the proxies). That means that there is a dynamical system in between both, which can be for instance, a low pass filter.

More likely a more limited global coverage.


Even better: shift the instrument data and the smooth grey curve back about 1000 years. You'd find about equal agreement.
Not if you let your eye average the temperatures a little. There are four proxies up by the Mann et al. curve, and only two down by the D’Arrigo et al. curve. You'd guess a 0.2°C of warming occurred then. Whereas now we have four times that.

Leave away the current data (which are not the same as the proxies), and show only the proxies. Do you think that this still has the "hockey stick" conviction power ? You only see a smooth rising before 1000 AD, then a dip and indeed a slightly stronger rise in the last century. NOTHING TO DO with the dramatic effect displayed in the 2001 report. Where is the scientific honesty here ?
I think the data is pretty similar.

[Bored Wombat]

Important is the observation that the blade of these hockeystick is glued upon it and that the proxies are not following which basically already refutes the robustness of these proxies.
Has there been a scholarly response to the paper to that effect?
I see that the recent climate change has been sudden, and that the proxies don't tend to extend into the modern era.

But there is more, Mann et al 2008 (http://www.pnas.org/content/early/2008/09/02/0805721105.full.pdf) admit that the adbundantly used and recycled tree ring proxies are basically flawed by showing the difference in skill in fig 2:
Sorry, I can't find that admission. Where is it?

[Bored Wombat]

The global warming hypothesis assumes that the difference between basic Earth black body temperature and actual atmospheric temperature is caused by radiative properties of the greenhouse gases, of which water vapor is the most important, basically nullifying all other mechanisms.
If it doesn't nullify all other mechanisms, but works additionally to them, then there would still be an effect on climate if greenhouse gasses are increased in atmospheric concentration.

And the four paleohistorical papers estimating past climate sensitivity above do show that historically at least there has been a climate sensitivity of about 3°C per doubling of CO2.

Surely if convection were nullifying the greenhouse effect now it would have also done it in the past?

[vanesch]

I think the data is pretty similar.

It is not just about the data, it is about the presentation, which has been set up graphically to "make the point".

And just taking averages doesn't do the thing, exactly for the reasons I explained. Let us not forget that the aim of that plot is NOT to show that there has been a recent rise - we wouldn't need proxies for that, it is in the instrumental data. Yes, there has been a temperature rise of the last few decades.

The point the plot wanted to make, and its visual representation did so extremely well in the 2001 plot, was that this rise was *exceptional* and hadn't occured (or any similar change hadn't occured) in the last 1000 years or so, and even longer. It also wanted to make another point, that the value of the current temperature was also *much* higher than any value reached in the last 1000 years.

However, what we clearly see is that the proxies don't follow the quick rise now - even though they are probably "tuned" to do so, as proxies need to be calibrated, and hence have some part of the current instrumental data record used in their calibration to determine absolute value and sensitivity to variations.
One shouldn't therefor be surprised that *all proxies* more or less coincide over a lapse of instrumental record: it has been used for their calibration ! That explains 1) their good correlation to the instrumental record from 1850 - 1950 and 2) the smallness of their variability over that period: they just re-emit their calibration. It is already a problem that they don't reconstruct the quick instrumental rise in the last decades. So they already don't represent correctly "short term dynamics".
Their divergence in the past then indicates the differences in dynamics and the lack of 100% correlation with temperature. This is not necessarily statistical noise which averages out to 0. So taking averages doesn't provide you necessarily with a *less biased* estimator, and certainly not with a *dynamically more accurate* estimator.

Imagine that their correlation with temperature and with its dynamics is relatively poor. If you have several of those, with different correlations, and you average them out, chances are that you will find a more or less constant value. You might have even degraded the correlation with temperature. You might not have a thermometer at all. The "good" correspondence in 1850 - 1950 simply comes then by forcing the calibration: they all reproduce their calibration curve.

This is why the visual representation of the 2007 data, WITHOUT the instrument record, gives you the most faithful reconstruction of temperature through these proxies: one gets an idea of the accuracy of the proxy measurements, and one gets an idea of the overall dynamics. Well, if you do that, there's nothing that *clearly* indicates an *exceptional* rise in the last few decades, and an *exceptional level*. Of course, there is a rise, and of course temperatures are high, but the overall impression is that they reach about the same level as 1000 years ago, and that between that period and now, there have been periods of cooling, and of heating, very comparable to what happens now.

Those data, and their honest representation (without the instrumental data) don't convince anybody that something very alarming is going on right now, and if you see something else in that, then I don't know what you see. If these were interest rates of different banks, would you panic right now ? More to the point, doesn't the current situation, described with the proxies, ressemble the situation just before 1000 ?

In other words, the proxy data don't *prove* that no such rise has taken place in the past, or that the current levels are exceptionally higher. They *simply don't contain that information*.

[Bored Wombat]

Well, again, there is no tight proof (although there is suggestive evidence) for this. What is usually taken as the evidence that the rise in CO2 is human-caused ?

1) there is the correlation between the human consumption of fossil fuels and of its concentration in the atmosphere
Yes. About half of the CO2 released by fossil fuels combustion remains in the atmosphere.

The bulk of the remainder is dissolved in the oceans, and it's movement there can be traced. (Because it has different Isotope rations from the background, and everything since 16th July 1945 had higher radioisotopes).

2) there is the correlation between the decrease of oxygen in the atmosphere and the rise in CO2
Yes. Anticorrelation. Showing that the extra CO2 is from the combustion of something. Perhaps forests.

3) there is the isotopic composition of CO2 in the atmosphere, which shows that it has a rising component that most probably comes from fossil fuels (lower C-14 content).
Yes, also lower C-13 content, showing it is from organic origin. Together with the lower C-14 content we have it locked to fossil fuels.

This is direct evidence that can be compared with the (strong) circumstantial evidence that we have released more than enough CO2 into the atmosphere to affect the change in atmospheric concentration.

However, although this is of course suggestive evidence, this is no proof at all.
Well, we know where the CO2 came from.

The reason it remains in the atmosphere is about the capacity and kinetics of the world's oceans and terrestrial biosphere to sink it.

And the oceanic one is probably inversely proportional to temperature. As ice ages ends, it seems as if about 800 years after the warming begins, the oceans start outgassing CO2. So in about 2700AD, they're going to have another positive feedback kick in, and they're not going to have our main sink for CO2.

And we have seen that the CO2 levels started coming up before 1900, but temperatures didn't rise until after that, so I think we know what the atmospheric CO2 concentration has initially been more dependent on the emission of CO2 into the atmosphere than an increase in temperature.

But the oceanic sink for CO2 is under much study, and seems to be at about 1/3rd of it's long term capacity, and it showing signs of slowing slowing (proportionally speaking ... it is still absorbing more than ever linearly speaking, but emissions are increasing faster than that). And it is temperature (and wind) dependent. But despite the nature of the world's carbon sinks, we know what the source is ... the combustion of fossil fuels.

[Bored Wombat]

The problem with that is if you try for instance albedo and temperature like here (http://www.physicsforums.com/showthread.php?t=256152), you suddenly find a plausible correlation/causation without any CO2:
We do know that CO2 is a greenhouse gas. So we have causation there as well. Albedo will certainly make a difference as well. But that does not discount the last 100 years of optics.

[Bored Wombat]

The problem is that if this rise is not reproduced in the proxies, then that means that the proxies (for instance through a low-pass filtering effect) don't follow such quick rises, but smoothen them out.

We know that not to be the case, because we know from proxy data the the warming at the end of the Younger Dryas (11550 calendar years BP) was quicker than the warming we see now.

So rapid climate change more rapid than current can be inferred from proxy data.

[jostpuur]

The graph (especially the 2001 graph) wanted to display that the dramatic rise in 1990-2000 was exceptional, and wanted to show that never in the last 1000 years, the *level* as well as the *slope* was reached in an obvious and "order of magnitude" way.

The problem is that if this rise is not reproduced in the proxies, then that means that the proxies (for instance through a low-pass filtering effect) don't follow such quick rises, but smoothen them out. And that means that if there have been such "glitches" in the past, we probably won't see them either.

Assuming that what you say here is correct, I have two comments:

One: While this point is valid, this point didn't quite become clear in the Andre's post where he showed the hockey stick with direct measurements removed, and spoke about scientific honesty. It looked like he was setting the resent temperature rise under question, which is quite different from saying that reconstructions would have smoothened out possible spikes already earlier.

Two: While the possible existence of earlier spikes cannot be denied by using the temperature reconstructions, on the other hand, the resent temperature rise has been modeled by taking into account the man made greenhouse emissions. So isn't it then quite unlikely, that the resent temperature rise would be only a one natural spike among the many other spikes that we don't see?


In other words, the proxy data don't *prove* that no such rise has taken place in the past, or that the current levels are exceptionally higher. They *simply don't contain that information*.

But are you trying to say, that convincingly alarming information wouldn't exist?

[Bored Wombat]

However, what we clearly see is that the proxies don't follow the quick rise now - even though they are probably "tuned" to do so, as proxies need to be calibrated, and hence have some part of the current instrumental data record used in their calibration to determine absolute value and sensitivity to variations.
How do you know that we're not just seeing the modern edge of the proxy data?
That is what I assumed from the graph.

[vanesch]

Yes. About half of the CO2 released by fossil fuels combustion remains in the atmosphere.

The bulk of the remainder is dissolved in the oceans, and it's movement there can be traced. (Because it has different Isotope rations from the background, and everything since 16th July 1945 had higher radioisotopes).


Yes. Anticorrelation. Showing that the extra CO2 is from the combustion of something. Perhaps forests.


Yes, also lower C-13 content, showing it is from organic origin. Together with the lower C-14 content we have it locked to fossil fuels.

This is direct evidence that can be compared with the (strong) circumstantial evidence that we have released more than enough CO2 into the atmosphere to affect the change in atmospheric concentration.



I acknowledged that. I only pointed out that there is a difference between the ORIGIN of the actual CO2 in the atmosphere (partly from fossil, no doubt), and its LEVEL, which can be set or not by a regulation mechanism. The two have nothing to do with each other (see my simplistic analogy with heavy water and the tide rise).

Another example: is it because most of my pocket change comes from the local supermarket that they are the ones who determine how much money I have ?



Well, we know where the CO2 came from.


Yup. I didn't dispute that.


The reason it remains in the atmosphere is about the capacity and kinetics of the world's oceans and terrestrial biosphere to sink it.


THAT is the real "level setter". This has nothing to do with what is the origin of (part of) atmospheric CO2 - which is undeniably from fossil fuels.

So if you want to infer that the atmospheric CO2 LEVEL is changing by a specific external source (fossil fuel burning), then you have to demonstrate that the regulatory mechanism is OVERWHELMED by this source. THAT would be an indication. But as you say yourself, this is not clear at all. This is possible, but this has not been demonstrated beyond doubt - and the actual arguments here are not even presented as the real arguments. Instead, as "proof", is presented something which discusses the ORIGIN, but not the LEVEL.

Especially because all proportions taken into account, the amount of fossil-fuel CO2 is small compared to the entire inventory of CO2 in the circuit (as the amount of heavy water poored in was small as compared to the amount of water in the sea).


And the oceanic one is probably inversely proportional to temperature. As ice ages ends, it seems as if about 800 years after the warming begins, the oceans start outgassing CO2. So in about 2700AD, they're going to have another positive feedback kick in, and they're not going to have our main sink for CO2.


Or, it might be that it is TEMPERATURE that drives the CO2 level, and not vice versa. If it is temperature which determines CO2 level, then any external CO2 source (which remains small compared to the total inventory of CO2 in the circuit). In that case, it is not "feedback", but just "following the set level", and the temperature might, or might not, be mainly steered by CO2 content.


And we have seen that the CO2 levels started coming up before 1900, but temperatures didn't rise until after that, so I think we know what the atmospheric CO2 concentration has initially been more dependent on the emission of CO2 into the atmosphere than an increase in temperature.


And then there are paleo data where the time correlation is the opposite (temperature rises first, and then CO2 follows - although this was first presented the other way around).

Hey, human computing power also started rising before temperature rose. Is computing power therefor a drive of global temperature.

A correlation is not a causal link per se. It could be, but it could also not be.


But the oceanic sink for CO2 is under much study, and seems to be at about 1/3rd of it's long term capacity, and it showing signs of slowing slowing (proportionally speaking ... it is still absorbing more than ever linearly speaking, but emissions are increasing faster than that). And it is temperature (and wind) dependent. But despite the nature of the world's carbon sinks, we know what the source is ... the combustion of fossil fuels.

Yes, this is still under study.

Again, I'm NOT arguing that there is no AGW, and that human-caused fossil fuel combustion has nothing to do with it. Far from it. Actually I'm a long-term nuclear power proponent and it is one of my main reasons. But with all I have read, I find more reasons to doubt the scientific certainty that is displayed more than anything else.

What I am objecting to in this whole business is that the ARGUMENTATION IS ALL WRONG. About all arguments presented as scientific proof beyond reasonable doubt are LOGICALLY ERRONEOUS or factually misrepresented. What scares me is that these ELEMENTARY objections - I'm not a climate scientist - are not even adressed, and that nobody in the entire community points this out - as if it were wrong to be critical towards the credo.

[vanesch]

How do you know that we're not just seeing the modern edge of the proxy data?
That is what I assumed from the graph.

But I'm not the one claiming "scientific proof". This is my whole argument. Scientific proof means: "we've eliminated beyond doubt all other reasonable explanations". So where is your PROOF that we are seeing the modern edge of proxy data, and that *there doesn't exist any other reasonable explanation* for it ? THEN you have a case. Now, you only have suggestive evidence. Which I acknowledge.

[vanesch]

We do know that CO2 is a greenhouse gas. So we have causation there as well. Albedo will certainly make a difference as well. But that does not discount the last 100 years of optics.

We don't know what is the *real effect* of CO2. There is circular reasoning here. Of course I don't doubt that CO2, in a stationary atmosphere, has a radiative heating effect. That's given by MODTRAN for instance, and its effect is small. All the rest: effects on convection, on water vapor, on land response, on ocean currents, on whatever, are complicated problems, and it is not clear what the total effect is. So the "physical/chemical" effect of CO2, as a greenhouse gas, is, in very idealized circumstances, limited to the about 0.5 - 1 degree for a doubling, given by MODTRAN.

And then the reasoning becomes circular: 1) BECAUSE we see a correlation, recently, between rising CO2 levels and temperature, this must be caused by CO2, so this is then: observation --> strong greenhouse gas effect and 2) because CO2 is a strong greenhouse gas, this proves that the correlation observed is a causal effect.

But this has nothing to do with the small greenhouse effect of CO2 in an idealised atmosphere as shown by MODTRAN. You can't at the same use observations to prove that CO2 is a strong greenhouse gas (under the assumption that there is a causal link), and then use that conclusion to show that there was a causal link. In other words, you take as a premise, the conclusion you want to reach, and then, no wonder, you arrive at some elements that confirm your hypothesis.

[Bored Wombat]

Another example: is it because most of my pocket change comes from the local supermarket that they are the ones who determine how much money I have?
That analogy is inappropriate, because there are only 3 sources or sinks of fossil fuels. Human activity, the oceans, and the terrestrial biosphere. The source of the atmospheric increase is from fossil fuels.

There's no equivalent of your investments or salary in this system.

THAT is the real "level setter". This has nothing to do with what is the origin of (part of) atmospheric CO2 - which is undeniably from fossil fuels.
Well, as you say you have no evidence for that.

Whereas we know that in the past for approximately current temperatures, CO2 concentratiions should be about 300 or 320ppm, not 385ppm:

http://www.ncdc.noaa.gov/paleo/pubs/luethi2008/fig2.jpg (http://www.ncdc.noaa.gov/paleo/pubs/luethi2008/luethi2008.html)

So we know that it is not caused by temperature.

Especially because all proportions taken into account, the amount of fossil-fuel CO2 is small compared to the entire inventory of CO2 in the circuit
But it is large compared to the increase in atmospheric concentration.


And then there are paleo data where the time correlation is the opposite (temperature rises first, and then CO2 follows
Right. So we know that the current warming is not like the ends of past ice ages, because the CO2 has moved first.

Which fits with our other understandings, because Homo Neanderthalensis didn't have coal mines.

- although this was first presented the other way around).
You claim that this was known and held back from publication? I recall a paper talking very tentatively about it. It seemed to me that it was published as soon as it was noticed. Of course the age of the air in an ice core (from which the atmospheric CO2 concentration is measured) is younger than the age of the ice (from which local temperature at the time of freezing is inferred), so they had reason to state it tentatively.

From what do you claim that this finding was held back?

Hey, human computing power also started rising before temperature rose. Is computing power therefor a drive of global temperature.

A correlation is not a causal link per se. It could be, but it could also not be.
That is true, but in this case the causal link is known and understood. It is the greenhouse effect.

[vanesch]

One: While this point is valid, this point didn't quite become clear in the Andre's post where he showed the hockey stick with direct measurements removed, and spoke about scientific honesty. It looked like he was setting the resent temperature rise under question, which is quite different from saying that reconstructions would have smoothened out possible spikes already earlier.


I'm not Andre :-) Andre thinks that there is no AGW. I'm agnostic about AGW, I'm only indicating that what is presented - especially by the IPCC - is not scientifically rigorous as Feynman would have liked it, in that one would have tried to show oneself wrong. On the contrary, the IPCC is built up as an argument for AGW, not as a critical scientific analysis. I surely find much material presented by the IPCC very suggestive, but one should then be aware that it was presented TO MAKE A CASE, and not as a scientific analysis. Nevertheless, it is always presented as if it were the ultimate scientific analysis that PROVES AGW beyond doubt, and anyone being critical towards it is almost seen as a crackpot (or a heretic?).

This is like listening to the lawyer or listening to the judge. The lawyer builds a case. The judge tries to see the truth. When the lawyer is confused with the judge, truth is lost.

I'm just trying to see the holes in the lawyer's argument - as a judge would do.


Two: While the possible existence of earlier spikes cannot be denied by using the temperature reconstructions, on the other hand, the resent temperature rise has been modeled by taking into account the man made greenhouse emissions. So isn't it then quite unlikely, that the resent temperature rise would be only a one natural spike among the many other spikes that we don't see?


Yes, and those models are built exactly upon effects by CO2 as taken from these data. That's the circular reasoning I pointed towards in another post here.


But are you trying to say, that convincingly alarming information wouldn't exist?

I think there is more than enough SUGGESTIVE information to be indicative that the hypothesis of AGW is a plausibility, and given its potential disastrous effects, I think that until we find out more, we should take this into account in our policies.

However, "alarming" and "scientifically sound" are not the same. I think the scientific case for AGW is far from closed, and I wouldn't be surprised that it turns out not to be there, or be there to a much lesser extend than claimed now. It could also be there the way people present it. But the honest answer is that we don't know yet. Let us say that most of the material presented by things such as the IPCC is not INCOMPATIBLE with the existence of AGW - but you would not expect otherwise from a lawyer's case, would you ?
I am appalled at the fact that many "proofs" presented by the IPCC have logical holes in them which are not adressed.

When presenting AGW AS IF IT WERE A SCIENTIFIC FACT BEYOND DOUBT - which I try to show it isn't - we are committing scientific dishonesty.

[Bored Wombat]

But this has nothing to do with the small greenhouse effect of CO2 in an idealised atmosphere as shown by MODTRAN. You can't at the same use observations to prove that CO2 is a strong greenhouse gas (under the assumption that there is a causal link), and then use that conclusion to show that there was a causal link. In other words, you take as a premise, the conclusion you want to reach, and then, no wonder, you arrive at some elements that confirm your hypothesis.

This is correct to within certain boundaries.

The climate sensitivity might be as low as 1.5 or 1.6°C per doubling of CO2, or it might be as high as 5.5 or even 6°C per doubling. But outside that range it just doesn't fit the observational and paleohistorical data.

So yes, it is poorly known, for the reason you describe, but you exaggerate the effect of this uncertainty. Even a 1.5°C per doubling, with the increase in CO2 concentration since the anthropogenic ear of 385/280 = 1.375 or 0.46 doublings gives a warming of 0.69°C due to CO2 increase alone. Which is probably most of the observed warming, even taking into account that 60% of the climate's response to an increase in radiative forcing isn't complete for 25-50 years (the large error here due again to the error in climate sensitivity to CO2 - so it will be shorter times if climate sensitivity is low.)

The bottom line is that we certainly don't know it all, but we do know that the current warming is very likely to be mostly anthropogenic.

[vanesch]

That analogy is inappropriate, because there are only 3 sources or sinks of fossil fuels. Human activity, the oceans, and the terrestrial biosphere. The source of the atmospheric increase is from fossil fuels.


But do you know their reactions to other parameters like temperature accurately enough as to be able to show that the difference is DRIVEN by the fossil-fuel consumption ? The source of atmospheric CO2 is partly from fossil fuels, but do you know precisely how oceans and land are reacting to CO2 concentrations and cannot act as a regulator ?


There's no equivalent of your investments or salary in this system.


Can't oceans or the terrestrial biosphere be "sources" in the sense of being less of a sink than they used to be just because of regulation properties ? Imagine that oceans "want" to have a higher level of atmospheric CO2 for one or other reason. If there wouldn't be any fossil fuel production, they would then outgas more CO2. Because there is fossil fuel CO2, they don't outgas as much, but they even take up some. But they still set the level.


Well, as you say you have no evidence for that.


I don't have to. YOU are making a case. You have to show that no such evidence can exist. That's my point. Before you have a proof, you have to have explored all possible other explanations.


Whereas we know that in the past for approximately current temperatures, CO2 concentratiions should be about 300 or 320ppm, not 385ppm:

http://www.ncdc.noaa.gov/paleo/pubs/luethi2008/fig2.jpg (http://www.ncdc.noaa.gov/paleo/pubs/luethi2008/luethi2008.html)

So we know that it is not caused by temperature.


It is not caused by temperature, but then it comes 600 years (I think? From the top of my head) AFTER the temperature increase, and is almost perfectly correlated. This isn't directly a demonstration that CO2 DROVE temperature. If anything causal here, it is temperature which drives CO2.
So you are just talking about the quantitative effect. The world is different now. Land usage is different. The response might be different. The exact dynamics hasn't been elucidated. It is not because you've seen a different response in the past that this is a PROOF that this time the quantitatively different response (in as much as the proxies are numerically accurate) is FOR SURE not caused partly by temperature. That could only be the case if you have a perfect physical dynamical model of the relationship between temperature, land usage and CO2 content. Hell, the proxy might even have a cross-correlation! Maybe the proxy for CO2 calibration is partly dependent on temperature or vice versa. How can you know ?


But it is large compared to the increase in atmospheric concentration.


Yes, if you can quantitatively demonstrate that the regulatory mechanisms are overwhelmed, then indeed this indicates that fossil fuel combustion contributes - at least temporarily - to the atmospheric CO2 concentration. But the ARGUMENTS PRESENTED don't prove this. This is my point.


Right. So we know that the current warming is not like the ends of past ice ages, because the CO2 has moved first.


Nevertheless, before the 600 year shift was known, these data were presented as PROOF THAT CO2 DROVE TEMPERATURE. It was one of those "undeniable proofs" which fell on their face.


Which fits with our other understandings, because Homo Neanderthalensis didn't have coal mines.


This is again taking your conclusion as an argument. You ASSUME that it is human-driven CO2 which is now the main cause of rising of atmospheric CO2, and you analyse paleodata using this, and then you arrive to the conclusion that, well, it must be human-driven CO2 which is now the main cause of rising atmospheric CO2. Again, the only real proof would be if you had a very good physical model which could predict CO2 responses as a function of temperature (NOT using these paleodata of course), and then if you could predict these effects, and show that it also explains current rise as a function of fossil-fuel combustion. Just fitting a dynamical black box model to paleo data, and seeing the difference with now, is no proof. It is at most suggestive.


You claim that this was known and held back from publication? I recall a paper talking very tentatively about it. It seemed to me that it was published as soon as it was noticed. Of course the age of the air in an ice core (from which the atmospheric CO2 concentration is measured) is younger than the age of the ice (from which local temperature at the time of freezing is inferred), so they had reason to state it tentatively.


I don't mean any intentional dishonesty. I only see that those same data were once used as a "proof" that CO2 drove temperature. Another "hockeystick" if you want. And then it turned out to be the other way around.

At no point I have seen the IPCC hammering that their previous argument was ERRONEOUS and turned out to be FALSE. I'm not claiming that the finding was withheld, I'm only pointing out the difference in publicity that was given to the CO2 --> temperature correlation and then the fact that it was discovered that this was backward.



That is true, but in this case the causal link is known and understood. It is the greenhouse effect.

The problem is that this is again circular: it is used as a PROOF for the greenhouse effect, and at the same time it is EXPLAINED BY that greenhouse effect.

[vanesch]

So yes, it is poorly known, for the reason you describe, but you exaggerate the effect of this uncertainty. Even a 1.5°C per doubling, with the increase in CO2 concentration since the anthropogenic ear of 385/280 = 1.375 or 0.46 doublings gives a warming of 0.69°C due to CO2 increase alone.


MODTRAN gives you less than this: http://www.physicsforums.com/showpost.php?p=1358505&postcount=2

Andre calculated this, and I also did the exercise myself. You get 0.77 K per doubling of CO2.

So even the 1.5 degree per doubling is not clear, unless you *assume* that current temperature increase is *entirely* due to human driven effects, and then after the fact you use this number to *prove* that it is human-caused.


The bottom line is that we certainly don't know it all, but we do know that the current warming is very likely to be mostly anthropogenic.

I have seen suggestive evidence for this in the sense that some observations are compatible with this hypothesis. However, most stuff I've seen as a *proof* seem to me far from being a proof, often logically flawed, and very often circular. This is exactly what you would expect if you take "suggestive evidence compatible with" and try to turn that into "proof that it can only be this" because the logic behind both is different. If you take suggestive evidence, you START with your working hypothesis, and you DERIVE certain properties which are then confronted with data. In as much as the data don't contradict this, you haven't falsified your hypothesis, and hence the evidence is *suggestive*. That's ok. However, when you take observations which are taken as PROOF of certain aspects of your working hypothesis, you don't work that way: you try to find all alternative reasonable working hypotheses, and you try to show that all those alternatives are definitely falsified by current data. In doing so, you cannot mix of course your preferred working hypothesis in the falsification, and that's what is very often done.

[Andre]

I think that the scientific method is a bit comparable with the battle in court, is the defendant innocent or guilty? There can be an abundance of evidence for guilty. But only one is enough to prove innocence. There can be a motive, an opportunity, a lack of alibi, found objects, etc, etc. But if the DNA doesn't match, it's all over, innocent, period!

You can fill threads and threads with melting glaciers, sea levels, arctic sea ice, polar bears, and anything else that seems to be caused by global warming (http://www.google.com/search?hl=en&q=%22global+warming+is+causing%22&btnG=Search&lr=) but if there is only one single piece of evidence that CO2 did not do the job, it's all over, innocent, period!

That evidence, as Vanesch indicated is in the century scale CO2 lag in the ice cores. Now the standard but wrong response of the 'Eco warriors' is "<yawn> and <sigh> How many hundred times have we explained that it's the positive feedback, something causes the temperatures to go up, the warming oceans release CO2 and this takes over the warming effect from the original cause".

No, it does not and the last glacial transition proofs that, provided that we accept that the variation in isotopes is a valid paleo thermometer and that the actual CO2 concentrations reflect the concentrations in the past. I explained that in this thread (http://www.physicsforums.com/showthread.php?t=162192).

http://gallery.myff.org/gallery/145233/epica5.GIF
(details about the data in that same thread (http://www.physicsforums.com/showthread.php?t=162192).)

In this isotope (temperature) versus CO2 plot during the last glacial transition between 20,000 and 10,000 years ago, the century scale CO2 lag is clearly visible. But the assumed positive feedback of CO2 is proven non-existent by the lack of acceleration as the CO2 starts to rise and the abrupt temperature reversal just prior to 14,000 years ago. The continuing CO2 rise because of the lag, should have slowed down that reversal with a weak positive feedback or it should have prevented it completely with a strong positive feedback. It did not, actually it did nothing, it just followed the 'temperature' drop submissively. Hence this demonstrates that changing CO2 concentrations have no noticable effect on the 'temperature'.

Although the math isn't easy, it's pretty simple to make a basic model in excel of feedback effects. This shows roughly how the temperature response might have been with a weak positive feedback of CO2:

http://gallery.myff.org/gallery/145238/pos-feedback2.GIF

Notice how the temperature forcing down, halfway, is barely noticed in the output

But the assumption that the ice ages show a bipolar postive feedback effect, with stable extremes, like flip flops, require a strong positive feedback loop with a total gain >=1. That would lead to something like:

http://gallery.myff.org/gallery/145235/pos-feedback1.GIF

We see the accelerating of 'temp response' kicking in at around 6-7 time units compared to the basic forcing and furthermore, we see no reaction of 'temp response' whatsoever on the sudden reversal of the basic forcing function around time 24. This is about how the CO2 and isotope plot should have looked like, without reversal due to the strong positive feedback of CO2 warming up afterwards. Since it does not, it proves that CO2 did not do that warming and if it didn't do it then, there is no reason to expect that it does now.

The simple basic excel model can be downloaded here (http://gallery.myff.org/gallery/145234/positive-feedback.xls). You could play with the CO2 gain factor between 0 and 1 to see the effect of weak and strong feedback.

[vanesch]

Andre, what one can conclude from that plot is the following:

- grossly, CO2 levels follow temperature, with a lag of a few hundred years, in as much as the proxies used for that aren't cross-influenced themselves, and the time calibration is ok - I'm absolutely not qualified to look into that.

- it is not easy to find a dynamical model that explains one driving the other, except for that gross observation, but as you show, there doesn't seem to be any strong feedback coupling between both - we simply seem to have one variable grossly following the other one with a serious time lag, and this correlation is not there when looking at detailled small dynamics.

- it is very well possible that other factors also influenced CO2, temperature, or the calibration of the proxies.

So *if* there is a causal effect to be deduced from this, which is risky given the above qualifiers, then it is that temperature drives CO2, but not just temperature. It is also possible that both temperature and CO2 are driven by another external cause - but again not in perfect sync.

It is also possible that both of them are part of a very much more complicated dynamical system, but without knowledge of other state variables, it will then be impossible to find any dynamical black box model, and even more difficult, any physical model describing causal relationships.

[Bored Wombat]

But do you know their reactions to other parameters like temperature accurately enough as to be able to show that the difference is DRIVEN by the fossil-fuel consumption ?
I know that it is coming from fossil fuel combustion, and the bulk of it is remaining in the atmosphere with the second largest lump dissolving in the oceans.
And I know that if you increase the partial pressure of a soluble gas, then more of it will dissolve in the oceans.

Can't oceans or the terrestrial biosphere be "sources" in the sense of being less of a sink than they used to be just because of regulation properties ?
That's not the usual meaning of source, but the oceanic efficiency as a sink is dropping. I can't speak for the terrestrial biosphere.

Imagine that oceans "want" to have a higher level of atmospheric CO2 for one or other reason.
By what sort of mechanism?

I don't have to. YOU are making a case.
Okay, my case is that the oceans don't want anything. They'll outgass if the solubility for CO2 decreases, and otherwise dissolve some of any atmospheric increase and release some of any atmospheric decrease. This is how water behaves.

It is not caused by temperature, but then it comes 600 years (I think? From the top of my head) AFTER the temperature increase, and is almost perfectly correlated. This isn't directly a demonstration that CO2 DROVE temperature. If anything causal here, it is temperature which drives CO2.
They are certainly both going on, and we know this not by looking at the graph, but because the physics is understood. CO2 is a greenhouse gas, and it's solubility decreases with increasing water temperature at least around the sort of temperatures that the oceans are.

So you are just talking about the quantitative effect. The world is different now. Land usage is different. The response might be different.
Most of the response is from the oceans. Land usage doesn't affect that.

The exact dynamics hasn't been elucidated. It is not because you've seen a different response in the past that this is a PROOF that this time the quantitatively different response (in as much as the proxies are numerically accurate) is FOR SURE not caused partly by temperature.
Beyond all reasonable doubt.

That could only be the case if you have a perfect physical dynamical model of the relationship between temperature, land usage and CO2 content.
No, I know from the fact that all the CO2 is coming from fossil fuel combustion, and that most of what is not remaining in the atmosphere is dissolving in the oceans, therefore the terrestrial biosphere is not setting the level of atmospheric CO2. It is largely set by an interaction between human activity and the oceans.
Hell, the proxy might even have a cross-correlation! Maybe the proxy for CO2 calibration is partly dependent on temperature or vice versa. How can you know ?
Sorry, what proxy are we talking about here?

Nevertheless, before the 600 year shift was known, these data were presented as PROOF THAT CO2 DROVE TEMPERATURE. It was one of those "undeniable proofs" which fell on their face.
Where is it called an "undeniable proofs"? It is certainly true that a doubling of CO2 results in warming of over 1.5°C robustly throughout the last 420 million years. Is that what you mean by "drives" temperature?

This is again taking your conclusion as an argument. You ASSUME that it is human-driven CO2 which is now the main cause of rising of atmospheric CO2,
Well, I don't think it is really an assumption, because we know where it comes from, and we know that it's concentration is 30% above what it normally peaks at during an interglacial, so we know well enough that this level is not due to some natural mechanism.
And I think it strange that we are looking for such a mechanism.
"We're putting 11Gt of Carbon into the atmosphere every year, but where is this 7Gt of carbon that is accumulating in the atmosphere every year coming from?" It doesn't seem to be that worthwhile a question to dwell on.

But if you consider the paleoclimatic reconstructions, I think there is sufficient support for the surely obvious to convince most juries beyond all reasonable doubt.

Just fitting a dynamical black box model to paleo data, and seeing the difference with now, is no proof. It is at most suggestive.
What black box is this?

I don't mean any intentional dishonesty. I only see that those same data were once used as a "proof" that CO2 drove temperature. Another "hockeystick" if you want. And then it turned out to be the other way around.

At no point I have seen the IPCC hammering that their previous argument was ERRONEOUS and turned out to be FALSE. I'm not claiming that the finding was withheld, I'm only pointing out the difference in publicity that was given to the CO2 --> temperature correlation and then the fact that it was discovered that this was backward.

I don't mean any intentional dishonesty. I only see that those same data were once used as a "proof" that CO2 drove temperature. Another "hockeystick" if you want. And then it turned out to be the other way around.
It's not the other way around. They move simultaneously for the most part.

At no point I have seen the IPCC hammering that their previous argument was ERRONEOUS and turned out to be FALSE.
Do you have an example of this previous argument in the words of the IPCC that was erroneous?

The problem is that this is again circular: it is used as a PROOF for the greenhouse effect, and at the same time it is EXPLAINED BY that greenhouse effect.
You don't need to prove the greenhouse effect, it is a result of well understood optics. It has been proven a century or so. The world would average a chilly -15°C without it.

[Andre]

Andre, what one can conclude from that plot is the following:

- grossly, CO2 levels follow temperature, with a lag of a few hundred years, in as much as the proxies used for that aren't cross-influenced themselves, and the time calibration is ok - I'm absolutely not qualified to look into that.

It's okay, it's data from abundantly peer reviewed literature and the logic seems okay too as oceans are extremely inert thermally, a few centuries is nothing, but...it's their interpretation not mine.

- it is not easy to find a dynamical model that explains one driving the other, except for that gross observation, but as you show, there doesn't seem to be any strong feedback coupling between both - we simply seem to have one variable grossly following the other one with a serious time lag, and this correlation is not there when looking at detailled small dynamics.

Right, but we do know the difference in dynamic responses between positive and negative feedback loops, with as shown lazy behavior of positive feedback loops, unwilling to change heading and move further away from the equilibrium (unstable) whereas negative feedback loops shows the opposite, with a trend to resist change and return to equilibrium (stable). This effect has been explored statistically in various ways by Olavi Kärner (one of the authors of the Independant Summary of Policy Makers). He invariably finds negative feedback which gives no support to the AGW hypothesis. His publications here (http://www.aai.ee/~olavi/). One might wonder why Naomi Oreskes did not find these studies.


It is also possible that both of them are part of a very much more complicated dynamical system, but without knowledge of other state variables, it will then be impossible to find any dynamical black box model, and even more difficult, any physical model describing causal relationships.

That's what I'm after the last couple of years and I bet my money on that. Unfortunately we have to sit out the AGW political ideology before we can progress again, as Richard Lindzen proposes here (http://arxiv.org/ftp/arxiv/papers/0809/0809.3762.pdf).

[Andre]

Bored Wombat, I said

I think that the scientific method is a bit comparable with the battle in court, is the defendant innocent or guilty? There can be an abundance of evidence for guilty. But only one is enough to prove innocence. There can be a motive, an opportunity, a lack of alibi, found objects, etc, etc. But if the DNA doesn't match, it's all over, innocent, period!

You can fill threads and threads with melting glaciers, sea levels, arctic sea ice, polar bears, and anything else that seems to be caused by global warming (http://www.google.com/search?hl=en&q=%22global+warming+is+causing%22&btnG=Search&lr=) but if there is only one single piece of evidence that CO2 did not do the job, it's all over, innocent, period!

And then I demonstrated that the fingerprint did not match, hence there is evidence that CO2 did not do the job, hence, it's all over, innocent, period! So what use is it to continue talking about "motive, an opportunity, a lack of alibi, found objects, etc, etc". It's your job now to challenge the evidence that I provided.

[Bored Wombat]

MODTRAN gives you less than this: http://www.physicsforums.com/showpost.php?p=1358505&postcount=2

Andre calculated this, and I also did the exercise myself. You get 0.77 K per doubling of CO2.
That's right. The 3°C is the climates response to the increase in radiative forcing due to a doubling of CO2, and once the new equilibrium is reached.
So even the 1.5 degree per doubling is not clear, unless you *assume* that current temperature increase is *entirely* due to human driven effects, and then after the fact you use this number to *prove* that it is human-caused.
You don't have to assume it. You can estimate it independently.
You can estimate it from paleocliamtic reconstructions, as the four papers to which I linked above.

You can estimate it from climatic observations:
An Observationally Based Estimate of the Climate Sensitivity (http://ams.allenpress.com/perlserv/?request=get-document&doi=10.1175%2F1520-0442(2002)015%3C3117%3AAOBEOT%3E2.0.CO%3B2&ct=1)

You can estimate it from radiation budget data:
The Climate Sensitivity and Its Components Diagnosed from Earth Radiation Budget Data (http://ams.allenpress.com/perlserv/?request=get-document&doi=10.1175%2FJCLI3611.1)

And, of course, you can estimate it from lots of GCMs.
Constraining climate forecasts: The role of prior assumptions (http://www.climateprediction.net/science/pubs/2004GL022241.pdf) (There are a great many papers that estimate climate sensitivity from GCMs of course.)
or functionally similar tools:
Probabilistic climate change projections using neural networks (http://www.cgd.ucar.edu/ccr/knutti/papers/knutti03cd.pdf)

This is often refined by Bayesian analysis:
Robust Bayesian Uncertainty Analysis of Climate System Properties Using Markov Chain Monte Carlo Methods (http://www.climate.unibe.ch/~stocker/papers/tomassini07jc1.pdf)

Estimated PDFs of climate system properties including natural and anthropogenic forcings (http://web.mit.edu/ceforest/www/ForestS06_GRL.pdf)

There have been a wide range of angle of attack on this one, so it is not circular.

[Andre]

That's right. The 3°C is the climates response to the increase in radiative forcing due to a doubling of CO2, and once the new equilibrium is reached.

Perhaps not. See this (http://www.physicsforums.com/showpost.php?p=1358505&postcount=2)

[Bored Wombat]

Perhaps not. See this (http://www.physicsforums.com/showpost.php?p=1358505&postcount=2)

You misunderstand.

The response of the whole climate system includes the effect of increased atmospheric water vapour, and decreased albedo from decreased ice cover, and a plethora of effects like that.

[Andre]

You misunderstand.

The response of the whole climate system includes the effect of increased atmospheric water vapour, and decreased albedo from decreased ice cover, and a plethora of effects like that.

No I not misunderstand. I know the tune, if you do the MODTRAN run with constant relative humidity then you get in the range of 1.2 - 1.4 degrees per doubling. However this creates energy since it disdains the energy required (2500 joule per gram) to evaporate the water required to keep the relative humidity constant in the first place. It can be calculated that the additional energy from doubling CO2 is insufficient to sustain that evaporation, meanwhile that energy required for evaporation is not available for heating. But this discussion is futile, it is still about motive and lack of alibi, whilst the innocence of CO2 has been proven.

[vanesch]

I know that it is coming from fossil fuel combustion, and the bulk of it is remaining in the atmosphere with the second largest lump dissolving in the oceans.
And I know that if you increase the partial pressure of a soluble gas, then more of it will dissolve in the oceans.


I also know that if you increase the temperature of the water, more CO2 will be released to the atmosphere. Currents can change. The relationship with the deep ocean can change. Plankton formation can change. Land coverage can change. Also, if you change the concentration in CO2 in the atmosphere, plankton can change, vegetation can change, chemistry can change.

If atmospheric CO2 is part of the global equivalent of a "buffer mixture" then there is a "set value" for its concentration, and any variation will be compensated by shifting reaction equilibria. If the set value of the mixture is changed, then the equilibria will shift in such a way as to vary towards the new set value, no matter whether or not there is a different source.

If one wants to demonstrate that a source is responsible for a level shift, then one has to demonstrate that all other sources and sinks in the cycle are not going to act as regulators, like a buffer mixture is in a simple chemistry experiment.

This is what I haven't seen in the arguments presented that are supposed to be a proof of the human origin of CO2 LEVEL in the atmosphere. It isn't sufficient to show that there is a source, you also have to demonstrate that all other systems coupled to it won't act as a regulator, and that it is not the regulator that has a different setting value.


That's not the usual meaning of source, but the oceanic efficiency as a sink is dropping. I can't speak for the terrestrial biosphere.

By what sort of mechanism?


Well, imagine the following. This is just a gedanken experiment. Imagine that there is a kind of plankton that grows strongly above a certain CO2 concentration, then dies off and drops to the ocean bottom. If that's the case, you can produce all the CO2 in the world, it will never get much higher than this threshold value, because beyond it, the plankton will grow exponentially and absorb all the excess CO2. But now, imagine for instance a virus that kills that plankton. Imagine that there is a second species of plankton, that acts the same, but at a higher threshold in CO2. Now that the low-threshold plankton is dead due to a pandemy, it is the second threshold that will be "set". During a certain period, the "set level" of CO2 will rise dramatically from the first to the second level. Then it will stabilize. It has nothing to do with sources and sinks. It is the regulated value by the big regulator which is plankton in this case which determines the CO2 level in the atmosphere, and you can pump as much extra CO2 in there, it won't change a thing.

As I said, that's just a gedanken experiment. But it illustrates what I mean with regulatory mechanisms which determine a certain concentration.

If you want to demonstrate that a simple in - out = result is effectively setting the level, then you have to demonstrate that there are no serious feedback mechanisms which tend to pull or push the result, but that it is just a passive balance of in - out.

So you need to know exactly the responses of all agents that could influence the in or out part as a function of the actual level in order to determine any feedback dynamics.

I haven't seen such a detailed analysis in the "proof of human caused CO2 level". Personally, I also think that it is human caused. But I wouldn't dare to make that a hard statement as many people do until all this was worked out. Fermat's last theorem was also believed to be correct, but it still took 400 years to prove it.


Okay, my case is that the oceans don't want anything. They'll outgass if the solubility for CO2 decreases, and otherwise dissolve some of any atmospheric increase and release some of any atmospheric decrease. This is how water behaves.



Yes, a pot of stationary water without anything. An ocean with currents, life in it, gradients of different kinds is totally different. You first have to understand exactly how it responds to changing CO2 levels, to changing temperature, to changing other parameters. The same (even harder) for land.


They are certainly both going on, and we know this not by looking at the graph, but because the physics is understood. CO2 is a greenhouse gas,


Physically, CO2 is a *weak* greenhouse gas in a stationary atmosphere (cfr MODTRAN), and it is even not clear how it behaves in a convective atmosphere or how it acts upon the much more important greenhouse gas which is water vapor, and which is entirely set by feedback mechanisms.


and it's solubility decreases with increasing water temperature at least around the sort of temperatures that the oceans are.


yes, again, in a simple pot of water. How about real oceans, and their life in it ?


No, I know from the fact that all the CO2 is coming from fossil fuel combustion, and that most of what is not remaining in the atmosphere is dissolving in the oceans, therefore the terrestrial biosphere is not setting the level of atmospheric CO2. It is largely set by an interaction between human activity and the oceans.


Isn't this circular, again ? You START with your assumption that the only source is fossil fuel combustion which is rising atmospheric concentration, then you say that oceans are only absorbing part of it (because the concentrations are rising) and then you conclude that hence the supplement is what oceans cannot absorb is what causes the rise, hence this is the cullprit.
Maybe. Or maybe if there wouldn't have been fossil fuel combustion, the oceans would have outgassed more (as they are heating up, for instance ?), and that would have made the CO2 levels also rise ...



Sorry, what proxy are we talking about here?


The O18 temperature proxy and the CO2 concentrations in the ice cores.


Where is it called an "undeniable proofs"? It is certainly true that a doubling of CO2 results in warming of over 1.5°C robustly throughout the last 420 million years. Is that what you mean by "drives" temperature?


Why don't you say that rising 1.5 degrees rising doubles CO2 concentration ?


Well, I don't think it is really an assumption, because we know where it comes from, and we know that it's concentration is 30% above what it normally peaks at during an interglacial, so we know well enough that this level is not due to some natural mechanism.


Uh. That's a weak argument. Who tells you that the dynamics is not changing (say, biological evolution, different land usage, changing ocean currents, solar activity, what ever...) ?

So now the argument "the CO2 levels are human-made" comes from "we didn't have those levels in the past" ??

I agree that all this is suggestive, but "I know that it is so" needs some more solid proof, don't you ?

In fact, it is easy to establish if atmospheric CO2 levels are human-caused or not. It is sufficient that humanity will decrease its fossil-fuel output, and this will happen anyway, because we will eventually (in one or two centuries) run out of them or don't need them anymore. When human fossil fuel combustion will stop, it will be sufficient to see whether atmospheric levels will decrease again with the same amount. Then (50 - 200 years from now) this point will be settled. So there is no scientific suspense: we will find out.


And I think it strange that we are looking for such a mechanism.
"We're putting 11Gt of Carbon into the atmosphere every year, but where is this 7Gt of carbon that is accumulating in the atmosphere every year coming from?" It doesn't seem to be that worthwhile a question to dwell on.


Yes, exactly like the guy on the shore who sees the tide rise, and thinks it is due to that other guy pooring water in the ocean... Of course, if it is a bath tub, he is right.

It is the very fact that you don't find that worthwhile a question to dwell on which worries me !!
That's exactly what Feynman's remark was about. You're not trying to prove yourself wrong.


But if you consider the paleoclimatic reconstructions, I think there is sufficient support for the surely obvious to convince most juries beyond all reasonable doubt.


Depends on the standards of the jury. Knowing something scientifically means that there is no room for doubt.

If you want to persuade me that there is a reasonable chance that this atmospheric CO2 might have something to do with human activities, then there's no problem. It sounds reasonable. If however, you say that you "know" that this is so and that should be the end of the discussion, then I want scientific proof, and the LOGIC of what is presented as such proof is flawed, because it doesn't lead to an impossibility of it being otherwise.


It's not the other way around. They move simultaneously for the most part.


Simultaneously with 600 years lag between the cause and the effect....

A correlation between A and B means: A causes B or B causes A or there is a common cause C which causes A and B.

A causes B was the first obvious option, until it became clear that A came later in time than B. So now it is B causes A causes B (because we really NEED A causes B). And why not C ? And why not B causes A ?

Because CO2 is a strong greenhouse gas. Why ? Physically it is a week greenhouse gas. No, it is a strong one with the feedback! Look at the paleodata where A causes B !


Do you have an example of this previous argument in the words of the IPCC that was erroneous?


I've been looking all afternoon, and I don't find it. :shy: Nevertheless, I was convinced that at a certain point it was stated that the correlation between the temperature and the CO2 was supposed to indicate that the CO2 clearly drove the temperature (before the 600 year lag was discovered). Now, maybe this was not the IPCC. I thought that it was, but I cannot find it, so I might be wrong. I DID see however the Vostok icecore data being used as an argument that CO2 drives temperature *somewhere*.


You don't need to prove the greenhouse effect, it is a result of well understood optics. It has been proven a century or so. The world would average a chilly -15°C without it.

The well-understood optics gives you 0.77 degrees per CO2 doubling.

[vanesch]

That's right. The 3°C is the climates response to the increase in radiative forcing due to a doubling of CO2, and once the new equilibrium is reached.

You don't have to assume it. You can estimate it independently.
You can estimate it from paleocliamtic reconstructions, as the four papers to which I linked above.

You can estimate it from climatic observations:
An Observationally Based Estimate of the Climate Sensitivity (http://ams.allenpress.com/perlserv/?request=get-document&doi=10.1175%2F1520-0442(2002)015%3C3117%3AAOBEOT%3E2.0.CO%3B2&ct=1)

You can estimate it from radiation budget data:
The Climate Sensitivity and Its Components Diagnosed from Earth Radiation Budget Data (http://ams.allenpress.com/perlserv/?request=get-document&doi=10.1175%2FJCLI3611.1)

And, of course, you can estimate it from lots of GCMs.
Constraining climate forecasts: The role of prior assumptions (http://www.climateprediction.net/science/pubs/2004GL022241.pdf) (There are a great many papers that estimate climate sensitivity from GCMs of course.)
or functionally similar tools:
Probabilistic climate change projections using neural networks (http://www.cgd.ucar.edu/ccr/knutti/papers/knutti03cd.pdf)

This is often refined by Bayesian analysis:
Robust Bayesian Uncertainty Analysis of Climate System Properties Using Markov Chain Monte Carlo Methods (http://www.climate.unibe.ch/~stocker/papers/tomassini07jc1.pdf)

Estimated PDFs of climate system properties including natural and anthropogenic forcings (http://web.mit.edu/ceforest/www/ForestS06_GRL.pdf)

There have been a wide range of angle of attack on this one, so it is not circular.


Do these papers analyse any cause-effect relationship, or do they estimate what is the correlation coefficient between the CO2 level and temperature rise, ASSUMING that it is the CO2 that is the cause, and the temperature the effect ?

In other words, in what way do they prove a causal relationship, and in what way are they estimating a correlation coefficient ?

[Bored Wombat]

And then I demonstrated that the fingerprint did not match, hence there is evidence that CO2 did not do the job, hence, it's all over, innocent, period! So what use is it to continue talking about "motive, an opportunity, a lack of alibi, found objects, etc, etc". It's your job now to challenge the evidence that I provided.

You are seriously claiming that the greenhouse effect isn't true because your remarkably trivial spreadsheets only look a little like like the remarkably complicated climate's response to forcing?

Because if that's what you're claiming, then I don't think that we need to go in to it.

I think that CO2 affects the temperature because it blocks earth heat more than it blocks sun heat. Therefore it does make it warmer. How much? I've cited about 10 papers in this thread, but there have been between 60 and 70 over the years that make an estimate. The answer is about 3°C per doubling. And that's been true throughout geological history too.

[Andre]

You are seriously claiming that the greenhouse effect isn't true because your remarkably trivial spreadsheets only look a little like like the remarkably complicated climate's response to forcing?

Because if that's what you're claiming, then I don't think that we need to go in to it.

I think that CO2 affects the temperature because it blocks earth heat more than it blocks sun heat. Therefore it does make it warmer. How much? I've cited about 10 papers in this thread, but there have been between 60 and 70 over the years that make an estimate. The answer is about 3°C per doubling. And that's been true throughout geological history too.

Better go over this thread a bit more carefully since you completely missed the point again.

[Bored Wombat]

Do these papers analyse any cause-effect relationship, or do they estimate what is the correlation coefficient between the CO2 level and temperature rise, ASSUMING that it is the CO2 that is the cause, and the temperature the effect ?
The majority of the work (but not the majority of these papers) is from GCMs, which of course analyse the cause effect relationship by modelling it.

The statistical and neural net papers look for constraints on the parameter climate sensitivity. I guess they could find a zero or negative one if there is not a causal relationship.

Needless to say, they don't.

and in what way are they estimating a correlation coefficient
They don't estimate a correlation coefficient.

[vanesch]

The majority of the work (but not the majority of these papers) is from GCMs, which of course analyse the cause effect relationship by modelling it.

The statistical and neural net papers look for constraints on the parameter climate sensitivity. I guess they could find a zero or negative one if there is not a causal relationship.

Needless to say, they don't.


They don't estimate a correlation coefficient.

I don't know if you see the difficulty to distinguish between both. In a dynamically coupled system, in fact, what is "cause" and what is "effect" is sometimes extremely difficult ; it can be hard to determine causal relationships without having experimental access and be able to change the cause at random and see if the effect is correlated. I have the impression, when I read those abstracts, that people take it for granted that the drive is the CO2, and then try to find what is the dynamical system that gives temperature. I don't see them try the opposite, for instance. I don't see them try to establish by how much CO2 could rise given a temperature change.

I don't see them take as a starting point "let us assume that CO2 doesn't affect temperature (and, say, temperature is driven by other factors, such as albedo change, ocean current change,...), and see where that leads us". No, they take as a starting point that there is a "radiative forcing", that its effect is temperature change, and then go on estimating how much it is, *starting from that hypothesis* that the main drive is radiative forcing. Then they find a value that can explain data. Fine, but that didn't prove the starting hypothesis.

Let me tell you again why all these things bother me. As I said, I'm a proponent of nuclear power, and it is of course an attractive discourse to say that we need nuclear power for reasons of AGW. However, if you make that link too strong, and AGW turns out not to be true, then this will backfire, and I think there are also *other* reasons than AGW to promote nuclear power. So before I want to link the advantages of nuclear power to AGW, I want to know whether the case for AGW is strong enough so that *no possibility exists that it will turn out, 20 years or 30 years from now, that it turns out not to be there*. Because, I don't know if the AGW crowd realizes this, we WILL eventually find out. It is not like a futile debate about, say, the interpretation of quantum theory or something, or string theory or whatever, where there will be always a way to wiggle out, or where there won't be any way to know for sure. No, with AGW, there is no *scientific suspense*: we will find out. We will have serious indications in 20 or 30 years and we will know for sure in 50 - 200 years. So before wanting to link the fate of nuclear power to the fate of AGW, I wanted to find out how strong the AGW case is, so I started playing the devil's advocate. I said: I'm going to read the AGW material (mainly from the IPCC) and I'm going to try to find loopholes in it. Given that I'm not a climate scientist (but on the other hand, I'm a physicist and I think I know enough about stuff such as radiation transport and so on to know the basics), I shouldn't be able to find ANY LOOPHOLE in the argument.

And that's where my disappointment came from: there's no logical case at all ! It is just a pile of suggestive evidence, and a lot of logical errors ! Suggestive evidence, to me, is observations which are more or less in agreement with what one would expect if one willingly takes on as hypothesis the statement to be proved. Logical proof to me is a set of contradictions one finds when one takes on most if not all thinkable hypotheses that contradict the to be proven hypothesis: it is falsifying the reasonable alternatives.

Now, a bad sign to me was that arguments used as "smoking gun" only 10 - 15 years ago as proof for AGW had to be reviewed in such a way that, to me (playing the devil's advocate), undid it of about all the smoke they displayed back then. That doesn't mean that they aren't still suggestive, but they've LOST their convincing power they had back then.

- You may read into the "hockey stick" plots whatever you want, you cannot deny that the display of the 2001 hockey stick is far far more convincing than the different 2007 hockey sticks without the current instrumental data glued on them.

- The 600 year lag between temperature rise and CO2 rise spoils a bit the evident "cause-effect" relationship that CO2 causes a temperature rise

Also, the arguments put forward to prove the two main theses of AGW, namely that the atmospheric CO2 content is fossil-fuel driven and that CO2 is a strong greenhouse gas seem to fail. I didn't say that this isn't true, I'm saying that the *arguments put forward* don't conclusively lead to the conclusion they want to demonstrate (like in mathematics, where there's a hole in the proof).

The 3 points: O2 decrease correlated with CO2 increase, isotopic composition of atmospheric CO2, and correlation between CO2 increase and fossil fuel exhaust, while of course suggestive, do not lead to the LOGICAL conclusion that the CO2 LEVEL is determined by the fossil fuel exhaust, given that the atmosphere is coupled to large carbon reservoirs (ocean, land mass) which have a dynamical relation with temperature, and with the CO2 level.
I jumped up when I read those arguments in the IPCC report (the physical basis, 4AR), because this was the first thing that came to my mind. I didn't see that point addressed at all.
Again, these 3 points are suggestive evidence. If you take as a starting point, the thing you want to prove namely that "atmospheric CO2 is rising because of fossil fuel combustion"(because you are somehow a priori convinced that this is true), then of course the 3 arguments are "in resonance" with what you think already: "Yeah, given that we are already sure that atmospheric CO2 is human driven, it's no wonder that CO2 increases with fossil fuel combustion, and that consumes oxygen, and then see, it was the same CO2 that we find in the atmosphere as the one that was consumed". That's suggestive evidence indeed. It is compatible with the suspected cause.
But it doesn't PROVE it. And to show you that it doesn't prove it, I simply have to find a counter example where the same LOGIC is used (show you that the observed increase of A is correlated with the output of source B, show you that the isotopic composition of A corresponds to that of source B, show you that some other quantity diminishes with B) and nevertheless the inferred causal relationship is NOT true in this case. That was the heavy water and the shore.

Again, this doesn't say anything about what I think about where the CO2 comes from. I also think it is sensible to think it comes from fossil fuel combustion. But it is not because I also think that Fermat's last theorem is true, that I think that your proof of it is correct!

This is so an elementary logical error that I found it extremely worrisome that it wasn't obviously addressed, and what I found even more so, was Bored Wombat's reaction which I'm afraid illustrates this: yeah, ok, with your nitpicking you found maybe a hypothetical logical error, but then the proof wasn't needed in the first place because we knew already of course that it was fossil fuel output that set the CO2 level. I don't even see why we should bother...


This illustrates the cavalier attitude towards scientific inquiry, and not Bored Wombat's, but the whole AGW crowd I am afraid.

If this is really true, then you don't present evidence as logical proof with a logical flaw in it. You simply say that you have to take it as an article of faith that CO2 levels are "of course" fossil fuel driven, and that if you take on that article of faith, then there is circumstantial evidence that comforts that idea.

The next point is: "CO2 is a strong greenhouse gas". I haven't seen any proof of that either, that doesn't work in the same circumstantial way. Most arguments presented follow the same kind of argument: "take it as an article of faith that CO2 is a strong greenhouse gas", and then, starting from that hypothesis, we can explain this and that. And if one asks then if there's ANOTHER way of explaining this or that, then the answer is: not needed, we KNOW that CO2 is a strong greenhouse gas. Ultimately, the argument is: we know the OPTICS OF CO2, it tells us it is a greenhouse gas. Yes, but the optics tells you it is a WEAK greenhouse gas.

In the papers you cite, I have the impression that one doesn't try to PROVE that it is the CO2 that was the cause and one doesn't try to prove that it is the CO2 that is working as a greenhouse gas. It is simply taken as a hypothesis (especially all the statistical estimators! I've done neural network simulation also, in a totally different context as black box models for microwave electronic components when I was working with HP: I can tell you that no neural network is ever taken seriously as a cause-effect dynamical model: it is always a black box).

So when digging into all this, I was appalled at the lack of criticism towards the basic hypotheses on which the whole AGW theory is built. It is as if one has to take them as articles of faith, and then we get a huge pile of suggestive evidence which "makes sense - more or less" when one has taken them already as truth. This HAS some value of course. But it is far from establishing the original hypotheses.

Also, what is worrisome, even more so, is the lack of critical inquiry in those pieces of evidence that don't seem to fit perfectly into the puzzle.

So although there is of course suggestive evidence (if you read it with the "right" mindset), I am far from convinced that one has an "air-tight case". I wouldn't want to convict anyone on such shaky evidence alone, and I'm amazed that this could even be there. After looking into all this, I'm less inclined to promote, say, nuclear power on such a shaky basis, because I take the possibility very very real that all this may turn out simply not to be true, and that it will seriously backfire if ever that's the case.

On the other hand, I don't find much evidence either that AGW isn't true, and in as much that it might be catastrophic, even if it has a 30% chance of being there, one should consider fighting it (the expected damage is then one third of the estimated AGW damage, which is still very consequential). After all, there IS a lot of suggestive evidence. There is a lot of data that doesn't contradict the hypothesis, and that's of course also a way to "prove" things - on the condition of being honest ! In that case, one has to *try to find - even a single case - evidence which might *contradict* the working hypothesis. In as much as one *really tries* to falsify one's working hypothesis, after sufficient time, and if EACH TIME the falsification didn't work, this also builds confidence in the working hypothesis. But there's a danger here. There is the danger that one selects only those cases where the falsification doesn't work, and *one might be inclined to neglect those cases where falsification might work*. That's what a lawyer does, on purpose. And that's the trap Feynman warned against.

And the reaction I see to small indications that there might be some details that "don't fit" scare me. The point Andre brought up should worry climate scientists. What Andre did was taking the cavalier "explanation and proof" that the lagging CO2 in the paleodata act as a positive feedback mechanism, literally. He set up a very simple model with a simple positive feedback - as one does in system dynamics 101 - and looked at the result. But he didn't need to do that: simple positive feedback is known to lead to multistability. So if the explanation was indeed so simple and "evident" as given by the AGW crowd to make the lagging CO2 nevertheless "causal", then this multistability should explain most of the data. And in fact, it does explain part of the data, but it is in contradiction with certain passages such as Andre indicates. And in dynamics, the devil is in the details, and Andre points out correctly that you cannot have that kind of behaviour in a multistable system with positive feedback. Of course his model is way too simple. That's not the point. But if the explanation were so easy (evident proof of the CO2 as causal agent), then the model would be easy to. So this is more complicated.
The comment of "yes, but in reality it is more complicated" is of course acceptable, ON THE CONDITION THAT IT IS UNDERSTOOD.

So my question is: has there been a dynamical model using exactly the proposed causal relationships, which PREDICTS CORRECTLY exactly the passage Andre illustrated ? Has one identified in that passage exactly what was then the cause of the LOWERING of the temperature when CO2 was rising slowly ? Because this is going to be difficult in a positive-feedback model, so this is exactly the kind of relevant detail which needs to be adressed. THIS is the kind of falsification exercise which is worthwhile: we seem to have a piece of data which CONTRADICTS at first sight the working hypothesis, this is an ideal case to test falsification on. Has this been done ?

[vanesch]

Another point which I don't find addressed in the argument that CO2 is a *strong* greenhouse gas (that is supposed to explain more than 33 K of greenhouse effect), is the difference between its effect on the earth and on Mars.

Mars has about 7 mbar of partial (and in fact total) pressure of CO2, while the earth has less of it (about 0.4 mbar, no ?). So the *purely optical greenhouse effect* should be much stronger on Mars than on the earth. Actually, there are two main differences: the total pressure of the atmosphere is totally different, and as such, we can expect maybe a different Doppler broadening. Also, the temperatures are lower on Mars, so the thermal spectrum is shifted, and hence the relative intensities will be different. But not much so. The greenhouse effect on Mars is of the order of 6 K for about 15 times more CO2 than on earth. A 5 times smaller effect for a 15 times higher concentration is two orders of magnitude difference.

Of course, on Mars there are no feedback effects, but there is also no water vapor.

I'm not claiming anything here. I'm not saying that the small greenhouse effect for the large quantity falsifies as such the claim of a large greenhouse effect on earth. But it is an evident test case and I find it extremely strange that this point isn't addressed. The data are much clearer than paleodata: there are two orders of magnitude to be explained away. It is funny that this is not even found worthy of being addressed.

BTW, this article http://www.nature.com/nature/journal/v446/n7136/abs/nature05718.html is interesting, because it points to albedo changes explaining most of the temperature variations on Mars. The funny thing is that this effect was used to counter a AGW sceptics comment that recently, Mars was also warming, which they pointed then to a common solar irradiance effect.
True, but if albedo variations have such an important effect on global temperature on Mars, has this been studied on earth ?

[Andre]

The greenhouse effect on Mars is of the order of 6 K for about 15 times more CO2 than on earth.

According to this fact sheet (http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html) both the average temperature and the blackbody temperature are 210K.

On the other hand there is Venus, which has a "greenhouse" effect of 506 degrees suggesting some 20 degrees order of magnitude per doubling CO2. But there is one big difference with Earth, there is not a lot of convection (http://www.agu.org/pubs/crossref/2002/2001JE001501.shtml) in the atmosphere of Venus, which together with the water cycle regulates the temperature on Earth working as an Air conditioner.

[Bored Wombat]

Another point which I don't find addressed in the argument that CO2 is a *strong* greenhouse gas (that is supposed to explain more than 33 K of greenhouse effect), is the difference between its effect on the earth and on Mars.

I don't think that that can be right. 33K is the entire greenhouse effect.

Although CO2 is responsible for most of the enhanced greenhouse effect, being that anthropogenic part of it, it is only responsible for 9% or 26% of the total greenhouse effect, depending on whether or not you include overlap with other greenhouse gasses.

So the most I think you could reasonably claim is about 9K. 3K would also be reasonable, if it is defined as the amount less of the warming that there would be if CO2 were removed entirely. Assuming radiative forcing translates linearly into temperature ... Which might be close for small changes in radiative forcing. (A straight line approximates the T4 curve for small sections of it.)

Who is claiming 33K?

Of course, on Mars there are no feedback effects, but there is also no water vapor.

There's wind. Which is stronger overall if there's more radiative forcing. That's a feedback because it stirs up dust with affects the Albedo.

BTW, this article http://www.nature.com/nature/journal/v446/n7136/abs/nature05718.html is interesting, because it points to albedo changes explaining most of the temperature variations on Mars. The funny thing is that this effect was used to counter a AGW sceptics comment that recently, Mars was also warming, which they pointed then to a common solar irradiance effect.
True, but if albedo variations have such an important effect on global temperature on Mars, has this been studied on earth ?
Of course. Albedo is an important aspect of climate modelling.

I recall the original paper talked about albedo driving the climate change on Mars, and the denilaists ignoring that while flooding the chatshows and opinion pieces with the view that it was caused by variation in solar irradiance. Despite the lack of positive trend in solar irradiance over the past 30 years.

[vanesch]

I don't think that that can be right. 33K is the entire greenhouse effect.


Yes, it is the difference between the thermal equilibrium temperature of the grey body at the actual solar irradiance and the actual temperature.


Although CO2 is responsible for most of the enhanced greenhouse effect, being that anthropogenic part of it, it is only responsible for 9% or 26% of the total greenhouse effect, depending on whether or not you include overlap with other greenhouse gasses.

So the most I think you could reasonably claim is about 9K.
3K would also be reasonable, if it is defined as the amount less of the warming that there would be if CO2 were removed entirely. Assuming radiative forcing translates linearly into temperature ... Which might be close for small changes in radiative forcing. (A straight line approximates the T4 curve for small sections of it.)

Who is claiming 33K?


And who said that the world would be a chilly snowball of about -15 C without (what I presume the CO2 greenhouse effect - as it was used to show that CO2 was a strong greenhouse gas) ?


You don't need to prove the greenhouse effect, it is a result of well understood optics. It has been proven a century or so. The world would average a chilly -15°C without it.


The whole discussion turns around *how much* an increase in CO2 affects the greenhouse effect, in other words, is CO2 a strong or a weak greenhouse gas. The bare bone optics tells us it is 0.77 K for a doubling from 280 ppm to 560 ppm, which means it is rather weak. In order to change that into 1.5 - 6 K, one needs to show me where the trick is. I don't say that this is impossible because there can be feedback effects. Those can be positive, negative, or irrelevant. But I would like to see - and with all the "scientific certainty claims" there MUST be - an almost airtight logical reasoning that proves us that a doubling of CO2 brings us within a 1.5 - 6 K range, *so that it could eventually be recognized as an important source of heating*, and I haven't seen that. What I have seen are a lot of studies that *take it for granted that the observed heating is due to CO2* and then go on estimating what must be the feedback effect SO THAT the heating can be explained by the CO2 change. But that's of course no proof that the CO2 was the principal cause in the first place. Once they've estimated how much CO2 must heat, in order to explain the heating, then, low and behold, the CO2 explains exactly the amount of heating! Now, because that needed heating is much larger than the optics tells us, that is then seen as a *proof* that there must be positive feedback effects, which have to explain why CO2 is heating more than it is purely physically supposed to do. And if one then asks how does one know that the heating didn't have another cause, then the answer is, because CO2 can explain it, with the positive feedback effects! When I make that objection, I get the answer that it is "known". But where does the proof that CO2 is the *source* of the heating come from, that doesn't already ASSUME that it is the source ?

In this respect, Mars is an interesting "reality check" on the bare bones effect of CO2: with 15 times more CO2 in the atmosphere, its "optical" pure-CO2 greenhouse effect is tiny. The main difference is that the "feedback effects" are switched off, or are different. Don't forget that this is nevertheless the "drive" of the current AGW theory. What we see on Mars is that the CO2 doesn't play a role of significance in any changes of temperature: albedo is then a strong forcing agent.

And then the question is: imagine that those feedback effects really exist. That means, imagine that a tiny drive (such as the all-optical CO2 drive, but also a change in ocean currents, or a small change in albedo - think use of coal and black particles which is correlated of course with CO2 exhaust - or whatever) can and will indeed be amplified to large proportions (and hence, in the linear domain, that small temperature decreases can also be amplified into large coolings). That would then mean 2 things: 1) big instabilities and 2) *any* small initial temperature forcing would be amplified.

I may of course have it all backwards, and maybe you can reassure me with a logical proof that CO2 IS a strong greenhouse gas, and that I can hope that AGW is here to stay (indeed, my greatest fear is that it might not be there as strongly as one claims). So what's the logical argument that leads us to conclude, without hesitation, that CO2 cannot be anything else but a strong greenhouse gas ?

Again, don't understand me wrong. I'm more kind of attacking the logic of the whole thing than discussing whether or not AGW is there. It's more like the mathematician who is verifying the proof of a theorem and finds logical leaps that don't seem to be sound, than discussing of whether the theorem is true. It's more about the scientific method than any actual climate science.

[Andre]

I would not bet my money on the 33 degrees (actually 34.5 degrees) difference between average surface temperature and black/gray body temperature being greenhouse effect, because it's convection effect instead (Chilingar et al 2008). The difference would probably be even more if it weren't for greenhouse gasses.

Recheck these vertical temperature profiles registered at various times of the day, giving that away:

http://mtp.jpl.nasa.gov/missions/texaqs/austin_poster/Image11.gif

Caption:

The figure to the right uses PNNL radiosonde data to show the diurnal variation of temperature profiles for August 31, 2000, at La Marque. The UTC launch times were 0501 (pink), 0758 (red), 1106 (light blue), 1401 (green), 1700 (white), 2000 (yellow) and 2300 (grey). It is clear that ground-level nighttime inversion vanishes between 1401 and 1700 UTC, and reappears after 2300 UTC. ...

Look how little daily cycle effect there is in the atmosphere above 2000 feet. Let's see why.

The air gets heated at day time due to a combination of

1: warm air convection from the surface to higher levels,
2: latent heat exchange, evaporating at the surface takes heat away and condensing at higher levels releases the heat again, while forming clouds
3: greenhouse effect

As we can see in the diagram at night time the higher layers cool again due to:

3: greenhouse effect, radiating energy out to space

...since there is no heat exchange mechanism with the surface, and there is no such thing as downward convection. It's one way only, up.

Now, suppose that there were no greenhouse gasses in the atmosphere, then there would NOT be cooling at night in the higher levels, actually perhaps also in the lower levels as we may assume that a part of the cooling there, is due to more effective back radiation to earth and Earth radiating it out this on other IR frequencies in better emission windows. That would also not go when there were no greenhouse gasses, and what is left then, would only be conduction of the lowest few meters perhaps, which is highly ineffective

So the next day, with the atmosphere still warm, the temperatures could be driven even higher and in the end the higher level lapse rate would theoretically equal that of the warmest day all the time, year around. If it wasn't for the cooling out radiating effect of greenhouse gasses the Earth would likely really be hot.

Also, if we look at all the heat exchange processes at day and night, we see that the greenhouse effects at day and night oppose each other, they may not cancel each other out but the question can be asked if greenhouse effect heats or cools

There are also non-diurnal processes causing warming of the atmosphere like heat advection (http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/af/adv/adv.rxml). This happens for instance when cold and warm air masses collide, then the warmer air is forced over the colder air due to the density difference hence also transporting energy from the earth surface into the atmosphere and heating it above gray body temperature

[vanesch]

Now, suppose that there were no greenhouse gasses in the atmosphere, then there would NOT be cooling at night in the higher levels, actually perhaps also in the lower levels as we may assume that a part of the cooling there, is due to more effective back radiation to earth and Earth radiating it out this on other IR frequencies in better emission windows. That would also not go when there were no greenhouse gasses, and what is left then would only be conduction of the lowest few meters perhaps, which is highly ineffective

So the next day, with the atmosphere still warm, the temperatures could be driven even higher and in the end the higher level lapse rate would theoretically equal that of the warmest day all the time, year around. If it wasn't for the cooling out radiating effect of greenhouse gasses the Earth would likely really be hot.


I don't see how this can work. If there are strictly no greenhouse gasses in the atmosphere, then the atmosphere can almost not radiate out any of its internal thermal energy (almost, because nothing is totally decoupled from the EM field). That means that the radiative balance earth-surface / outer space / sun is as if there were no atmosphere. The earth surface would essentially act as a grey body radiator, directly into space, and receive visible light directly from the sun. The atmosphere would be entirely transparant.

However, as you point out, what still works is heating of the lower air by conduction, and of course convection will also play a role, until the upper layers get at the hottest possible temperatures of the earth surface, at which point, convection will stop, because we get a well-ordered atmosphere, the higher you go, the hotter it gets. At that point the convection heat pump stops, and we would just get the lower layers which follow more or less the surface temperature, and remain colder and hence heavier than the top layers: they would simply add some effective thermal capacity to the earth surface.

And the surface would settle at its black (or grey) body temperature because the only heat loss mechanism would now be radiation, straight through the atmosphere.

Of course, in as much as the atmosphere is not totally decoupled, and does radiate a bit of thermal energy away, one should find out whether the radiated BB radiation from the atmosphere (partly in space, and partly back to earth) does anything. But I don't see how convection could HEAT the earth surface.

[Andre]

And the surface would settle at its black (or grey) body temperature because the only heat loss mechanism would now be radiation, straight through the atmosphere.


Really? but isn't this ignoring the daily effects. After all, at the equator at noon, each square meter is getting the full 1367 watt, not the average, that's good for the full 360K (albedo 0.3) and that would be the temperature base (minus lapse rate) of the local atmosphere above the transient layer in steady state? That is to say when there is no more convection after completing the heating up of the atmosphere.

So after dawn the surface would heat up quickly because in the steady state there is no more convection to take the heat away, but how fast would the surface cool at night with the hot air above? Wouldn't there be asymmetrical heating and cooling, having a different average?

And what would be the average temperature now at 1.80 meters? or whatever the height of the official meteorologic observation stations may be. After all we are talking about the measured 'surface temperatures' as the air temperature at such and such height and not the actual temperature of the ground surface in the 33 degrees difference now.

[vanesch]

So after dawn the surface would heat up quickly because in the steady state there is no more convection to take the heat away,


But there would still be an effective thermal capacity, smoothing out temperature variations.


but how fast would the surface cool at night with the hot air above? Wouldn't there be asymmetrical heating and cooling, having a different average?


The hot air not having any greenhouse gasses (and hence not radiating any IR), it wouldn't affect (much, there would be a little bit of radiation of course, and there would be a bit of conduction even) the surface temperature. Let us not forget that we are in an idealized gedanken experiment in which there is almost no greenhouse gas, and hence almost no thermal radiation emitted from the gas layers.


And what would be the average temperature now at 1.80 meters? or whatever the height of the official meteorologic observation stations may be. After all we are talking about the measured 'surface temperatures' as the air temperature at such and such height and not the actual temperature of the ground surface in the 33 degrees difference now.

Well, as thermal conduction is not 0 (there is still thermal conduction in an ideal gas), there would be a thermal gradient which goes from the ground temperature to the "maximum temperature" at a certain height, and this gradient would be constrained by the threshold for setting off convection. So this fixes a certain height over which the temperature will vary (with some lag and everything) from the surface temperature to the "hot air" temperature. And 1.8 m will see a bit of that influence (or a lot, if that distance is only 5 meters - no idea).


In fact, the situation is a little bit similar (but then downward, not upward) with the ocean, and the cold lower layers in the deep ocean.

[Andre]

And 1.8 m will see a bit of that influence (or a lot, if that distance is only 5 meters - no idea).


In this example (http://www.bom.gov.au/info/ftweather/page_16.shtml) about 7 degrees:

http://www.bom.gov.au/info/ftweather/images/windy_night.gif

But that's including the radiative cooling of the lowermost atmosphere to the Earth surface, which is absent in the null hypothesis

Anyway, you should write all that critique to Chilligar et al 2008 in the cooling thread.

[Bored Wombat]

The whole discussion turns around *how much* an increase in CO2 affects the greenhouse effect, in other words, is CO2 a strong or a weak greenhouse gas. The bare bone optics tells us it is 0.77 K for a doubling from 280 ppm to 560 ppm, which means it is rather weak. In order to change that into 1.5 - 6 K, one needs to show me where the trick is. I don't say that this is impossible because there can be feedback effects. Those can be positive, negative, or irrelevant. But I would like to see - and with all the "scientific certainty claims" there MUST be - an almost airtight logical reasoning that proves us that a doubling of CO2 brings us within a 1.5 - 6 K range, *so that it could eventually be recognized as an important source of heating*, and I haven't seen that.
Well, I've pointed you to a few papers that estimate this very parameter.

You may or may nor recall the relevant part of the recent IPCC report (Section 6 of chapter 9). It cites about 20 papers, that address this same parameter. So if you are interested in understanding the ways in which extimates of climate sensitivity and what independent estimates that there are, then you're lucky because there's certainly not a paucity of studies on this aspect.

What I have seen are a lot of studies that *take it for granted that the observed heating is due to CO2* and then go on estimating what must be the feedback effect SO THAT the heating can be explained by the CO2 change.

I haven't seen any studies like that. Do you have citations for a handful or so of them? (Or links to the papers)?

In this respect, Mars is an interesting "reality check" on the bare bones effect of CO2: with 15 times more CO2 in the atmosphere, its "optical" pure-CO2 greenhouse effect is tiny. The main difference is that the "feedback effects" are switched off, or are different. Don't forget that this is nevertheless the "drive" of the current AGW theory. What we see on Mars is that the CO2 doesn't play a role of significance in any changes of temperature: albedo is then a strong forcing agent.
No, Mars has no combustion of fossil fuels, no oceans and no biosphere. So the CO2 concentration will be dead constant, yielding no change in temperature.

And then the question is: imagine that those feedback effects really exist. That means, imagine that a tiny drive (such as the all-optical CO2 drive, but also a change in ocean currents, or a small change in albedo - think use of coal and black particles which is correlated of course with CO2 exhaust - or whatever) can and will indeed be amplified to large proportions (and hence, in the linear domain, that small temperature decreases can also be amplified into large coolings). That would then mean 2 things: 1) big instabilities and 2) *any* small initial temperature forcing would be amplified.
The main mechanisms are water vapour, ice albedo, and in the longer term oceanic outgassing. Yes, it affects any change in radiative forcing.

I may of course have it all backwards, and maybe you can reassure me with a logical proof that CO2 IS a strong greenhouse gas, and that I can hope that AGW is here to stay (indeed, my greatest fear is that it might not be there as strongly as one claims).
We need to get a couple of things straight. 150,000 people per year are dying of global warming, and a great many more are suffering serious illness. Ecologists are estimating from range changes that we are looking down the barrel of 35% of species committed to extinction by 2050. Conservative estimates of cost are an ongoing 5% of world GDP. Realistic ones are 20%. If you care about the lives of people or the world economy or the world biosphere, then your fear should be that it is as strong as median estimates.

But there's a significant possibility that it might be around 6K per doubling, and if that doesn't have you shitting yourself you're not understanding the consequences.

So what's the logical argument that leads us to conclude, without hesitation, that CO2 cannot be anything else but a strong greenhouse gas ?
I'm not really familiar with these terms "strong" and "weak" greenhouse gas. I presume these are defined in terms of increase in radiative forcing per doubling of concentration?

CO2 is about 3.7 W/m2 for a doubling. If the line between "strong" and "weak" is more than that, then it is weak. If it's less, then it is strong. If you want to reduce it to a one bit step function.

Again, don't understand me wrong. I'm more kind of attacking the logic of the whole thing than discussing whether or not AGW is there. It's more like the mathematician who is verifying the proof of a theorem and finds logical leaps that don't seem to be sound, than discussing of whether the theorem is true. It's more about the scientific method than any actual climate science.

Proofs in Mathematics are very different from ones in any applied science. Different theories of gravitation, and different ways to unify it with other forces is under constant and prolific investigation. But if you drop a carton of eggs, it will fall to the ground.

Climate sensitivity is probably about 3.

[Andre]

Well, I've pointed you to a few papers that estimate this very parameter.

The netiquette would be that you quote or at least point to the specific sections where this occurs, so that the method of estimating is clear and can be evaluated. You can't expect from a busy scientist like Vanesch to wade through the deluge of papers. Just make your case in detail within the thread.

No, Mars has no combustion of fossil fuels, no oceans and no biosphere. So the CO2 concentration will be dead constant, yielding no change in temperature.

I would expect from any climate alarmist to understand the basic idea / hypothesis of greenhouse effect being the difference in the theoretical black / gray body temperature and the actual atmospheric temperature at the surface. The data are ambiguous about any difference between the two, despite the much higher concentration of CO2 compared to Earth. No need for fossil fuels, oceans etc.

We need to get a couple of things straight. 150,000 people per year are dying of global warming, and a great many more are suffering serious illness.

Would you care to substantiate that and also demonstrate that this is caused by the increase of CO2 and also how this could be mitigated / prevented if we put our own economy under great strain to get a tiny reduction in CO2 production?

Ecologists are estimating from range changes that we are looking down the barrel of 35% of species committed to extinction by 2050.

That's a study of several years ago. Could you point to a list of the, no doubt hundreds of species that went extinct since then, to match that number and also demonstrate that those extinctions are caused by higher temperatures due to increased concentrations of CO2?

[vanesch]

Well, I've pointed you to a few papers that estimate this very parameter.
You may or may nor recall the relevant part of the recent IPCC report (Section 6 of chapter 9). It cites about 20 papers, that address this same parameter. So if you are interested in understanding the ways in which extimates of climate sensitivity and what independent estimates that there are, then you're lucky because there's certainly not a paucity of studies on this aspect.


I will have a look at those again, in as much as they are available. But to get this straight, what I'm looking for are papers that demonstrate logically by falsifying all other possibilities that the source of heating is due to CO2. As such, they must start with all reasonable hypotheses where CO2 is NOT a serious source of the warming, but that something unknown is, and arrive at an undeniable conclusion that this leads to a contradiction with known laws or observations. I must indeed have overlooked the 20 something papers that do this. I'll look again.


No, Mars has no combustion of fossil fuels, no oceans and no biosphere. So the CO2 concentration will be dead constant, yielding no change in temperature.


I must have expressed myself badly. The *total* greenhouse effect on Mars is almost neglegible. But of course there is also no variation of it. The effect of albedo is of the same order of magnitude or bigger than the *total* greenhouse effect.


The main mechanisms are water vapour, ice albedo, and in the longer term oceanic outgassing. Yes, it affects any change in radiative forcing.


There are myriads of other possibilities that could change the surface temperature: changing ocean currents, ocean convection, changing wind patterns, changing cloud formation, changing precipitation, convection and I don't know what. All these mechanisms and probably many more can change the surface temperature by re-distributing the thermal energy, by changing the average temperature at equal radiant flux, and eventually by changing the outward radiant flux. The way thermal energy is re-distributed over the surface of the earth can have an important effect. It is only after having demonstrated that all these effects are NOT the main source of the observed temperature variations that one could eventually, by elimination and falsification of all alternatives, arrive at pointing at CO2. I haven't seen that, but I take it that it has been conclusively done - that's what I'm in fact asking for. It is only from that point on that it starts to be reasonable to suspect a stronger heating by CO2 than given by its optical effect.


We need to get a couple of things straight. 150,000 people per year are dying of global warming, and a great many more are suffering serious illness. Ecologists are estimating from range changes that we are looking down the barrel of 35% of species committed to extinction by 2050. Conservative estimates of cost are an ongoing 5% of world GDP. Realistic ones are 20%. If you care about the lives of people or the world economy or the world biosphere, then your fear should be that it is as strong as median estimates.


Howdy ! Now we aren't even sure about the temperature predictions of global warming, we can even give estimations of the number of victims. Aren't we pushing things a bit here ?

But as I told you, my main fear about the possibility of global warming not being true (or at least, *dramatic* AGW not being true) is that it would backfire on nuclear power. (It would also seriously backfire on all of science. All of science would have lost entirely its credibility, due to the bet of the AGW people to take suggestive evidence as final proof, and to fight by all means any critical analysis - hence the denigration of the "AGW deniers" or the "AGW sceptics"... the "non-believers" in other words. But that's another point) After all - and that's why I like AGW so much - this is the biggest joke that environmentalists ever played on themselves: if it is true, their opposition to nuclear power for more than 40 years is then mainly responsible for the biggest ecological crisis in recent history, and that is a joke that I find terribly funny (I am entitled to my strange sense of humor, no ?). It would honestly annoy me if it turned out not to be true so that we can replace again nuclear power stations by coal-fired plants, and that I cannot have my good laugh anymore. So it is that fear that drives me to want to find out for real if the possibility exists that AGW might finally not be so dramatic, because I want to prepare myself for a big deception. It is also the exceptional quality of environmentalists as fearmongers (which they used against nuclear power) and their wholehearted embracing of AGW which makes me suspicious: if the quality of the inquiry for AGW is of the same nature as the quality of their inquiry into nuclear affairs, then that could tell a lot about the factual truth of AGW.

The estimates of 150 000 people dying because of global warming (I really really wonder where that comes from, but never mind - does this include all the people who also enjoy the better weather ?) is insignificant compared to what we accept in any case as a reasonable risk: car traffic kills 1.2 million people a year and we use it to go on a holiday. So this is a minor issue. I hope you can do better than that ! I want more drama ! :biggrin:

However, you seem to forget that the atrocity of the crime is not an argument of guilt for the accused. It is not because the crime is terrible, that the accused is more likely to be guilty.


But there's a significant possibility that it might be around 6K per doubling, and if that doesn't have you shitting yourself you're not understanding the consequences.


I will be dead by the time that it manifests itself, so for me this remains a purely academic discussion in any case.


I'm not really familiar with these terms "strong" and "weak" greenhouse gas. I presume these are defined in terms of increase in radiative forcing per doubling of concentration?


It's of course not a technical definition. Take it that a weak greenhouse gas is one that doesn't matter much (that isn't any source of *dramatic* heating). I consider 0.77 K per doubling not dramatic. It wouldn't, in that case, be the principal drive behind global temperature changes.

A strong greenhouse gas is one that matters. One that becomes by far the main source of temperature change. As I told you - but apparently I must have overlooked them - I've never seen a conclusive proof that CO2 is the principal drive in global temperature change. Nevertheless, that's claimed as being *scientifically certain*. It is strange to claim that it is scientifically certain, but not to provide an air-tight proof.


CO2 is about 3.7 W/m2 for a doubling. If the line between "strong" and "weak" is more than that, then it is weak. If it's less, then it is strong. If you want to reduce it to a one bit step function.


Yes, MODTRAN gives me about that. For a change from 280 ppm to 560 ppm, constant water vapor pressure and tropical atmosphere, I find a change from 289.2W to 286W per square meter. This corresponds to a ground temperature change of 0.9 K.
For the standard 1976 US atmosphere, the same change brings me from 260.0 to 257.2 W per square meter, so here it is 2.8 W. Which corresponds to a ground temperature change of 0.8 K.

Given that a rise of 0.8 or 0.9 K isn't dramatic and that we can expect about a doubling of the CO2 content in the atmosphere in the 21st century, I hence classify CO2 as a weak greenhouse gas.

This means, if I understand well, that a doubling of CO2 is equivalent to any other physical mechanism that would change the global temperature by a bit less than 1 K, like for instance a change in albedo of 1%. So to demonstrate that CO2 IS the main driving factor, we first must have conclusively shown that there cannot exist any other mechanism that could influence global temperature for about 1K. One has to be able to control ALL other thinkable mechanisms to much better than 1K and demonstrate that they don't play a role. Only in that case can one conclude that the initial drive was 1K, and that there are then feedback mechanisms which must turn this into 1.5K or even 6 K. Only then it is demonstrated.

If you want to include water vapor feedback for instance, which adds of course a greenhouse gas, and which is one of those potential positive feedback parameters (anything else equal, like cloud formation), then that feedback is just as well valid for, say, albedo change, or any other process that changes global temperature with 1K (at constant water vapor). In general, anything that amplifies the effect of the radiative forcing of CO2, will also amplify the effect of anything else that has the same effect as that radiative forcing.

Let us take albedo just again as a thought experiment. We get about a 1 K increase if the albedo changes by 1% (because solar flux is about 350 W/m2 and hence the radiative forcing is 3.5 W for an albedo change of 1%, which corresponds grossly to about 1 K change). If now, feedback included, the CO2 drive of 3.2 W (doubling) gives rise to a global temperature increase of 6 K (fear monger's preference), then so would then a 1% change in albedo, no ? A 1% change in albedo would then give rise to a 6K change in global temperature, wouldn't it ?


Proofs in Mathematics are very different from ones in any applied science. Different theories of gravitation, and different ways to unify it with other forces is under constant and prolific investigation. But if you drop a carton of eggs, it will fall to the ground.


The scientific method is the same everywhere. There are 2 kinds of proofs: by direct deduction from known facts, using strictly logical reasoning, and falsification of alternatives (reductio ad absurdum). Truth is not easier to establish when proof is more difficult to obtain. This is why one should remain modest with one's conclusions, and remain critical of one's theories. This is the cornerstone of scientific inquiry, it is what Feynman pointed out, and it is what I find lacking too much in the whole attitude towards AGW. Which is a pity, because it is an interesting scientific adventure and a challenging problem.

Again, all my attacks may make you think that I'm an AGW denier. I'm not - as should be clear. I'm just trying to find out how certain it has been established and up to now, I'm disappointed: my extremely elementary remarks should have been dealt with clearly because it should have been the first inquiries the AGW people should have done for themselves, if they had a truely scientific agenda. I suspect a big difference between the actual certainty and the displayed certainty. And that worries me.

[LURCH]

Just checking in with the OP;
There has been much controversy concerning Global Warming: sun spot activity, only heat radiation at 15 microns being trapped by CO2, vast amounts of greenhouse gases going intot he atmosphere from exploding volcanos and the general cyclical nature of climate change have attempted to explain the insignificance on human interaction on the environment as having a significant effect on GM.

I came across documentary which made reference to how 'Chaos Theory' explained the significant effect of human interaction on climate change. Can someone give some elaboration on this?

McHeathen (if you're still reading this), do you feel that this question has been answered?

[vanesch]

Just checking in with the OP;


McHeathen (if you're still reading this), do you feel that this question has been answered?

It may sound as if the OP's question hasn't been addressed and that we (I being part of that) are guilty of leading this thread off-topic. But in fact, that's not true. By questioning the standard AGW theory's basic hypothesis, namely, the principal drive behind climate change is human-produced CO2 (mainly fossil-fuel burning), and by looking at what the AGW proponents can (or cannot) give us as an answer, this opens (or closes) the case for climate being driven by a more complex dynamics (which might, or might not, have a chaotic behavior).

Indeed, if there is a clearly established causal and deterministic link between human-pumped CO2 and global warming, then the case for chaos is small. We have a simple, almost linear, cause-effect relationship: the more we pump CO2, the more it will warm. Period. That doesn't mean that there cannot be small oscillations and corrections and vibrations, driven by a simple, or a complex and even chaotic system, but the overall dynamics is relatively simple.
If, on the other hand, the case for this simple human-pumped CO2 --> delta-T is less secure than some AGW proponents would like to present it, then this allows us to look more into the detailled mechanics of the entire dynamics of global temperature and climate. We could then find *another* simple relationship, or we could find a more complex dynamics, in which human-induced CO2 might, or might not, play an important (but more complex) role. This dynamics might, or might not, display elements of chaotic behavior.

[vanesch]

Well, I've pointed you to a few papers that estimate this very parameter.


I re-read chapter 9, I admit I didn't bother looking up the papers. What's done in chapter 9 to estimate the climate sensitivity of human-caused greenhouse gasses ? Different models with free parameters are taken, and using, I suppose, Maximum Likelihood estimators, or even better, Bayesian estimators with a priori probabilities for the parameters, fitted to data that the models were supposed to predict as a function of input functions, probability densities were estimated for the model parameters in the sense, I suppose of the maximum likelihood method.

That's exactly what I said. You *assume* a certain behavior, and then you fit this to the data. For sure it is a good way of tuning your model to the data. However, one has to be extremely careful with this technique: it doesn't prove at all the physical hypotheses that are part of the model. Especially, this technique doesn't separate correlations from causal relationships.

Of course, in as much as this technique, when applied to a variety of data and a variety of settings (ocean temperatures, paleoclimate, recent climate, special events such as volcanic eruptions, etc...) all come up with a similar and narrow parameter probability distribution (say, with an error of 5% or so), and in as much that using the parameter estimations on one kind of data predict correctly the behavior of another set of data, one can start gaining confidence in at least the predictive value of the model - at least within the range of data for which it has been tested, and hence in its conceptual principles (in the theory that was behind the model).

It gives confidence, true. It is certainly suggestive. But there are dissonances. For instance, and the funny thing is that I didn't pick that out (honestly) because it is dissonant, but because it comes very close to the thought experiment I proposed earlier (with the albedo), a genuine test of sensitivity to radiative forcing is given by totally different events which introduce such a forcing, like volcanic eruptions. And there, we find "In contrast, an analysis by Douglass and Knox (2005) based on a box model suggests a very low climate sensitivity (under 1 degree) ..."
Of course, there has been an anti-publication to this, that suggests that this method underestimates sensitivity. Very well possible.

Nevertheless, I'm left with my original feeling. This is parameter fitting of models to data. That doesn't prove beyond reasonable doubt that the hypotheses of the models are correct, that the models don't miss anything or that the causal relationships in the models are correct. It could be. Or it could be that they contain enough flexibility to fit the data. That they contain enough liberty and nevertheless are constrained enough to distill correct correlations between input and output as in the data. BTW, that's exactly what you do with neural network models (which are not based upon any causal relationship or any physical property). Neural networks contain enough liberty to fit a rather large dynamical space, and "educating them" (fitting their parameters to time series) often distills a more or less correct input-output relationship, at least within the domain of the training set. But nobody considers the fitted parameters as representing anything physical.
Now, of course if the model is physics-inspired, and if all relevant relationships are implemented, then these fitted parameters DO have a physical meaning.

That's however not a *proof* of the correctness of the assumptions that lie at the basis of the model. It is a sensible thing to do. It's maybe the only sensible thing one can do. But my former professor of theoretical mechanics once told us: give me any 12-parameter model, and I'll fit an elephant. Add a 13th parameter, no matter which one, and I'll let his trump swing.

EDIT: to add to this: what is annoying in this way of doing things - although I can understand that one can't do anything else yet - is that the climate sensitivity is set as a free parameter, and is not calculated ab initio, by using all the physics we know. If it were calculated ab initio, had a fixed value, and it turned out that the data could be explained with this value, then this would have been a stronger case. But now that it is a free parameter, and hence can be "misused" by the model to try to accomodate for *other* effects which have not been implemented, it is harder to accept the value of this fit as both a proof of the causality on which the model is based, AND of the value of this parameter.

A simplistic example might illustrate this. Suppose that I have input data X, and output data Y. Now, suppose that in reality, there's a relationship between X and Y which goes as, say, Y = a X^2 + b X. But suppose now that we THINK that the relationship is Y = c X and that we ignore the a X^2 component (we didn't think of it, say). Now suppose that there is a physical reason, a causal relationship that has a meaning, and that is responsible for the b X term. If we are going to fit the real datacouples to this model, we will of course find a value of c. If the range of X is small enough, c will be close to (a X_av + b), and the performance of our model will not be too bad. We think it is an estimate of b. We will think that we have not only established the "law" Y = c X, but we think that we have also identified the value of whatever was this causal relationship. In other words, we think we've estimated a physical constant. We can apply, IMO, very similar comments to what is actually done in chapter 9, and we will find similar "confirmations". But we have it all backward, and although our model will do good work in the small range of X (around X_av) where it has been "trained", for, say, a doubling of X, it will be totally off. Our estimation of the "physical effect" given by b is also totally off.

This is of course a simplistic case, but it illustrates the kind of problem I see with the approach presented there when it is used to prove a causal relationship.

[Andre]

Talking about models and limitations

http://www.sciencedaily.com/releases/2007/12/071211101623.htm

A new study comparing the composite output of 22 leading global climate models with actual climate data finds that the models do an unsatisfactory job of mimicking climate change in key portions of the atmosphere...cont.

[vanesch]

Just for fun - I don't think it is really accurate. I used MODTRAN (using the web interface http://geosci.uchicago.edu/~archer/cgimodels/radiation.html ) to mimick the case of Mars. This was just a very quick thing, but if you put every greenhouse gas to 0 (including water vapor) and you put a ground offset of -60 degrees then you find (using tropical atmosphere - that's meaningless of course here) 173.14 W/m2. Now, if you add 7000 ppm (7 mbar) of CO2, then this falls to 163.7 W/m2, and you need to increase the ground temperature with 4.5K to compensate: at -55.5 you find again 173.3 W/m2.

Now, this is of course wrong for different reasons: first of all, the line widths will be different due to different Doppler broadening, and second, there's no oxygen and nitrogen. Also the assumptions of "tropical atmosphere" are wrong of course. But it gives a rough idea, and that rough idea is correct.

I had read somewhere that the greenhouse effect on Mars is around 6K (but with a large margin of error, something like 2 - 10 K), so that seems to be compatible with the purely optical effect given by modtran.

EDIT: ah, here it was: http://www.ess.uci.edu/~yu/class/ess200a/lecture.2.global.energy_cycle.pdf

EDIT 2: another fun experiment is the following. Take the current tropical atmosphere. We find, at 300 K an outgoing radiant flux of 287 W/m2. Next, put all greenhouse gasses to 0. For 300 K we now find an outward radiant flux of 398 W/m2. If you now decrease the temperature by 25 K, you find an outward flux again of 288 W/m2. So the purely optical effect, as calculated by MODTRAN, can explain a greenhouse effect of 25 K. That's pretty good, because the real greenhouse effect is 33 K. We only need "feedback amplification" of 33%, not the 200% to 800% as given by climate sensitivity.
I know, I know, this is waaaay too simple. I know. It is no proof that amplification factors cannot be stronger. But it indicates why one needs solid proof of it.

[Bored Wombat]

That's pretty good, because the real greenhouse effect is 33 K. We only need "feedback amplification" of 33%, not the 200% to 800% as given by climate sensitivity.

Water vapour is the lion's share of your 200% to 800% feedback, which is already included in MODTRAN.

[vanesch]

Water vapour is the lion's share of your 200% to 800% feedback, which is already included in MODTRAN.

You seem to forget that modtran gives only about 0.8 K for the radiative forcing of a doubling of CO2 then. Maybe you meant that the main greenhouse effect comes from water vapor. I agree with that. I wasn't implying that.

The 200% to 800% amplification is the parameter-fitted 1.5 to 6 K climate sensitivity versus the modtran-given 0.8K increase. What I meant was that modtran doesn't do so badly, for Mars, as well as for the earth. Of course I know this is too simplistic: modtran is simply calculating the optical effect in a 1-dim atmosphere in which the only transport mechanism is radiation and for which certain equilibrium conditions are taken. But given that it is ab initio (that means, it is all known physics, there are no "free fitting parameters"), and given the good performance (right ballpark for earth greenhouse effect and for Mars greenhouse effect), anything that claims to *seriously* deviate from it needs substantial proof. And fitting a free-parameter model is less physical to me than having ab initio physics-based calculations, which, given the simplicity of the setup, give remarkably accurate results.

[vanesch]

Water vapour is the lion's share of your 200% to 800% feedback, which is already included in MODTRAN.

Mmm, maybe I misunderstood you. Maybe you are implying that the modest amount of CO2 is the reason why there is a certain amount of water vapor in the atmosphere. If we would remove all CO2, then all or a large fraction of the water vapor would also disappear (for an amplification factor close to 8). Well, the simple case is implemented in MODTRAN where relative humidity is used instead of constant water vapor.
For our tropical atmosphere, we go from 280 ppm and 289.2 W/m2 to 560 ppm and 286 W/m2 at 300 K (that's our famous 3.2 W/m2 forcing for a CO2 doubling), and we now have to increase the surface temperature not by 0.8K but by 1.5K (because heating up gives more water vapor in the atmosphere and hence more greenhouse effect).

So we get about a 87% extra feedback this way, true. That's not the 800%. It comes close to the 200%, if this relative humidity doesn't do anything else. But increasing the absolute water vapor pressure increases things like convection (it is the working principle of a cooling tower!). So it is not even said that this feedback is really there.

So using this feature, we get a cllimate sensitivity of not 0.8K but of 1.5K. And that's the highest modtran can do.

[Andre]

Mmm, maybe I misunderstood you. Maybe you are implying that the modest amount of CO2 is the reason why there is a certain amount of water vapor in the atmosphere. If we would remove all CO2, then all or a large fraction of the water vapor would also disappear (for an amplification factor close to 8). Well, the simple case is implemented in MODTRAN where relative humidity is used instead of constant water vapor.
For our tropical atmosphere, we go from 280 ppm and 289.2 W/m2 to 560 ppm and 286 W/m2 at 300 K (that's our famous 3.2 W/m2 forcing for a CO2 doubling), and we now have to increase the surface temperature not by 0.8K but by 1.5K (because heating up gives more water vapor in the atmosphere and hence more greenhouse effect).

So we get about a 87% extra feedback this way, true. That's not the 800%. It comes close to the 200%, if this relative humidity doesn't do anything else. But increasing the absolute water vapor pressure increases things like convection (it is the working principle of a cooling tower!). So it is not even said that this feedback is really there.

So using this feature, we get a cllimate sensitivity of not 0.8K but of 1.5K. And that's the highest modtran can do.

Would you please substract the energy, required for the enhanced evaporation rate to maintain the higher humidity, from the energy available to heat the surface?

[vanesch]

Would you please substract the energy, required for the enhanced evaporation rate to maintain the higher humidity, from the energy available to heat the surface?

Why would I ? Once the quantity of water is in the atmosphere, the latent heat of evaporation will equal the latent heat gained back during precipitation, no ? If a closed bottle containing water and air is brought to a higher temperature, then of course during the initial heating, you have to take into account the heat capacity and the latent heat of evaporation, but once equilibrium is reached, there's no need anymore for a power influx to maintain a higher partial pressure of water vapor.

[Andre]

Why would I ? Once the quantity of water is in the atmosphere, the latent heat of evaporation will equal the latent heat gained back during precipitation, no ?

No, you basically accellerate the water cycle. Precipitation is colder than the ambient temperature during falling into lower warmer levels (lapse rate). So it doesn't bring energy back to the surface. The increased latent heat released at altitude is emitted and partially escapes into space, not helping the required higher evaporation rate to sustain the quicker water cycle.

Also think in daily cycles. In many parts of the world, there is cumulus type clouds at daytime and no clouds at night time, During the day the decreasing albedo is restricting the temperature rise at the Earth surface. If the water cycle is acceralerated, the increase in cloudiness will limit the temperature rise even more as a substantial negative feedback, while at night time out radiation is changed only very little(assuming a small decrease in optical depth for IR radiation) It's just as if you turn the air conditioner to more cooling.

[vanesch]

No, you basically accellerate the water cycle. Precipitation is colder than the ambient temperature during falling into lower warmer levels (lapse rate). So it doesn't bring energy back to the surface. The increased latent heat released at altitude is emitted and partially escapes into space, not helping the required higher evaporation rate to sustain the quicker water cycle.

Also think in daily cycles. In many parts of the world, there is cumulus type clouds at daytime and no clouds at night time, During the day the decreasing albedo is restricting the temperature rise at the Earth surface. If the water cycle is acceralerated, the increase in cloudiness will limit the temperature rise even more as a substantial negative feedback, while at night time out radiation is changed only very little(assuming a small decrease in optical depth for IR radiation) It's just as if you turn the air conditioner to more cooling.

Yes, but these are more complicated mechanisms, which are part of more involved models taking into account cloud formation, convection, albedo changes etc...

I was talking about the simple model of a static (no air movement, no convection) monophase (no clouds) optical model as done in modtran. In such a model, one doesn't need to subtract the evaporation latent heat once equilibrium with the new radiative forcing is established.

[Robert Elliso]

‘The climate system is particularly challenging since it is known that components in the system are inherently chaotic; there are feedbacks that could potentially switch sign, and there are central processes that affect the system in a complicated, non-linear manner. These complex, chaotic, non-linear dynamics are an inherent aspect of the climate system.’ (IPCC TAR s14.2.2.1 - http://www.ipcc.ch/ipccreports/tar/wg1/504.htm)

‘Modern climate records include abrupt changes that are smaller and briefer than in paleoclimate records but show that abrupt climate change is not restricted to the distant past.’ (Abrupt Climate Change: Inevitable Surprises, 2002, NAP, p19 - http://books.nap.edu/openbook.php?record_id=10136&page=19).

A dynamic theory of ocean/climate states (http://www.nosams.whoi.edu/PDFs/papers/tsonis-grl_newtheoryforclimateshifts.pdf) confirms that climate on decadal timescales is an emergent property of complex and dynamic Earth systems. "You go from a cooling regime to a warming regime or a warming regime to a cooling regime. This way we were able to explain all the fluctuations in the global temperature trend in the past century," Anastasios Tsonis said.