Playing Devil's advocate on climate [Archive]

Andre

Sep19-09, 05:16 AM

Isn't that the 'holy' duty of science, to play devils advocate? Either strenghten the human corporate knowledge, if there are no flaws to find; or stop going into the wrong direction if the ideas turn out to be flawed.

That has everything to do with falsifiability and reproduceability and it never stops. You can't prove a theory to be right but you can falsify it according to Popper (http://www.experiment-resources.com/falsifiability.html).

While falsifiabiltiy is rather rigid and can be disputed on statements that are too black and white, it doesn't warrant that theories should be shielded against attempts to falsify it. But much more significant, if that happens, what does that say about the trustworthiness of said theory amongst their adherents? Anybody noticed how many folk devils (http://www.arts.auckland.ac.nz/online/sociol318/week4.html) we have nowadays, known as deniers? Could that be the result of many ad hominem attacks against people who are merely doing their job?

There is yet another way to shield global warming effectively against falsification, that's simply by declaring what ever happens, cooling or warming, to be global warming anyway, always (http://www.aber.ac.uk/media/Students/hrb9701.html):

Professor Mojib Latif, from the Leibniz Institute of Marine Sciences at Kiel University in Germany, has been looking at the influence of cyclical changes to ocean currents and temperatures in the Atlantic, a feature known as the North Atlantic Oscillation. When he factored these natural fluctuations into his global climate model, professor Latif found the results would bring the remorseless rise in average global temperatures to an abrupt halt.

"The strong warming effect that we experienced during the last decades will be interrupted. Temperatures will be more or less steady for some years, and thereafter will pickup again and continue to warm".

However, if something is not falsifiable anymore, is it still science?

Also, what strong warming anyway?

http://www.ssmi.com/data/msu/graphics/plots/sc_Rss_compare_TS_channel_tlt_v03_2.png

Source: http://www.ssmi.com/msu/msu_data_description.html#figures

vanesch

Sep19-09, 06:48 AM

Andre

Sep19-09, 07:18 AM

The problem is, Andre, that the "deniers" have also a theory to defend, namely that extra consumption of fossil fuels and the exhausted CO2 in the atmosphere has NO possibility to give rise to any observable warming over several hundreds of years. That's also a pretty strong statement that should be defended.

Not so sure about that, Patrick. "The Deniers" (http://www.amazon.com/Deniers-Renowned-Scientists-Political-Persecution/dp/0980076315) whom I know, do not attempt to deny basic statistical physical principles. It would be rather foolish to ignore physical processes either way. Or could it be that repeated strawman arguments from the remorseless propaganda have rooted deeply to give that impression?

As to the second theory, the difficulty is now to establish HOW MUCH warming it could cause.
Is it going to be 0.1 degree, or 1 degree, or 2 degrees, or 5 degrees, or 10 degrees, or 15 degrees or ... ? That's a matter of numerical accuracy of the theoretical models.

There are basically three things that need to be separated,

First of all the political fallacatic implication that any position on climate should translate to a position on energy issues. It's not. I bought the world recordholder gas mileage car for that reason. But if you make that implication, it also means that, if 'global warming' is falsified that it would also give the impression that energy considerations are also falsified. Try to stop that, for one, if a new little ice age would start.

Second, if global warming was to be true, why do we think that it would lead to catastrophies? There are several indications that nature and mankind benefitted significantly from mild climate conditions, to begin with the PETM (Paleocene Eocene Thermal Maximum), 55.3 million years ago, giving an explosion of new species, conquering the world, and more recently the Holocene Thermal Maximum, ca 9000-5000 years ago. This can be attributed to Earth insolation cycles, but it's also when the early civilisations started to prosper and devellop. Also the Medieval warm period around 800-1000AD marked the end of the dark ages in which west Europe civilisation had a huge downfall.

Third, the physics itself. I don't think that there are many arguments against a basic climate sensitivity of about one degree celsius per doubling CO2. The main dispute is about the accumulations of all feedbacks to be positive or negative. It's a bit hard to model all that and 'retrodict' the assumed the climate cycles of the recent geologic past with that, either with positive or negative feedback. That's what the discussion should be about.

sylas

Sep19-09, 07:24 AM

I don't think that there are many arguments against a basic climate sensitivity of about one degree celsius per doubling CO2.

With a tiny handful of exceptions, almost everything ever published that has given constraints on sensitivity has been in the range of about 1.5 to 4.5 degrees celcius per doubling.

The point of being able to argue another side is I presume to show that you are at least aware of the other side!

A good overview of the state of play with respect to sensitivity is available in thread A low likelihood for high climate sensitivity. The papers discussed in that thread -- Annan and Hargreaves (2006, and 2009) and Roe and Baker (2007) -- are particularly useful because they pull together conclusions based on many independent published estimates. (And just to be clear; the usual meaning of "high sensitivity", and the meaning used in all the various papers used in that thread, is sensitivity above 4.5 or so. Roe and Baker argue that it is hard to rule out such high values. Annan and Hargreaves argue that you can rule out such high values, with strong confidence.)

If people are interested in what scientific debate looks like, there's a very relevant example in msg #47 of thread "Estimating the impact of CO2 on global mean temperature". This deals with a very low sensitivity estimate made by Schwartz in 2007, giving the likely range of possible values as 0.6 to 1.6. There were a number of responses published in the same journal, and then Schwartz acknowledged the corrections, and revised his estimate to the range 0.9 to 2.9, which is still low, but a bit more reasonable.

That's what a real scientific debate looks like. People don't just argue for something they don't agree with! Rather they look into counter arguments and try to understand them. Frequently this involves being able to show where the argument is actually incorrect, on its own merits. THAT'S the real sign of science at work. It's not about seeing the other side in the sense of recognizing it and making it part of your own position, but about being able to look at the other side directly on its merits.

The "trench warfare" distinction is not so much about holding to a particular view. Scientists do that with vengeance! It's about engaging directly with criticism. Where debate ceases to be scientific is where one side or the other simply repeats the same talking points endlessly without dealing with direct refutations. If you CAN deal with refutations, then there's nothing unscientific about continuing to hold a firm line.

Cheers -- sylas

vanesch

Sep19-09, 07:53 AM

There are basically three things that need to be separated,

Ok, let's go.

First of all the political fallacatic implication that any position on climate should translate to a position on energy issues. It's not. I bought the world recordholder gas mileage car for that reason.

Partly true, but actually, it doesn't matter in the scientific debate. The *societal consequences* of one or other outcome of the global warming debate have, in them selves, not the slightest impact on the scientific debate itself. Actually, I'm not even much interested in it (I only take on the stance there when I discuss with the Green Brigade, because it's an argument they cannot counter). However, if severe global warming turns out to be not totally improbable, one has to take into account its risk. If the (bayesian) probability of severe global warming is, say, 3%, that means that one still has a risk of 0.03 times the consequence of this global warming, so this might still inspire to get away from fossil fuels earlier than on a purely economic motivation. But all of this is NOT part of the scientific debate over global warming.

In other words, the discussion about whether there is global warming or not has nothing to do with its eventual consequences. I think that's the first thing to agree upon. It is not because an illness is severe or not, that this changes the diagnosis.

Second, if global warming was to be true, why do we think that it would lead to catastrophies? There are several indications that nature and mankind benefitted significantly from mild climate conditions, to begin with the PETM (Paleocene Eocene Thermal Maximum), 55.3 million years ago, giving an explosion of new species, conquering the world, and more recently the Holocene Thermal Maximum, ca 9000-5000 years ago.

Again, that doesn't really matter in the discussion. It's part of the earlier stance. Whatever the consequences, they don't influence the inquiry. But there's no waterproof guarantee that warming will necessarily be positive *everywhere*. Those in power (we), might be on the negative receiving end, and we wouldn't like that. That wouldn't compensate by others having better living conditions if ours get worse. It is in general, why we don't like unplanned change.

Third, the physics itself. I don't think that there are many arguments against a basic climate sensitivity of about one degree celsius per doubling CO2. The main dispute is about the accumulations of all feedbacks to be positive or negative.

Indeed. But that's a matter of quantitative inquiry, because we balance a lot of things, some badly understood. It is a matter of sufficient accuracy. But even 1 degree is, in my book, "climate change". Even 0.5 degree. All the rest is a matter of quantitative accuracy, but not of principle.

Even someone accepting the possibility of 0.5 degree of systematic warming is, in my book, someone who accepts "climate change". To me, a "denier" is someone who thinks that it is utmost impossible that human CO2 exhaust can have *any noticeable influence whatever* on the climate system - meaning it should be below the level of measurement accuracy (which I take, arbitrarily, to be of the order of 0.1 degree).

It's a bit hard to model all that and 'retrodict' the assumed the climate cycles of the recent geologic past with that, either with positive or negative feedback. That's what the discussion should be about.

Indeed. But it is a matter of quantitative modeling now. We're outside of the "deniers-heaters" debate. We're accepting that climate change is there, and we're trying to calculate how much.

However, the paleoclimate is just a testcase, and I don't know how much it is pertinent. What should eventually be done, is predictions "from first principles" alone, with sufficient accuracy and confidence, that it includes all of the relevant dynamics. The observations are then just secundary, as an eventual test case.

Andre

Sep19-09, 08:37 AM

Well it all boils down to how the perception of the public is shaped:

For instance:
http://www.ucsusa.org/global_warming/

Global warming is one of the most serious challenges facing us today. To protect the health and economic well-being of current and future generations, we must reduce our emissions of heat-trapping gases by using the technology, know-how, and practical solutions already at our disposal.

or 'translated' to the perception:

1: We are causing global warming.

Probably, but so are a number of other factors, the weight of which we only begin to perceive, if at all. So is whatever we do, comparable to the weight of other factors?

2: if we don't do anything, then it could lead to catastrophes

and that does make reference to paleoclimate significant. There is no evidence whatsoever from the paleo records for catastrophes associated with warming for whatever reasons or would we know if the negative elements (more ocean) outweights the advantages (more biomass, milder climates in large parts of the world (like Siberia perhaps)

3: If we stop emitting, we can deal with the problem

Can we? Is it a problem? We have not determined how much antropogene activities contribute, so how can we conclude that stopping emission would "save the climate" (http://www.google.nl/search?source=ig&hl=nl&rlz=&q=save+the+climate&btnG=Google+zoeken&meta=lr%3D&aq=f&oq=).

Just for counter indication: suppose that we are heading for a new (little) Ice Age, would extra emission prevent catastrophic global cooling?

If we need to stop emitting CO2, then why not for the sake of fully legimate reasons, like economical necessity, energy surety and security, etc.

Andre

Sep19-09, 09:05 AM

With a tiny handful of exceptions, almost everything ever published that has given constraints on sensitivity has been in the range of about 1.5 to 4.5 degrees celcius per doubling.
.......

I was arguing about a basic sensitivity for doubling, not for the assumptions for a final sensitivity including feedbacks.

Let's grab that envelope again and do some very basic calculations.

If the average global temperature is 15C or 288K then according to Stefan Bolzmann (http://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law) for a 'black body' this translates to an equivalent black body irridiance ~389.9 w/m2.

Now if we would double CO2 we assume an increase of the irridiance with what? 3.7 w/m2? or 5 w/m2 or 10 w/m2 (http://www.google.nl/search?source=ig&hl=nl&rlz=&q=sensitivity+CO2+doubling+w%2Fm2&meta=lr%3D&aq=f&oq=) to resp ~393.6 or ~394,.9 or 399.9 w/m^2. This would correspond to temperature rises of 0.7K or 0.9K or 1.8K respectively (assuming 100% absorption). I hear 3.7 w/m2 a lot, so 1.0K does not seem too odd as simple basic value. The question remains if there is enough positive feedback to boost radiation to double orders of magnitude.

sylas

Sep19-09, 09:45 AM

I was arguing about a basic sensitivity for doubling, not for the assumptions for a final sensitivity including feedbacks.

OK, I understand you now. I think this is more usually called "Planck response", or "base response". Since this is what you are speaking of, I concur.

The Planck response, or base response is roughly 1 -- or if we are more precise it is around 1.12 to 1.16. The simple blackbody estimate will get into the ballpark okay; a more careful account is given with references in the latter part of msg #171 of thread "Need Help: Can You Model CO2 as a Greenhouse Gas (Or is This Just Wishful Thinking?)".

It turns out that you can get into the ball park more closely using 4Q/T where Q is the emission from Earth (about 240 W/m2) and T is the mean surface temperature (about 288K). (The Planck response of a simple blackbody with the same emission to space as the Earth would use T as 255K, being the mean emission temperature.) This gives 0.3 K/(Wm-2). Converting units this is 1.11 K/2xCO2, with 2xCO2 being 3.71 Wm-2, as you also note.

Cheers -- sylas

vanesch

Sep19-09, 10:13 AM

1: We are causing global warming.

If you translate this into: our actions give/will give rise to a measurable higher temperature than it would be without them, I think that is the essence of the discussion. Whether this is the MAIN cause of change is another issue: for sure a gigantic volcano eruption, or the impact of a meteorite, or other things of the kind, are always possible.

What the discussion is about is whether the change is noticeable. Whether it will be warmer with than without.

2: if we don't do anything, then it could lead to catastrophes

Again, that's not part of any scientific debate by itself.

There is no evidence whatsoever from the paleo records for catastrophes associated with warming for whatever reasons or would we know if the negative elements (more ocean) outweights the advantages (more biomass, milder climates in large parts of the world (like Siberia perhaps)

Ok, but there hasn't been a technological and economical society like there is one today either. So the impact on global economy is not to be read from these paleo observations.
The question is whether it will have a negative economic impact on the economic powers that be. Will global warming have a positive or negative impact on the tourism in the south of Spain, for instance ? You can't find anything out like that using paleo data. Will potential climate change be beneficial for the Bourgogne winegards ? It will probably be negative, because in order to continue to make the wine they make now, they need as small a change in parameters as possible.

But again, that's not part of the scientific discussion, at all.

3: If we stop emitting, we can deal with the problem

You shouldn't think - in the scientific debate - about climate change as a "problem", but just as an "outcome". So the answer here is: if we stop emitting now, will this significantly alter the effect as compared to if we don't stop emitting, or even emit more ?

Again, this is a matter of quantitative accuracy, but I would think that the answer if fairly obvious, no ? It will make a numerically significant difference. You will be able, instrumentally, to distinguish between both.

Just for counter indication: suppose that we are heading for a new (little) Ice Age, would extra emission prevent catastrophic global cooling?

If we need to stop emitting CO2, then why not for the sake of fully legimate reasons, like economical necessity, energy surety and security, etc.

But, in the scientific debate about climate change, there's nothing we should or shouldn't do. There's just the question of how much, in what circumstances. Whether this is "good" or "bad" and whether we should encourage it or avoid it, is not a scientific debate. It should be totally separated from it.

What's "good" and what's "bad" depends on one's PoV and hence is not scientifically debatable.

For fun: http://en.cop15.dk/news/view+news?newsid=2099

Greenland wants to emit more CO2. One can understand them :smile:
(ok, they don't openly say they want the world to heat, but I'm sure they don't lie awake from it...)

So again, the *effect* of fossil fuels and other human-made greenhouse gasses on the climate is a scientific matter, which stands in no relation to how one should react to it. The effect is independent of whether it is desirable or undesirable. And that's where the discussion is about.

Saul

Sep19-09, 11:26 AM

Ok, let's go.

Partly true, but actually, it doesn't matter in the scientific debate. The *societal consequences* of one or other outcome of the global warming debate have, in them selves, not the slightest impact on the scientific debate itself. Actually, I'm not even much interested in it (I only take on the stance there when I discuss with the Green Brigade, because it's an argument they cannot counter). However, if severe global warming turns out to be not totally improbable, one has to take into account its risk. If the (bayesian) probability of severe global warming is, say, 3%, that means that one still has a risk of 0.03 times the consequence of this global warming, so this might still inspire to get away from fossil fuels earlier than on a purely economic motivation. But all of this is NOT part of the scientific debate over global warming.

In other words, the discussion about whether there is global warming or not has nothing to do with its eventual consequences. I think that's the first thing to agree upon. It is not because an illness is severe or not, that this changes the diagnosis.

Again, that doesn't really matter in the discussion. It's part of the earlier stance. Whatever the consequences, they don't influence the inquiry. But there's no waterproof guarantee that warming will necessarily be positive *everywhere*. Those in power (we), might be on the negative receiving end, and we wouldn't like that. That wouldn't compensate by others having better living conditions if ours get worse. It is in general, why we don't like unplanned change.

vanesch,

In the past civilization flourished during the warm periods. There was starvation during the cold periods. Air holds roughly 6% more water for each 1C it is warmer. 70% of the planet is covered with water. When the planet is warm there is ample rain, the biosphere expands. When the planet is cold, it is windy and dry, the biosphere contracts. At 200 ppm C3 plants stop growing. As CO2 increases C3 and C4 plants require less water and make more effective use of sunlight. CO2 is added (2000 to 3000 ppm) to greenhouses to increase yield and reduce time to yield.

It appears based on the science (measurement of upper atmosphere temperatures shows the current planetary warming was not caused by GWG.) that the atmosphere saturates with respect to additional CO2. There have been periods of planetary glaciation when CO2 levels were as high as 2000 ppm. CO2 does not correlate with planetary temperature in the geological past.

It appears the planet is about to abruptly cool not warm. There is are hundreds cycles of long term abrupt planetary cooling events that correlate with cosmogenic isotope changes (Traced out until 1 million years ago which is the limit of the paleo record). The cosmogenic isotope changes occur due to solar magnetic cycle changes which increases the amount of galactic cosmic rays (GCR, mostly high speed protons) that strike the earth's atmosphere.

The GCR create muons which in turn create ions in the atmosphere. More ions more planetary cloud cover. Particularly over the ocean which is ion poor. Rain removes ions so unless the ions are replenished cloud formation is abated.

http://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Carbon14_with_activity_labels.svg/800px-Carbon14_with_activity_labels.svg.png

http://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Carbon14_with_activity_labels.svg/800px-Carbon14_with_activity_labels.svg.png

GCR levels have increased 18%, however cloud cover has not as yet increased.

There is a second mechanism by which the sun modulates planetary cloud cover, electroscavenging. Solar wind bursts create a space charge in the ionosphere which removes ions by a process called electroscavenging.

The 20th century warming was caused by electroscavenging. The solar wind bursts in addition to removing ions from the atmosphere disturb the geomagnetic field. Ak is a measurement of the amount of disturbance of the geomagnetic field and the time delay of the effects of the solar wind bursts.

There is direct correlation of the complete 20th century warming with Ak.

http://cosmicrays.oulu.fi/webform/query.cgi?startdate=2004/07/29&starttime=00:00&enddate=2009/08/29&endtime=02:44&resolution=1440&picture=on

http://www.agu.org/pubs/crossref/2009/2009JA014342.shtml

If the Sun is so quiet, why is the Earth ringing? A comparison of two solar minimum intervals.
The present solar minimum is exceptionally quiet, with sunspot numbers at their lowest in 75 years and solar wind magnetic field strength lower than ever observed.

Despite, or perhaps because of, a global weakness in the heliospheric magnetic field, large near-equatorial coronal holes lingered even as the sunspots disappeared. Consequently, for the months surrounding the WHI campaign, strong, long, and recurring high-speed streams in the solar wind intercepted the Earth in contrast to the weaker and more sporadic streams that occurred around the time of last cycle's WSM campaign.

In response, geospace and upper atmospheric parameters continued to ring with the periodicities of the solar wind in a manner that was absent last cycle minimum, and the flux of relativistic electrons in the Earth's outer radiation belt was elevated to levels more than three times higher in WHI than in WSM. Such behavior could not have been predicted using sunspot numbers alone, indicating the importance of considering variation within and between solar minima in analyzing and predicting space weather responses at the Earth during solar quiet intervals, as well as in interpreting the Sun's past behavior as preserved in geological and historical records.

Saul

Sep19-09, 11:32 AM

http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..969G.pdf

Once again about global warming and solar activity K. Georgieva, C. Bianchi, and B. Kirov

We show that the index commonly used for quantifying long-term changes in solar activity, the sunspot number, accounts for only one part of solar activity and using this index leads to the underestimation of the role of solar activity in the global warming in the recent decades. A more suitable index is the geomagnetic activity which reflects all solar activity, and it is highly correlated to global temperature variations in the whole period for which we have data.

In Figure 6 the long-term variations in global temperature are compared to the long-term variations in geomagnetic activity as expressed by the ak-index (Nevanlinna and Kataja 2003). The correlation between the two quantities is 0.85 with p<0.01 for the whole period studied.It could therefore be concluded that both the decreasing correlation between sunspot number and geomagnetic activity, and the deviation of the global temperature long-term trend from solar activity as expressed by sunspot index are due to the increased number of high-speed streams of solar wind on the declining phase and in the minimum of sunspot cycle in the last decades.

See section 5a) Modulation of the global circuit in this review paper, by solar wind burst and the process electroscavenging where by increases in the global electric circuit remove cloud forming ions.

The same review paper summarizes the data that does show correlation between low level clouds and GCR.

http://www.utdallas.edu/physics/pdf/Atmos_060302.pdf

sylas

Sep19-09, 11:58 AM

Skyhunter

Sep19-09, 12:10 PM

There is no evidence whatsoever from the paleo records for catastrophes associated with warming for whatever reasons or would we know if the negative elements (more ocean) outweights the advantages (more biomass, milder climates in large parts of the world (like Siberia perhaps)

Permian Extinction (http://geology.about.com/od/extinction/a/aa_permotrias.htm)

Saul

Sep19-09, 12:37 PM

BLAM. There goes my irony meter.

Saul: the topic of this thread is NOT an invitation for you to just make all the same claims you have habitually made in the past. It is in fact precisely the reverse. It's about how capable people are of understanding the position they DON'T hold, as shown by their ability to make the arguments as they would be made by their opponents.

I'm not persuaded that this is all that useful an exercise as phrased; but I do take the point that scientific debate works by engaging substantively with counter positions from a position of understanding. Other contributors here are all taking up the matter of the nature of the scientific debate in general terms.

By just jumping in to restate your own perspective on a climate related topic, you've completely missed the whole point.

sylas,

Unfortunately the planet is about to abruptly cool. The beneficial warming is over.

This is not a surprise. Interglacial periods have all end abruptly. There is evidence in the paleoclimatic record of a cyclic massive external forcing function. There are dozens of published papers that outline specifically what that forcing function is.

This is a scientific discussion not a moral discussion. We are not going to solve the problem of abrupt planetary cooling by reducing anthropic produced CO2. Anthropic CO2 is one of the few beneficial changes humans are making to the biosphere.

Think of the irony of eminent abrupt planetary cooling, after decades of discussions about abrupt planetary warming.

This is of course why there are scientific revolutions. Have you read Thomas Kuhn's "The Structure of Scientific Revolutions". The AWG movement is an example of group think. When people have a position they continue to maintain that position even when the facts no longer support that position.

If there was not a glacial/interglacial cycle, cyclic abrupt climate change that correlates with cosmogenic isotope changes, lack of correlation of CO2 levels with planetary temperature in the geological past, a mechanism by which solar magnetic cycle changes affect planetary cloud cover and the geomagnetic field, evidence of cyclic geomagnetic field changes which also correlate with solar magnetic cycle changes, past civilization collapse during abrupt cooling events, the AWG "position" might be theoretically defensible.

http://upload.wikimedia.org/wikipedia/commons/c/c2/Vostok-ice-core-petit.png

http://en.wikipedia.org/wiki/File:Vostok-ice-core-petit.png

Andre

Sep19-09, 12:46 PM

Permian Extinction (http://geology.about.com/od/extinction/a/aa_permotrias.htm)

Right, it must have been pretty hot when a large part of Siberia erupted in what is known as the largest volcanic event on record, the Siberian traps. (http://www.solcomhouse.com/siberiantraps.htm)

http://www.solcomhouse.com/images/SiberiaAmphiboleFig2_550.gif

See also this (http://www.sciencemag.org/cgi/content/abstract/296/5574/1846?ck=nck) and this (http://www.springerlink.com/content/1743222152769702/)

Note that the CO2 release and warming is a proposal not supported by direct evidence. Compare this with the prospect of other very tiny mini volcanic eruptions like Yellowstone, and the projected direct causalities. The Siberian traps could just as well have released enough chemicals for direct poisening effects.

Galteeth

Sep19-09, 02:40 PM

It is interesting to me that this board seems to be dominated by those who (assuming the media and government hasn't lied to me) hold a minority position.

sylas

Sep19-09, 02:58 PM

It is interesting to me that this board seems to be dominated by those who (assuming the media and government hasn't lied to me) hold a minority position.

They're all just kidding, of course. You are seeing the consummate example of the whole principle of this thread.

Cheers -- Sylas -- who is of course secretly laughing up his sleeve and has massive investments in a proposed ski resort just out of San Diego.

Andre

Sep19-09, 03:31 PM

It is interesting to me that this board seems to be dominated by those who (assuming the media and government hasn't lied to me) hold a minority position.

So if the numbers make the difference, what, for instance, would be the score on evolution science versus creation believers? And what would that say about scientific merit?

Maybe that the first law of science is not to jump on bandwagons (http://www.fallacyfiles.org/bandwagn.html).

Anyway, this thread (http://www.physicsforums.com/showthread.php?t=256593) used to be about the real numbers. However, it seems to be modified a bit.

Skyhunter

Sep19-09, 03:46 PM

Note that the CO2 release and warming is a proposal not supported by direct evidence. Compare this with the prospect of other very tiny mini volcanic eruptions like Yellowstone, and the projected direct causalities. The Siberian traps could just as well have released enough chemicals for direct poisening effects.

Andre you ignore the evidence in your own links and make an on the fly speculation that poisonous chemicals of volcanic origins is as plausible an explanation as the ones offered by the links that you provided! If you want to propose an explanation then provide a link that supports it. Otherwise it is just being contrary for the sake of contrariness.

The second link you provided refutes your claim that there is, "no evidence whatsoever from the paleo records for catastrophes associated with warming".

The Traps were formed over 100's of thousands years by a magma plume. The SOx caused glaciations while the CO2 caused long term warming. The climate was on a seesaw.

Vulcanism was the trigger, but the hothouse climate was the primary cause of oceanic anoxia.

Human activity is altering the chemical structure of the atmosphere at a much faster rate than what occurred 250 million years ago. AGW is a radical and unprecedented experiment with the only biosphere we have. I for one am not willing to risk the planet's future and posterity on the off chance that the world's scientific community is wrong.

Galteeth

Sep19-09, 03:52 PM

So if the numbers make the difference, what, for instance, would be the score on evolution science versus creation believers? And what would that say about scientific merit?

Maybe that the first law of science is not to jump on bandwagons (http://www.fallacyfiles.org/bandwagn.html).

Anyway, this thread (http://www.physicsforums.com/showthread.php?t=256593) used to be about the real numbers. However, it seems to be modified a bit.

Wait, what? I understand your point, truth is not determined by consensus, but that example makes no sense to me. Creation "scientists" certainly do not ouitnumber evolutionists, unless you are defining anyone with christian type beliefs as a creationist, which probably isn't an accurate reflection of the number of people.

Andre

Sep19-09, 03:58 PM

Creation "scientists" certainly do not ouitnumber evolutionists.

Creation believers would probably outnumber scientists that deal with evolution directly and that's what I intended to say. I'm only trying to encourage to take a week or two and try to understand what the core matter is and what the problems are.

Andre

Sep19-09, 04:04 PM

Vulcanism was the trigger, but the hothouse climate was the primary cause of oceanic anoxia. .

That is speculation. You could just as well argue that the permanent shielding of the sun, due to the volcanic ashes, caused most live to perish. We just don't know, so everybody can project their favorite pet theories. Also because apparantly the climate principles where different then, like in the Ordovician (http://www.palaeos.com/Paleozoic/Ordovician/Ordovician.htm)

As a natural consequence, a good deal of attention has been focused on the causes of the Ordovician Ice Age. In fact, it is not easy to see how an ice age could have occurred. Atmospheric carbon dioxide levels are believed to have been 8 to 20 times their current values. This ought to have prevented anything approaching an ice age.

Skyhunter

Sep19-09, 04:30 PM

Andre,

So you don't actually read the links you post?

You make sweeping absolute statement claiming there is "absolutely no evidence", then provide a link full of the very evidence you declared does not exist!

I would posit that you are simply being contrary for the sake of contrariness.

Saul

Sep19-09, 05:03 PM

There is in paleo record abrupt cyclic cooling events that correlate with solar magnetic cycle changes. Humanity has not in recorded history experience an abrupt cooling event.

As the sun is moving rapidly to an unusual minimum it appears we will be able to observe which hypothesis is correct. Assuming the planet does as it did in the past abruptly cool, I am curious as to how long and what process the scientific change occur.

Based on the solar mechanism there should be an observable difference this winter.

To sylas or skyhunter: Is there any evidence that could disprove the AWG hypothesis?

http://www.sciencemag.org/cgi/content/abstract/292/5520/1367?ck=nck

Solar Forcing of Drought Frequency in the Maya Lowlands
David A. Hodell, Mark Brenner,1 Jason H. Curtis,1 Thomas Guilderson

We analyzed lake-sediment cores from the Yucatan Peninsula, Mexico, to reconstruct the climate history of the region over the past 2600 years. Time series analysis of sediment proxies, which are sensitive to the changing ratio of evaporation to precipitation (oxygen isotopes and gypsum precipitation), reveal a recurrent pattern of drought with a dominant periodicity of 208 years. This cycle is similar to the documented 206-year period in records of cosmogenic nuclide production (carbon-14 and beryllium-10) that is thought to reflect variations in solar activity. We conclude that a significant component of century-scale variability in Yucatan droughts is explained by solar forcing. Furthermore, some of the maxima in the 208-year drought cycle correspond with discontinuities in Maya cultural evolution, suggesting that the Maya were affected by these bicentennial oscillations in precipitation.

http://www.essc.psu.edu/essc_web/seminars/spring2006/Mar1/Bond%20et%20al%202001.pdf

Persistent Solar Influence on North Atlantic Climate During the Holocene

Gerard Bond, Bernd Kromer, Juerg Beer, Raimund Muscheler, Michael N. Evans, William Showers, Sharon Hoffmann,Rusty Lotti-Bond,1 Irka Hajdas, Georges Bonani

Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been inßuenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic 1500-year cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the
solar signals and transmitting them globally.

http://geology.geoscienceworld.org/cgi/content/abstract/30/5/455

Widespread evidence of 1500 yr climate variability in North America during the past 14 000 yr

There is debate concerning the spatial extent and magnitude of the recently identified 1500 yr climate oscillation. Existing evidence is largely restricted to the North Atlantic and adjacent landmasses. The spatial extent, magnitude, and effects of these climate variations within the terrestrial environment during the Holocene have not been established. We show that millennial-scale climate variability caused changes in vegetation communities across all of North America with a periodicity of 1650 ± 500 yr during the past 14 000 calendar years (cal yr). Times of major transitions identified in pollen records occurred at 600, 1650, 2850, 4030, 6700, 8100, 10 190, 12 900, and 13 800 cal yr B.P., consistent with ice and marine records. We suggest that North Atlantic millennial-scale climate variability is associated with rearrangements of the atmospheric circulation with far-reaching influences on the climate.

vanesch

Sep19-09, 10:48 PM

In the past civilization flourished during the warm periods. There was starvation during the cold periods. Air holds roughly 6% more water for each 1C it is warmer. 70% of the planet is covered with water. When the planet is warm there is ample rain, the biosphere expands. When the planet is cold, it is windy and dry, the biosphere contracts. At 200 ppm C3 plants stop growing. As CO2 increases C3 and C4 plants require less water and make more effective use of sunlight. CO2 is added (2000 to 3000 ppm) to greenhouses to increase yield and reduce time to yield.

Might be, but all this has nothing to do with the question of whether (and how much) the earth is going to be warmer with man-made CO2 addition rather than without.

It appears based on the science (measurement of upper atmosphere temperatures shows the current planetary warming was not caused by GWG.) that the atmosphere saturates with respect to additional CO2.

Now that's a funny statement. What could it mean ? On a radiation transport basis, it makes no sense.

There have been periods of planetary glaciation when CO2 levels were as high as 2000 ppm. CO2 does not correlate with planetary temperature in the geological past.

You mean during snowball earth events ?

It appears the planet is about to abruptly cool not warm.

Even then, would you concur that with human-added CO2 to the atmosphere, that hypothetical cooling will be less than it would be without, or not ? Because that would mean that there is (relative) AGW, no ?

vanesch

Sep19-09, 11:17 PM

To sylas or skyhunter: Is there any evidence that could disprove the AWG hypothesis?

There is a fundamental difficulty with these kinds of "historic" considerations, in that you only have one go. That's a bit like economic policy: you could ask: "is there any way to disprove that your employment policy has created jobs ?", because you don't have the "two runs" in which you can compare both: or you applied the policy, and, with everything else happening, you have a certain evolution of employment, or you don't apply the policy, and you have another evolution of employment. But you don't have both "at once" to compare them.

So the only way to truly find out, would be to have a very long term experiment, where humans put a lot of CO2 in the atmosphere, then where they cut back their emissions, then when they put again a lot of CO2 in the atmosphere etc... over times of thousands of years, and find out whether there is an observed correlation between the temperature evolutions and the emissions, when there have been a statistically significant number of cycles of emission and no emission, which, moreover must be uncorrelated with other climate events.

The other way is to have a consistent theoretical model based on first principles, where every part is well-checked, which makes accurate climate predictions given all inputs (like solar activity, volcanic activity, relevant human activity...) for hundreds of years, in which we can build confidence. This can be cut short by using paleo climate as test cases, but then we are confronted with the reliability, the accuracy and the completeness of the paleo climate proxies.

So it seems that in any case, we need the experimental record to continue for a few decades / centuries before we can say anything for sure about climate change. In the mean time, it's guessing, based upon one's faith in different theoretical constructions.

Saul

Sep20-09, 12:11 AM

There is a fundamental difficulty with these kinds of "historic" considerations, in that you only have one go. That's a bit like economic policy: you could ask: "is there any way to disprove that your employment policy has created jobs ?", because you don't have the "two runs" in which you can compare both: or you applied the policy, and, with everything else happening, you have a certain evolution of employment, or you don't apply the policy, and you have another evolution of employment. But you don't have both "at once" to compare them.

So the only way to truly find out, would be to have a very long term experiment, where humans put a lot of CO2 in the atmosphere, then where they cut back their emissions, then when they put again a lot of CO2 in the atmosphere etc... over times of thousands of years, and find out whether there is an observed correlation between the temperature evolutions and the emissions, when there have been a statistically significant number of cycles of emission and no emission, which, moreover must be uncorrelated with other climate events.

The other way is to have a consistent theoretical model based on first principles, where every part is well-checked, which makes accurate climate predictions given all inputs (like solar activity, volcanic activity, relevant human activity...) for hundreds of years, in which we can build confidence. This can be cut short by using paleo climate as test cases, but then we are confronted with the reliability, the accuracy and the completeness of the paleo climate proxies.

So it seems that in any case, we need the experimental record to continue for a few decades / centuries before we can say anything for sure about climate change. In the mean time, it's guessing, based upon one's faith in different theoretical constructions.

The planet's temperature drops 1C, due to the current solar magnetic cycle change. That will indicate the general climate modeling programs are fundamentally incorrect. The GCM do not model changes in planetary cloud cover. The feedback to an increase in forcing in the GCM is positive. In the physical world it is negative. The feedback is positive to create a knife edge respond to a change in forcing, which is required to create the glacial/interglacial cycle. In reality what is missing in the model is a massive external forcing function which explains why the glacial termination is very abrupt as is the start of glacial phase. The massive external forcing is why there are cyclic abrupt climate changes in the record.

Svensmark estimates the 20th century temperature rise was 75% due to solar. Svensmark's estimate is consistent with Palle's satellite cloud measurement and planetary albedo measurements using earthshine off of the moon to estimate changes in planetary albedo. The solar mechanism which caused the 20th century warming is electroscavenging. Solar wind bursts removed cloud forming ions. There is as noted in the above paper direct correlation of the changes in planetary temperature (up and down) to the Ak which is a measurement of the change in the geomagnetic field.

What you are missing is the magnitude of the temperature change due to AWG and details of the mechanism. The CO2 effect is logarithmic, the first CO2 has the greatest greenhouse effect. CO2 absorbs specific frequency bands. When CO2 has absorb all of the radiation at those frequencies it is saturated. The mechanism is different on Venus as Venus' atmosphere is as at 90 atmospheres. Under high pressure the quantum absorption frequency broaden. That is not true for the earth's atmosphere.

The lower atmosphere is saturated. CO2 absorbs all of the energy it can. Heat is carried higher in the atmosphere by convection and by the latent heat of evaporation of water.

Higher in the atmosphere there are increasing amounts of ions. The CO2 molecules transfer energy to the ions via collisions. The ions mass is different than CO2 hence frequency shifting the emitted photon such that CO2 cannot absorb it.

What is happening physically is not modeled correctly because the upper troposphere is not warming, based on satellite measurements. If additional CO2 did cause warming what would be observed is a steady increase in the trend line with planetary temperature oscillating about the trend line.

Saul

Sep20-09, 12:22 AM

http://www.atmos-chem-phys.org/5/1721/2005/acp-5-1721-2005.html

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984-2000

A decadal-scale trend in the tropical radiative energy budget has been observed recently by satellites, which however is not reproduced by climate models. In the present study, we have computed the outgoing shortwave radiation (OSR) at the top of atmosphere (TOA) at 2.5° longitude-latitude resolution and on a mean monthly basis for the 17-year period 1984-2000, by using a deterministic solar radiative transfer model and cloud climatological data from the International Satellite Cloud Climatology Project (ISCCP) D2 database. Anomaly time series for the mean monthly pixel-level OSR fluxes, as well as for the key physical parameters, were constructed.

A significant decreasing trend in OSR anomalies, starting mainly from the late 1980s, was found in tropical and subtropical regions (30° S-30° N), indicating a decadal increase in solar planetary heating equal to 1.9±0.3Wm-2/decade, reproducing well the features recorded by satellite observations, in contrast to climate model results. This increase in solar planetary heating, however, is accompanied by a similar increase in planetary cooling, due to increased outgoing longwave radiation, so that there is no change in net radiation. The model computed OSR trend is in good agreement with the corresponding linear decadal decrease of 2.5±0.4Wm-2/decade in tropical mean OSR anomalies derived from ERBE S-10N non-scanner data (edition 2). An attempt was made to identify the physical processes responsible for the decreasing trend in tropical mean OSR.

A detailed correlation analysis using pixel-level anomalies of model computed OSR flux and ISCCP cloud cover over the entire tropical and subtropical region (30° S-30° N), gave a correlation coefficient of 0.79, indicating that decreasing cloud cover is the main reason for the tropical OSR trend. According to the ISCCP-D2 data derived from the combined visible/infrared (VIS/IR) analysis, the tropical cloud cover has decreased by 6.6±0.2% per decade, in relative terms.

A detailed analysis of the inter-annual and long-term variability of the various parameters determining the OSR at TOA, has shown that the most important contribution to the observed OSR trend comes from a decrease in low-level cloud cover over the period 1984-2000, followed by decreases in middle and high-level cloud cover. Note, however, that there still remain some uncertainties associated with the existence and magnitude of trends in ISCCP-D2 cloud amounts. Opposite but small trends are introduced by increases in cloud scattering optical depth of low and middle clouds.

vanesch

Sep20-09, 12:39 AM

What you are missing is the magnitude of the temperature change due to AWG and details of the mechanism. The CO2 effect is logarithmic, the first CO2 has the greatest greenhouse effect. CO2 absorbs specific frequency bands. When CO2 has absorb all of the radiation at those frequencies it is saturated.

That is a very elementary misunderstanding of the greenhouse effect, you know. When CO2 absorbs, it also emits thermal radiation. It is unfortunate that the popular explanation of the greenhouse effect concentrates on "absorption" by greenhouse gasses. They absorb, and they re-radiate. However, they re-radiate according to the temperature of the air where they are. A layer of CO2 that is at the same temperature than the surface has strictly no effect on the thermal radiation emanating from that surface, as it will emit exactly as much as it will absorb. It is only because the "last layer" is at a lower temperature than the "emitting surface" that there *seems to be* a net absorption.

The lower atmosphere is saturated. CO2 absorbs all of the energy it can. Heat is carried higher in the atmosphere by convection and by the latent heat of evaporation of water.

Indeed, but what counts is what is re-emitted, and hence, at what altitude (and hence at what temperature) that "last emitting layer" is. As such, the fact that there is total absorption (several times over) of certain lines doesn't matter, because it also means that there is re-emission. More (evenly distributed) absorption gas simply means that the "last emitting layer" is higher up, and hence colder.

If you would have a thick layer of totally black gas, 50 meters thick, hovering over the earth's surface, that wouldn't cause any greenhouse effect at all, because that layer of gas (at the same temperature as the surface) would absorb all of the surface's radiation, but would also emit exactly the same radiation upward.

vanesch

Sep20-09, 12:46 AM

The planet's temperature drops 1C, due to the current solar magnetic cycle change. That will indicate the general climate modeling programs are fundamentally incorrect. The GCM do not model changes in planetary cloud cover. The feedback to an increase in forcing in the GCM is positive. In the physical world it is negative. The feedback is positive to create a knife edge respond to a change in forcing, which is required to create the glacial/interglacial cycle. In reality what is missing in the model is a massive external forcing function which explains why the glacial termination is very abrupt as is the start of glacial phase. The massive external forcing is why there are cyclic abrupt climate changes in the record.

This is possible. I hope - I have no idea - that the feedback for clouds is NOT based upon paleo climate data. In fact, I hope that none of the climate modeling uses paleo climate data AT ALL, but have models based upon observed behavior, or preferentially first principles. Maybe someone knowledgeable about this could comment here, whether paleo data are actually USED in the setup of climate models.

In the case that no paleo data are used to model any climate, it might be, or it might not be, that some external forcing is missing. I can't comment on that. But it would *still* mean that, in as much as the model is correct, the temperature with the forcing is higher with extra CO2 than without (even if the external forcing makes temperatures go down).

In other words, if the external forcing imposes, say, a 6 C decrease of temperature "as is", it would mean that with human CO2, this will then be a decrease of, say, only 4 or 5 C. That's still AGW. It is in that case just not the dominant forcing. But it is then still there.

sylas

Sep20-09, 03:57 AM

This is possible. I hope - I have no idea - that the feedback for clouds is NOT based upon paleo climate data. In fact, I hope that none of the climate modeling uses paleo climate data AT ALL, but have models based upon observed behavior, or preferentially first principles. Maybe someone knowledgeable about this could comment here, whether paleo data are actually USED in the setup of climate models.

Climate models are used in paleoclimate studies, both as a way of checking the model and as a way of testing hypotheses about causes and effect in climate in the past.

The best actual checks for a model are (IMO) with historical climate events; but checks of earlier times have value as well.

There a quite a large number of projects in which different climate models are compared to each other and to data for some time period or region, and there are lengthy reports available in the literature. See, for example, the Program for Climate Model Diagnosis and Intercomparison (http://www-pcmdi.llnl.gov/about/index.php) (PCMDI). This is mainly using comparisons over the last century.

With respect to paleoclimate studies, see the Paleoclimate Modelling Intercomparison Project (http://pmip.lsce.ipsl.fr/) (PMIP) and Paleoclimate Modelling Intercomparison Project Phase II (http://pmip2.lsce.ipsl.fr/) (PMIP2).

I don't know what you mean by a climate model "using paleo climate data". Models don't use climate data for the model itself. The model is basically a representation of the physics of energy flow and so on. You use data as input to a model.

In the case that no paleo data are used to model any climate, it might be, or it might not be, that some external forcing is missing. I can't comment on that.

It is always the case the there may be external forcings that are overlooked. It gets pretty implausible in the present that there's a monster forcing no-one has noticed, but hey.

You don't need climate models to show that CO2 has a significant effect in the present. The thread Estimating the impact of CO2 on global mean temperature explains how this is done. The forcing from CO2 is not based on climate models.

Of course knowing that carbon dioxide is significant says nothing at all about the magnitude of contributions from other less well understood forcings. Also, even assuming a particular set of forcings, the magnitude of the climate response is still uncertain. This depends on climate sensitivity and feedback processes for which there remains considerably uncertainty.

I'm not proposing to get into debates in this thread; the irony of that would be too overwhelming. I'm just giving the links for climate model intercomparisons with each other and with climate data past and present; and a pointer to the thread where the specifics of the CO2 impact is discussed in more detail.

Cheers -- sylas

vanesch

Sep20-09, 05:09 AM

Climate models are used in paleoclimate studies, both as a way of checking the model and as a way of testing hypotheses about causes and effect in climate in the past.

The question was the other way around: are paleo climate data used in the models themselves, to set them up ? For instance, are paleo climate data used to estimate feedback coefficients which are then plugged into climate models ;
or is it rather the other way around (as you seem to say): are paleo data used as independent TEST SET against which to test a particular model ?
The latter would be great, the former, rather risky.

I don't know what you mean by a climate model "using paleo climate data". Models don't use climate data for the model itself. The model is basically a representation of the physics of energy flow and so on. You use data as input to a model.

Yes, that's my question. Does one *need* paleo data, say, in some kind of neural network fit, to establish a certain kind of response, or are these models "first principles" models, using physics, chemistry and knowledge from specific fields to calculate responses ?

Because it seems that certain people here think that climate models are *inspired* by paleo data in order to predict certain quantities. If that's the case, I would find that indeed somewhat dubious.

Of course knowing that carbon dioxide is significant says nothing at all about the magnitude of contributions from other less well understood forcings. Also, even assuming a particular set of forcings, the magnitude of the climate response is still uncertain. This depends on climate sensitivity and feedback processes for which there remains considerably uncertainty.

I agree. That's what I wanted to point out: if one or other other forcing pushes us in a cooling, that by itself doesn't say anything about any AGW.

sylas

Sep20-09, 05:46 AM

The question was the other way around: are paleo climate data used in the models themselves, to set them up ? For instance, are paleo climate data used to estimate feedback coefficients which are then plugged into climate models ;
or is it rather the other way around (as you seem to say): are paleo data used as independent TEST SET against which to test a particular model ?

Climate models don't have feedback co-efficients.

Climate models are just representations of the physics of all the processes involved, and so within the model you have humidity and cloud and so on, and the effects of those is a feedback within the model, just like they are feedbacks in the real climate system. A model works piece by piece over the whole globe, and conditions can be quite different in different areas. You can estimate the feedbacks in a model in various ways, particularly because you can do many repeat experiments and artificially hold various aspects fixed. But there's no parameter or input or anything of the kind corresponding to a feedback value that you can enter into a model.

So it's not even possible to use paleo data as input to the model in the way you are asking about. Paleo data is used for test sets.

If you read through the papers on feedback estimation, you can get a good idea of how models and feedback parameters are related. There's a fair bit of hard work involved to try and estimate feedback parameters from a model. The number you get is a kind of diagnostic description of how the model behaves, not a value that you can supply to control it. You certainly can't just read them straight off the model itself.

For more specifics, read Appendix B of Bony et al (2006), which is: "How Are Global Radiative Feedbacks Diagnosed in GCMs?".
Bony, S., et al (2006) "How Well Do We Understand and Evaluate Climate Change Feedback Processes?" (ftp://eos.atmos.washington.edu/pub/breth/papers/2006/Bony_etal_feedbacks.pdf), in Journal of Climate, Vol 19, 1 Aug 2006, pp 3445-3482.

Yes, that's my question. Does one *need* paleo data, say, in some kind of neural network fit, to establish a certain kind of response, or are these models "first principles" models, using physics, chemistry and knowledge from specific fields to calculate responses ?

Because it seems that certain people here think that climate models are *inspired* by paleo data in order to predict certain quantities. If that's the case, I would find that indeed somewhat dubious.

I would find it very dubious also. But that's not how they do it. You don't need any data at all, until you get to testing the model. The model itself is just a representation of the physics of air and water and circulation and evaporation and so on.

I agree. That's what I wanted to point out: if one or other other forcing pushes us in a cooling, that by itself doesn't say anything about any AGW.

Quite so.

Cheers -- sylas

Saul

Sep20-09, 10:05 AM

That is a very elementary misunderstanding of the greenhouse effect, you know. When CO2 absorbs, it also emits thermal radiation. It is unfortunate that the popular explanation of the greenhouse effect concentrates on "absorption" by greenhouse gasses. They absorb, and they re-radiate. However, they re-radiate according to the temperature of the air where they are. A layer of CO2 that is at the same temperature than the surface has strictly no effect on the thermal radiation emanating from that surface, as it will emit exactly as much as it will absorb. It is only because the "last layer" is at a lower temperature than the "emitting surface" that there *seems to be* a net absorption.

Indeed, but what counts is what is re-emitted, and hence, at what altitude (and hence at what temperature) that "last emitting layer" is. As such, the fact that there is total absorption (several times over) of certain lines doesn't matter, because it also means that there is re-emission. More (evenly distributed) absorption gas simply means that the "last emitting layer" is higher up, and hence colder.

If you would have a thick layer of totally black gas, 50 meters thick, hovering over the earth's surface, that wouldn't cause any greenhouse effect at all, because that layer of gas (at the same temperature as the surface) would absorb all of the surface's radiation, but would also emit exactly the same radiation upward.

My point is that CO2 only absorbs and emits specific frequencies. If the photons are frequency shifted off of those frequencies CO2 no longer is a factor. Do you understand that point?

Does any in the forum disagree with that assertion?

This is a good paper that describes the basic physics of greenhouse gases.

http://www.warwickhughes.com/papers/barrett_ee05.pdf

Greenhouse molecules, their spectra and function in the atmosphere by Jack Barrett

Comment:
In the above you state something about absorption and emission which appears to not be relavent to my point.

Saul

Sep20-09, 10:21 AM

sylas

Sep20-09, 10:58 AM

My point is that CO2 only absorbs and emits specific frequencies. If the photons are frequency shifted off of those frequency CO2 no longer is a factor. Do you understand that point?

Does any in the forum disagree with that assertion?

This is a subject on which you were mistaken in past discussions, and it seems you still don't understand it. CO2 is ALWAYS a factor at any conceivable concentration up to many many times more than we are ever likely to see. There are always still frequencies of light that are on the shoulder of the main saturated absorption band. As CO2 concentrations increase, the width of the saturated band increases. There is more absorption, because there are more frequencies that move from being weakly absorbed in the atmosphere to being strongly absorbed. The approximately logarithmic relation between concentrations and forcing continues smoothly up to very high densities of CO2 within the atmosphere.

I first explained this for you back in April, in msg #3 of thread "Estimating the impact of CO2 on global mean temperature".

I have subsequently given another account of the relevant physics, with reference to an easily accessible text book on "Principles of Planetary Climate", in msg #15 of thread "Rising Carbon Dioxide Levels Don’t Increase Earth’s Temperature". Note especially the diagram in that post showing the spectrum of emitted radiation for different CO2 concentrations. Note that the width of the band of absorbed frequencies is increasing, and that increasing CO2 continues to be a factor even up past an atmosphere of 1% CO2, at which point some additional bands start to take hold and enhance the impact even more.

This is the aspect of the underlying and well established physics of light absorption in a gas which is not understood by those who think that there is some level of concentration beyond which additional CO2 has negligible further effect. The fact of the matter is that the absorption of light at a given frequency is not a simple case of yes/no, but varies continuously in strength, so that as concentrations increase, there is more and more of the spectrum that becomes strongly absorbed.

Sylas

PS. I continue to find it ridiculous that in this thread, of all threads, we end up going over the same tired old topics, refuting the same misconceptions as before. I feel a bit guilty participating in this way, but given the direct question, I succumbed to temptation and gave the explanation.

Saul: don't make up self serving statements about why I might ignore a posting. Speak for yourself; do not try to speak for me or my choices. You do not know why I might respond to one post or another, and in this case you are flatly wrong about why I am ignoring most of your posts here.

I'll continue to try and avoid using this thread to just debate climate with everyone taking the same perspective as they have ever done. The topic, as I understand it, was about being able to argue for the OTHER person's perspective. I'm not sure that this is all that useful, frankly, but certainly it is very useful to actually understand the arguments being made on their own merits. Being able to repeat the argument is a rather futile exercise if the argument takes for granted some premise that is incorrect.

The greatest benefits of being able to repeat the argument for a position you don't hold yourself is (IMO) when the argument is sufficiently sensible. The restriction of the guidelines to consider arguments that have been made in peer reviewed literature is a good way to help getting to such arguments.

vanesch

Sep20-09, 11:10 AM

My point is that CO2 only absorbs and emits specific frequencies. If the photons are frequency shifted off of those frequencies CO2 no longer is a factor. Do you understand that point?

First of all, CO2 doesn't absorb and emit at just specific frequencies, because there is Doppler and collision broadening, which is dependent on temperature and pressure, so we have finite absorption bands. I don't know if this is part of what you consider "specific frequencies".

Next, there are very few "wavelength-shifting" phenomena in the atmosphere, which operate between specific levels (like people sometimes try to do in scintillators). What you have is that absorbed radiation goes into the "heat bath" of the specific layer of gas (just as any other heat, like that brought by convection, latent heat transport, or even conduction), and the heat bath induces the gas to radiate black body radiation modulated with its overall emissivity.

What counts is the "final radiator" which can put its radiation into space. Not what happens with essentially isothermal low-lying layers.

vanesch

Sep20-09, 11:18 AM

The point is if the planet is about to abruptly cool, CO2 sequestration, CO2 caps, and CO2 trading have no scientific purpose.

There is not a single instance in which CO2 sequestration, CO2 caps, and CO2 trading would have any scientific purpose, in any case, except in the case where we want to experiment with first rising, and then lowering, CO2 levels, to see how the earth reacts.

As I said already several times, whether AGW is "good" or "bad", whether one "should do something about it or not", and the like, are no part in the scientific debate about whether AGW exists, and if it exists, how strong it is.

You wouldn't react that way if the scientific debate were to know whether volcanic eruptions on Titan change the surface temperature, and by how much, would you ? Well, the scientific AGW debate is the same. It is totally distinct from any political, societal, or economical consideration in itself. It just asks a question: by how much, if any, will the earth be warmer when there are CO2 emissions of such and such a kind, as compared to when this is not the case, all else equal. The attempt to an answer to that question, and the argumentation for it, is what the scientific AGW debate is about. And that's it.

vanesch

Sep20-09, 11:22 AM

The topic, as I understand it, was about being able to argue for the OTHER person's perspective. I'm not sure that this is all that useful, frankly, but certainly it is very useful to actually understand the arguments being made on their own merits. Being able to repeat the argument is a rather futile exercise if the argument takes for granted some premise that is incorrect.

I think it is inspired by Feynman's statement, that one should try by all means to prove oneself wrong, if one is doing science. The highest form of skepticism should be towards one's own ideas.

Saul

Sep20-09, 12:25 PM

This is a subject on which you were mistaken in past discussions, and it seems you still don't understand it. CO2 is ALWAYS a factor at any conceivable concentration up to many many times more than we are ever likely to see. There are always still frequencies of light that are on the shoulder of the main saturated absorption band. As CO2 concentrations increase, the width of the saturated band increases. There is more absorption, because there are more frequencies that move from being weakly absorbed in the atmosphere to being strongly absorbed. The approximately logarithmic relation between concentrations and forcing continues smoothly up to very high densities of CO2 within the atmosphere.

I first explained this for you back in April, in msg #3 of thread "Estimating the impact of CO2 on global mean temperature".

I have subsequently given another account of the relevant physics, with reference to an easily accessible text book on "Principles of Planetary Climate", in msg #15 of thread "Rising Carbon Dioxide Levels Don’t Increase Earth’s Temperature". Note especially the diagram in that post showing the spectrum of emitted radiation for different CO2 concentrations. Note that the width of the band of absorbed frequencies is increasing, and that increasing CO2 continues to be a factor even up past an atmosphere of 1% CO2, at which point some additional bands start to take hold and enhance the impact even more.

This is the aspect of the underlying and well established physics of light absorption in a gas which is not understood by those who think that there is some level of concentration beyond which additional CO2 has negligible further effect. The fact of the matter is that the absorption of light at a given frequency is not a simple case of yes/no, but varies continuously in strength, so that as concentrations increase, there is more and more of the spectrum that becomes strongly absorbed.

Sylas

PS. I continue to find it ridiculous that in this thread, of all threads, we end up going over the same tired old topics, refuting the same misconceptions as before. I feel a bit guilty participating in this way, but given the direct question, I succumbed to temptation and gave the explanation.

Saul: don't make up self serving statements about why I might ignore a posting. Speak for yourself; do not try to speak for me or my choices. You do not know why I might respond to one post or another, and in this case you are flatly wrong about why I am ignoring most of your posts here.

I'll continue to try and avoid using this thread to just debate climate with everyone taking the same perspective as they have ever done. The topic, as I understand it, was about being able to argue for the OTHER person's perspective. I'm not sure that this is all that useful, frankly, but certainly it is very useful to actually understand the arguments being made on their own merits. Being able to repeat the argument is a rather futile exercise if the argument takes for granted some premise that is incorrect.

The greatest benefits of being able to repeat the argument for a position you don't hold yourself is (IMO) when the argument is sufficiently sensible. The restriction of the guidelines to consider arguments that have been made in peer reviewed literature is a good way to help getting to such arguments.

sylas,

I am saying the first CO2 added has the greatest impact on global warming. Additional CO2 added has less impact. The physical reason why that statement is correct is that CO2 only absorbs and emits specific band widths.

http://www.warwickhughes.com/papers/barrett_ee05.pdf

The effect of adding additional CO2 to the atmosphere is logarithmic. The first 30% added has a significantly greater affect on planetary temperature than the last 30% added. (280 ppm to 560 ppm.)

Do you disagree with that statement? Do you have a paper that disputes that statement? Do you have a paper that refutes this paper?

Greenhouse molecules, their spectra and function in the atmosphere by Jack Barrett

http://www.warwickhughes.com/papers/barrett_ee05.pdf

Please do not use ad hominem. It serves no purpose. This is a scientific forum not a debating forum. Compare the two different scientific positions rather than trying to win a debate. In a debate, ad hominem is acceptable if one can get away with ad hominem. In a debate the objective is to win the debate rather than to understand a scientific problem.

A scientific discussion/debate must handle uncertainty. It is not absolutes.The process of science is the creation and comparison of hypotheses. For science to progress hypotheses must be challenged and discussed. The title of this thread is devil's advocate.

I have provided papers and logic to support a scientific position. I have provided data from papers concerning cyclic abrupt climate change. In the past cyclic abrupt climate change has correlated with cosmogenic isotope changes. I presented a paper that shows planetary clouds have decreased in the 20th century. I provided a paper that shows planetary temperature is directly correlated with solar wind bursts in the 20th century. I have provided papers that explain electroscavenging which is the hypothesized mechanism by which the solar wind burst modulate planetary cloud cover.

The question which we are discussing is the magnitude of the 20th century warming that was due to CO2 as opposed to changes in planetary cloud cover. Your ad hominem is that I have not provided papers to support a position. Or that I do not understand the physics. Or that all scientists agree with your position.

Note I am presenting a scientific hypothesis. I do not own it. It is not my baby, my child, and so forth on. I have no emotional attachment to it. Note it is a scientific position.

Try to think of the two scientific positions in a hypothetical manner. What are the implications of the two hypotheses? If this were true than that what would we expect to happen in the future. Does new observational data support or refute the position? Do new papers support or refute the scientific position?

Please note also that I have found and presented new papers that support the cloud hypothesis. The archeomagnetic jerk paper. The paper that shows anomalously high solar wind bursts during this solar cycle minimum. I am not simply stating the same thing over again. I come back to the forum with new information.

I find this subject interesting because the scientific issues are not resolved. Scientists do not know what causes abrupt climate change and the glacial/interglacial cycle. I find this discussion interesting also because the sun is moving abruptly to a peculiar solar minimum. Solar physicists do not understand what is happening to sun currently and do not know what will happen next. Solar physicists do not know what is limits of solar CME magnitude.

sylas

Sep20-09, 12:51 PM

The effect of adding additional CO2 to the atmosphere is logarithmic. The first 30% added has a significantly greater affect on planetary temperature than the last 30% added. (280 ppm to 560 ppm.)

Yes. The forcing is about 3.7 W/m2 for each doubling of concentration.

This is much better than the previous statement you gave, which spoke of "CO2 is no longer a factor". The full sentence which you used in the previous post was "If the photons are frequency shifted off of those frequencies CO2 no longer is a factor."

That's incoherent, so it was impossible to agree or disagree with the sentence as you phrased it in the earlier post. "the photons are frequency shifted off those frequencies"? Who knows what this might mean? What I do know is that a few months ago you were saying:
It is not a fact that a doubling of CO2 will increase forcing by 3.71 W/m^2. Why do you make that statement?

The consensus is the lower atmosphere is saturated from the standpoint of direct heating effects of CO2. Adding more CO2 to the lower atmosphere will not result in higher surface temperatures.

This was, of course, completely incorrect. When you said just now "CO2 is no longer a factor", I confess that I had thought you were still thinking that there is a condition of "saturation" which means adding more CO2 does not raise temperatures any further. There's nothing in the older discussion to suggest you had come to understand why you do get continuing increases in temperature with continuing increases in concentration, with a logarithmic relation of a certain impact per doubling. I am sincerely glad to hear we are now on the same page with this, and that you no longer hold to the view you had four months ago. You deserve full credit for that -- it shows that you ARE learning new things, and that is good. Truly.

It is a bit amusing, however, to see you demand whether I can refute your position when it is what I had to explain to you four months ago.

Please do not use ad hominem.

I did not use any ad hominem in that post at all.

PS. I do know you have come back to the forum with new material, and you're engaging that in some other threads. Good for you, really. I won't join in all those threads, because it's not all my main interest. And I don't want to take up climate debates here. This thread is for a meta-discussion on the nature of discussion methods for engaging conflicting views. It's not for going straight into another round of climate debates. I am now returning to that proper focus for this thread.

Over and out -- sylas

sylas

Sep20-09, 01:50 PM

I think it is inspired by Feynman's statement, that one should try by all means to prove oneself wrong, if one is doing science. The highest form of skepticism should be towards one's own ideas.

I agree.

Doing science vs learning science

In physicsforums, a lot of what we do is basic education. People come with questions about some tricky subject, be it cosmology, relativity, climate, quantum mechanics, whatever, and discussion tries to answer those questions.

This is a worthwhile endeavor, but in most cases it has nothing much to do with trying to prove oneself wrong.

In my opinion, a large part of the confusion over climate is simply outright error about what is really quite basic physics or statistics or whatever. One of the things I would like to see at physicsforums is some basic educational threads on background details or concepts that people may be confused about, so that those who are interested are on more solid ground for starting to look at the harder and open questions. I've tried to put up some.

But that project has nothing much to do with the laudable exercise of self-criticism. It is rather about the also laudable exercise of science education, with a transfer of knowledge from people who have more background understanding to others who have less.

Most of us here are able to give useful instruction in some topics, and have other topics where we are seeking to learn. Doing science is a good way to learn science; but in most cases we are exploring a well beaten trail blazed by those who did the same science before us.

Open questions vs popular misconceptions

The quality of arguments relating to climate and AGW varies enormously.

We swiftly get straight into deep water, however, because people don't agree about which questions are actually those that are genuinely open; and there's no general recognition of an acceptable authority. Many people seem to be quite sure that the whole idea of global warming is some kind of hoax. We get into all kinds of secondary matters of why people argue for something or other, or what their history or funding is, or how important it is, and so on; this (as you point out) just distracts from the business of learning about the science.

We are not doing cutting edge science here. There are members at physicsforums who are actively involved in cutting edge science, but most of the discussion here is trying to learn about the science being done by others.

In the process of learning, we also learn about open questions. We aren't going to resolve those questions here in physicsforums! But we can learn about them. In particular, we can get a better idea of what questions really are wide open, and what is reasonably solid and used by working scientists as a foundation for exploring into the unknown.

The physicsforums context: physics as practiced by the scientific community

The guidelines (http://www.physicsforums.com/showthread.php?t=5374) for physicsforums single out as a focus "the current status of physics as practiced by the scientific community". I think climate is primarily a field within physics; dealing with thermodynamics, atmospheric physics, fluid dynamics, energy and temperature, and so on.

Physicsforums also deals with open questions. From the guidelines (http://www.physicsforums.com/showthread.php?t=5374) again:
There are many open questions in physics, and we welcome discussion on those subjects provided the discussion remains intellectually sound. It is against our Posting Guidelines to discuss, in most of the PF forums or in blogs, new or non-mainstream theories or ideas that have not been published in professional peer-reviewed journals or are not part of current professional mainstream scientific discussion.

In climate, there are many open questions, relating to sensitivity, cloud effects, paleoclimate, approximations in modeling, the carbon cycle, and on, and on. We aren't going to resolve them, but understanding the credible alternatives is well worthwhile.

There are also a lot of questions which are not actually intellectually sound open questions at all, but simply misunderstandings or even outright crackpottery. There's a lot that is said outside the professional mainstream which has been enthusiastically passed around in the public domain as being of equal standing to genuine science. In some respects, a lot of this public debate (not all of it!) bears a significant similarity to the whole "intelligent design" movement.

Physicsforums guidelines give a convenient way to strip out most of the rubbish, and they have special force in the Earth subforum. We simply stick to claims that have been published in the peer reviewed scientific literature. (And, like it or not, the journal "Energy and Environment" does not qualify. See this post from an Earth subforum mentor.)

There are sometimes good papers published outside the peer reviewed literature. But if the claims made are at all credible, then you should be able to find them in the peer reviewed literature as well. Apart from that, there is a Independent Research subforum (http://www.physicsforums.com/forumdisplay.php?f=146), with its own Rules for submission in Independent Research.

Don't let's fall into the mistake of "journalistic balance", in which we simply presume all voices are equally worthwhile for study and serious consideration. Understanding all sides of an open question is good; but not all the questions or challenges being raised are actually open questions with two sides of comparable standing.

Cheers -- sylas

Saul

Sep20-09, 04:12 PM

This is a fascinating forum, and these climate discussions are very interesting and educational. I couldn't help but notice however that it seems posters tend to line up along sides on the issue of AGW (or perhaps the degree to which they are skeptical of the consensus). I think it would be interesting to see people play devil's advocate and argue for the other position, or rather acknoweldge data that does not support their view (on both sides).

Galtheeth,

Climate discussion for some strange reason seems to be an emotional subject.

I agree that scientific discussions should compare one hypothesis to another. What does the hypotheses predict? What do the observations indicate? It should be noted that papers are still begin written and published concerning planetary temperature change.

This topic is it not settled scientifically. There is good quality data and published papers that challenge the base AWG hypothesis that doubling CO2 will result in planetary warming of 3C to 5C.

There has been a recent paper published warning of a decade or two of cooling which seems odd. Typically when there is disagreement between observations and theory, something is incorrect with the base assumptions.

It is extraordinary the sun is currently moving toward a peculiar minimum. As I have noted there have been a series of abrupt cooling events that correlate with cosmogenic isotope changes. Everyone has heard of the "Little Ice Age". There is in the paleo climatic record a cyclic series of abrupt cooling events.

Skyhunter

Sep20-09, 05:51 PM

It is extraordinary the sun is currently moving toward a peculiar minimum. As I have noted there have been a series of abrupt cooling events that correlate with cosmogenic isotope changes. Everyone has heard of the "Little Ice Ages". There is in the paleo climatic record a cyclic series of abrupt cooling events.

What do you consider an abrupt cooling?

You posted a graphic of the Antarctic ice cores that show the glacial/interglacial cycles that are correlated to the Milankovic cycles. These cooling and warming events occur over centuries and indicate strong feedbacks to long term forcings. The solar constant does not vary enough to account for the difference in temperature from a glacial to interglacial period.

The Sun is currently at a minimum as cycle 23 ends and cycle 24 begins. Expect higher solar intensity for the next five years.

Saul

Sep20-09, 07:20 PM

What do you consider an abrupt cooling?

You posted a graphic of the Antarctic ice cores that show the glacial/interglacial cycles that are correlated to the Milankovic cycles. These cooling and warming events occur over centuries and indicate strong feedbacks to long term forcings. The solar constant does not vary enough to account for the difference in temperature from a glacial to interglacial period.

The Sun is currently at a minimum as cycle 23 ends and cycle 24 begins. Expect higher solar intensity for the next five years.

The 8200 BP present event was a 2C degree cooling event in the Northern Hemisphere.

There is evidence of an abrupt change of cosmogenic isotopes that occurs concurrently with each of the past abrupt cooling events. The mechanism is not as you note a reduction in TSI. The sun does not get warmer or colder, so the explanation for abrupt planetary cooling is not a reduction in TSI.

One possible explanation is an increase in GCR due to a reduction in the heliosphere which in turn causes an increase in planetary clouds. That is a possible explanation for some of the cooling events.

It seems the sun is involved with what ever the forcing mechanism is. As I noted there have been a recent set of papers published noting a reduction in the geomagnetic field at the same time as the abrupt cooling.

Comment:
I have been following this solar minimum. It appears to be a interruption to the solar magnetic cycle rather than the cycle slow down. The magnetic field of new sunspots that are produced has been decreasing linearly with time. The typical magnetic field strength of a sun spot was around 3000 gauss before this change. It is calculated the sunspot requires a minimum field strength of 2000 gauss to survive the trip from the bottom of solar convection zone through the convection zone. The sunspots that are produce are smaller and last only a day or two as compared to up to a week for a normal sunspot. The last sunspot only survived a few hours.

As this phenomena has never been observed before it is not clear what specifically is happening. It is also not clear how the solar cycle restarts after an interruption.

http://www.ingentaconnect.com/content/klu/367/2008/00000028/00000003/00000095

Evidence for the 8,200 a b.p. cooling event in the middle Okinawa Trough

Based on new and existing data on oxygen isotopes, alkenone-surface seawater temperature trends, planktonic foraminifers, lithology, and clay mineral composition of piston cores, a distinct cooling event has been identified around 8,200 cal a b.p. in the middle Okinawa Trough, northwest Pacific. This corresponds to the 8,200 a b.p. cooling event recorded in many places of the Northern Hemisphere. During this event, the local temperature decreased by 1°C, and the δ18O value increased by 0.6‰. A strengthened Asian winter monsoon is the most probable cause for this event, which thus adds further credibility to the contention that we are dealing here with a global phenomenon.

http://adsabs.harvard.edu/abs/2005Natur.434..975R

Centennial-scale climate cooling with a sudden cold event around 8,200 years ago

The extent of climate variability during the current interglacial period, the Holocene, is still debated. Temperature records derived from central Greenland ice cores show one significant temperature anomaly between 8,200 and 8,100 years ago, which is often attributed to a meltwater outflow into the North Atlantic Ocean and a slowdown of North Atlantic Deep Water formation--this anomaly provides an opportunity to study such processes with relevance to present-day freshening of the North Atlantic. Anomalies in climate proxy records from locations around the globe are often correlated with this sharp event in Greenland. But the anomalies in many of these records span 400 to 600 years, start from about 8,600 years ago and form part of a repeating pattern within the Holocene. More sudden climate changes around 8,200 years ago appear superimposed on this longer-term cooling. The compounded nature of the signals implies that far-field climate anomalies around 8,200 years ago cannot be used in a straightforward manner to assess the impact of a slowdown of North Atlantic Deep Water formation, and the geographical extent of the rapid cooling event 8,200 years ago remains to be determined.

http://www.essc.psu.edu/essc_web/seminars/spring2006/Mar1/Bond%20et%20al%202001.pdf

Persistent Solar Influence on North Atlantic Climate During the Holocene

Gerard Bond, Bernd Kromer, Juerg Beer, Raimund Muscheler, Michael N. Evans, William Showers, Sharon Hoffmann,Rusty Lotti-Bond,1 Irka Hajdas, Georges Bonani

Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic 1500-year cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally.

http://geology.geoscienceworld.org/cgi/content/abstract/30/5/455

Widespread evidence of 1500 yr climate variability in North America during the past 14,000 yr

There is debate concerning the spatial extent and magnitude of the recently identified 1500 yr climate oscillation. Existing evidence is largely restricted to the North Atlantic and adjacent landmasses. The spatial extent, magnitude, and effects of these climate variations within the terrestrial environment during the Holocene have not been established. We show that millennial-scale climate variability caused changes in vegetation communities across all of North America with a periodicity of 1650 ± 500 yr during the past 14 000 calendar years (cal yr). Times of major transitions identified in pollen records occurred at 600, 1650, 2850, 4030, 6700, 8100, 10 190, 12 900, and 13 800 cal yr B.P., consistent with ice and marine records. We suggest that North Atlantic millennial-scale climate variability is associated with rearrangements of the atmospheric circulation with far-reaching influences on the climate.

Saul

Sep20-09, 08:54 PM

This is solar data the indicates something unusual is occurring with the sun.

http://science.nasa.gov/headlines/y2009/03sep_sunspots.htm

Penn's colleague Bill Livingston of the NSO has been measuring the magnetic fields of sunspots for the past 17 years, and he has found a remarkable trend. Sunspot magnetism is on the decline:

"Sunspot magnetic fields are dropping by about 50 gauss per year," says Penn. "If we extrapolate this trend into the future, sunspots could completely vanish around the year 2015."

"According to our measurements, sunspots seem to form only if the magnetic field is stronger than about 1500 gauss," says Livingston. "If the current trend continues, we'll hit that threshold in the near future, and solar magnetic fields would become too weak to form sunspots."

(my comment: Eugene Parker’s calculation was that a minimum field strength of 2000 gauss is required for a sunspot to survive the turbulence in the convection zone. This data however shows sunspots with a field of strength minimum of 1500 gauss. Base on Penn and Livingstone’s data, there will be no more sunspots sometime late 2012. They state 2015 in the article but the graph seems to indicate around 2012.)

"This work has caused a sensation in the field of solar physics," comments NASA sunspot expert David Hathaway, who is not directly involved in the research. "It's controversial stuff."

Penn himself wonders about these points. "Our technique is relatively new and the data stretches back in time only 17 years. We could be observing a temporary downturn that will reverse itself."

Are Sunspots Different During This Solar Minimum?

http://www.leif.org/EOS/2009EO300001.pdf

Saul

Sep20-09, 09:15 PM

This is further from the solar paper and a link to a sunspot summary.

As that solar wind paper noted solar wind bursts increased anomalously by a factor of three during the end of cycle 24, as compared to past solar cycles. The solar wind bursts have now started to abate. Based on the mechanisms it is expected this winter should be unusually cold.

But something is unusual about the current sunspot cycle. The current solar minimum has been unusually long, and with more than 670 days without sunspots through June 2009, the number of spotless days has not been equaled since 1933 (see ) The solar wind is http://users.telenet.be/j.janssens/Spotless/Spotless.html reported to be in a uniquely low energy state since space measurements began nearly 40 years ago [Fisk and Zhao, 2009].

Yet although the Sun’s magnetic polarity has reversed and the new solar cycle has been detected, most of the new cycle’s spots have been tiny “pores” without penumbrae (see Figure 1); in fact, nearly all of these features are seen only on flux magnetograms and are difficult to detect on whitelight images.

What could be happening? Clues can be found in the McMath- Pierce’s infrared magnetic measurements, which are able to calculate the total magnetic field strength directly (not the flux) in the umbrae. These measurements also have the advantage of observing the sunspots in the infrared spectrum, which guarantees the reduction ...

Xnn

Sep20-09, 09:15 PM

What sun spots?

The current minimum is the greatest minimum since about 1911, which globally was a very cool period unlike our current situation.

Skyhunter

Sep21-09, 07:35 AM

Climate until recently is closely correlated with solar activity. No surprise since aside from orbital and volcanic forcings, it has been the strongest variable. That fact has no bearing on the radiative forcing of CO2.

Also, the highest resolution of the proxies in the links you provided is 20 years, and generally 30 to 50 years. If the Sun is entering another Dalton or Maunder minimum then it is a good thing. It means we will have more time to stabilize atmospheric CO2.

Saul

Sep21-09, 09:50 PM

What sun spots?

The current minimum is the greatest minimum since about 1911, which globally was a very cool period unlike our current situation.

There is a reason why the planet has not cooled due to the increase GCR. GCR has increased 18%.

There is direct correlation of planetary temperature change with solar wind bursts (see the attached paper). The solar wind bursts remove the cloud forming ions that are created by galactic cosmic rays (GCR) by a process called electroscavenging. (The solar wind burst create a space charge differential in the ionosphere which creates a potential difference from the ionosphere and the surface of the earth.)

Although the sun is mostly spotless this year there has continued to be solar wind bursts produced which is masking the affects of the weak solar heliosphere. The heliosphere blocks GCR from striking the earth. The solar wind bursts are still occurring but are starting to weaken.

An observed change that accompanied the reducing of the solar wind bursts is a curious sudden weakening of the super El Nino. This winter should be anomalously cold.

http://wattsupwiththat.com/2009/09/21/jpls-patzert-its-actually-eroding-the-credibility-of-long-range-forecasters-and-climatologists/

http://www.agu.org/pubs/crossref/2009/2009JA014342.shtml

If the Sun is so quiet, why is the Earth ringing? A comparison of two solar minimum intervals.

Observations from the recent Whole Heliosphere Interval (WHI) solar minimum campaign are compared to last cycle's Whole Sun Month (WSM) to demonstrate that sunspot numbers, while providing a good measure of solar activity, do not provide sufficient information to gauge solar and heliospheric magnetic complexity and its effect at the Earth. The present solar minimum is exceptionally quiet, with sunspot numbers at their lowest in 75 years and solar wind magnetic field strength lower than ever observed. Despite, or perhaps because of, a global weakness in the heliospheric magnetic field, large near-equatorial coronal holes lingered even as the sunspots disappeared. Consequently, for the months surrounding the WHI campaign, strong, long, and recurring high-speed streams in the solar wind intercepted the Earth in contrast to the weaker and more sporadic streams that occurred around the time of last cycle's WSM campaign.

http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..969G.pdf

Once again about global warming and solar activity K. Georgieva, C. Bianchi, and B. Kirov

We show that the index commonly used for quantifying long-term changes in solar activity, the sunspot number, accounts for only one part of solar activity and using this index leads to the underestimation of the role of solar activity in the global warming in the recent decades. A more suitable index is the geomagnetic activity which reflects all solar activity, and it is highly correlated to global temperature variations in the whole period for which we have data.

In Figure 6 the long-term variations in global temperature are compared to the long-term variations in geomagnetic activity as expressed by the ak-index (Nevanlinna and Kataja 2003). The correlation between the two quantities is 0.85 with p<0.01 for the whole period studied.It could therefore be concluded that both the decreasing correlation between sunspot number and geomagnetic activity, and the deviation of the global temperature long-term trend from solar activity as expressed by sunspot index are due to the increased number of high-speed streams of solar wind on the declining phase and in the minimum of sunspot cycle in the last decades

vanesch

Sep22-09, 02:02 AM

Don't let's fall into the mistake of "journalistic balance", in which we simply presume all voices are equally worthwhile for study and serious consideration. Understanding all sides of an open question is good; but not all the questions or challenges being raised are actually open questions with two sides of comparable standing.

Well, we tend to try to establish indeed some kind of "journalistic balance", but to get it "biased" towards the scientifically sound, we are rather strict (much more so than anywhere else) on the "peer review of sources" side.

The reason for that is simple and down-to-earth: the staff at PF doesn't feel qualified enough to do so in an unanimous way. This is much less of a problem in most other forums of PF: we have quite some very knowledgeable people on board in physics, engineering, mathematics and so on. If something obviously wrong is posted there, there is very soon a consensus by "those who know" amongst staff and regular posters, and appropriate action is taken. If you know a field rather well, it is not too difficult to make the distinction between "an open question" and a "basic error".

But in earth sciences we haven't such a set of staff members, especially for the topic of AGW. So we had a few options:
- leave the earth sciences forum evolve by itself (but that's against the basic philosophy of PF)
- close it down
- impose the current policy which is a kind of "coward's moderation": discuss what you want, but have peer-reviewed sources.

This debate comes up regularly.

sylas

Sep22-09, 03:18 AM

Well, we tend to try to establish indeed some kind of "journalistic balance", but to get it "biased" towards the scientifically sound, we are rather strict (much more so than anywhere else) on the "peer review of sources" side.

This is an excellent solution, and a perfectly good resolution of the problem. It still leaves the field wide open to all the genuinely open questions on climate.

The reason for that is simple and down-to-earth: the staff at PF doesn't feel qualified enough to do so in an unanimous way. This is much less of a problem in most other forums of PF: we have quite some very knowledgeable people on board in physics, engineering, mathematics and so on. If something obviously wrong is posted there, there is very soon a consensus by "those who know" amongst staff and regular posters, and appropriate action is taken. If you know a field rather well, it is not too difficult to make the distinction between "an open question" and a "basic error".

I've heard the problem mentioned already, of a lack of a staff member with a particular expertise in climate.

It seems to me that this shouldn't be that much of a problem... and that you've collectively hit upon an ideal solution.

As you say, the reason it would be nice to have an expert available is that they would be well placed to identify straight away what arguments are disconnected from scientifically sound engagements. But you might find that the application of such expertise in this way is more trouble than it is worth. It works okay with relativity and maths and engineering, because there isn't a huge popular support for the few cranks that we get. That's not the case with climate. I am quite sure you will find that even if you had a climate expert available, even the staff would be divided on whether they were "balanced".

(And it doesn't matter which side you think has most of the cranks. Whether you accept AGW, or reject it, or are on the fence; it is still not hard to see that there is a particular problem here with unscientific argument -- whether you think it is in the IPCC or in the ranks of their critics.)

I think it is much better to have a simple clear guideline, which is a natural extension of the overall physicsforums guidelines. It is expressed without any reference to the particular claims that may not be argued.

Even if you had an expert on staff, you are still best to enforce this rule in the Earth forum, simply because there is so much more material being passed around on the subject which is not scientifically sensible, and because there are such widely divergent views amongst people interested in the subject.

On being a mentor, and being a debator

Even if you had such an expert on staff, my own suggestion (for what it is worth) is that they would be better as a participant in the Earth forum than as a mentor. I've been a moderator in other forums (evcforms.com), and a general rule was that moderators don't moderate threads in which they are involved as participants. It runs into problems with conflict of interest. If an issue turns up in a thread where a moderator is participating, then a new staff member must be called in to deal with it.

A moderator is not there to give the answers to questions, but to manage the way discussion is engaged. Having someone to give answers is great; but you don't need special moderator powers for that. The mentors here do often seem to have excellent knowledge in their own major fields of interest, and their input as experts is very welcome. But that input is distinct from acting as a moderator of the debate,

And by the way; I love the fact that you speak of "mentors" here rather than "moderators". It's a great way to look at this special role.

A mentor role in general does include giving guidance on substance, as well as conduct or rules of debate. Unfortunately, that is not going to work in a debate unless the mentor is recognized as an expert by participants; and that is going to be a particular problem in climate discussions.

Therefore you're going to have to give some enforced rulings to people who don't want them; and for that we are back to being a moderator and having a clear guideline that does not require special expertise to apply, and which someone can understand without having to accept your expertise.

But in earth sciences we haven't such a set of staff members, especially for the topic of AGW. So we had a few options:
- leave the earth sciences forum evolve by itself (but that's against the basic philosophy of PF)
- close it down
- impose the current policy which is a kind of "coward's moderation": discuss what you want, but have peer-reviewed sources.

This debate comes up regularly.

I think you've got this one nailed. The first solution is obviously wrong, and would make this forum no different to a thousand other venues. It is the second solution that is the one which is a coward's moderation.

The third is not cowardice at all. It is recognition not only of a lack of a particular expert, but of the problem that you will NEVER get anyone who is recognized as a legitimate expert by the people who want to discuss this topic. There's a huge need for improved understanding of the physical science behind climate disputes -- and again, this is a point that would be recognized by both sides, even if they might differ on who it is that needs to improve their understanding!

Cheers -- sylas

D H

Sep22-09, 06:06 AM

sylas

Sep22-09, 06:22 AM

That would be an excellent solution if the science behind AGW was not suspect. It certainly looks suspect from the outside. More importantly, it looks suspect to some very well-qualified meteorologists and climatologists. Because PF does not have a supply of meteorologists and climatologists onboard, the PF solution is, as vanesch mentioned, a bit of a cowardly solution.

Bingo. As it happens, I disagree with you... but it doesn't matter.

The whole reason for this solution is that it doesn't matter if you think it is the science behind AGW that is suspect, or the science of the critics that is suspect. In either case, the case can be found in the scientific literature, and moderators don't have to rule on the basis of choosing sides.

There are also well qualified meterologists and climatologists who think the science behind AGW is just fine. Not settled in every respect of course! There are plenty of open questions.

This is precisely why having an expert won't work. Which expert would be acceptable? The experts you are thinking of, who consider science behind AGW to be suspect? Or the ones I am thinking of, who think AGW is a well supported scientific hypothesis, confirmed to good confidence by a large amount of perfectly good scientific research and still subject to open questions in the details?

As I said previously, you will never find an expert who is acceptable to all sides -- even all sides within the staff!

You've said the science behind AGW is suspect. All I am really saying is that almost everyone can agree that there's a lot of suspect science involved... even if we disagree as to which is the suspect science!

The proper thing to do is to allow the various arguments to be considered, on all sides, and on their own merits... as long as those sides are presented in the scientific literature. That strips out a lot of really bad argument, consistent with the general physicsforums guidelines, and allows us to look at the arguments that have at least passed through the first level of check for credible scholarship. We do NOT rule on the basis of "consensus", or by some method of evaluating the "expertise" of authors, or by deciding which side the argument is on and either binning it or lauding it on that basis.

We look at the actual evidence presented, case, by case, by case.

I don't expect this process to resolve all the differences, but it sure as heck will let you learn a lot, if you are serious about looking at the arguments on their own merits. I've benefited enormously in learning about all the background physics as I've been working on this. Not just arguments for or against AGW, but about the underlying physics that lets me start to follow the details of the arguments being presented. And I'm still learning on that.

I especially disagree with you that this is "cowardly".

There's nothing cowardly about it. What would be "courageous"? To open up physicsforums to all arguments of any kind? Of course not. That would be a complete cop out. To step in and rule that one side or the other is disallowed? That would be just as bad.

So what? How do you decide... and WHO decides? You need something that lets you and I work together on this; not a ruling that rejects the experts you are thinking of or rejects the experts I am thinking of.

Cheers -- sylas

Galteeth

Sep22-09, 04:14 PM

"Physicsforums also deals with open questions. From the guidelines again:
There are many open questions in physics, and we welcome discussion on those subjects provided the discussion remains intellectually sound. It is against our Posting Guidelines to discuss, in most of the PF forums or in blogs, new or non-mainstream theories or ideas that have not been published in professional peer-reviewed journals or are not part of current professional mainstream scientific discussion.
In climate, there are many open questions, relating to sensitivity, cloud effects, paleoclimate, approximations in modeling, the carbon cycle, and on, and on. We aren't going to resolve them, but understanding the credible alternatives is well worthwhile.

There are also a lot of questions which are not actually intellectually sound open questions at all, but simply misunderstandings or even outright crackpottery. There's a lot that is said outside the professional mainstream which has been enthusiastically passed around in the public domain as being of equal standing to genuine science. In some respects, a lot of this public debate (not all of it!) bears a significant similarity to the whole "intelligent design" movement."

Yes! And it would be quite useful for a lay person to be able to distinguish between legitimate questions and crack-pottery. There is so much noise on this issue that's its hard to get to what's substantive. It is so frustrating when you have people convinced with no evidential basis that global warming is a hoax, then you have "scientists" who post things like "global warming is a 100% certainty" (this was a statement I saw posted on the NYT by a suppossed climatologist which made me raise my eyebrow).

A general overview of what is relatively certain, what's generally agreed upon, what's questionable, and what's controversial would be great. Perhaps I should start a new thread for this?

Andre

Sep22-09, 04:57 PM

well as far as I'm concerned, there may be relative agreement about a BASIC climate sensitivity of about one degree celsius / Kelvin warming for doubling CO2.

So if you want to increase that to IPCC main figures of something like 2-4 degrees per doubling, you need predominance of positive feedback factors. That is questionable to controversial, like it or not.

Two approaches for that. On one hand statistics, investigating actual dynamic random walk temperature variation to be non-persistent, which suggest dominance of negative feedback, (several publications here (http://www.aai.ee/~olavi/)). On the other hand direct measurements as suggested here (http://www.leif.org/EOS/2009GL039628-pip.pdf).

Skyhunter

Sep22-09, 05:19 PM

then you have "scientists" who post things like "global warming is a 100% certainty"

Global warming is a fact. The instrumental record proves it to the very limits of scientific certainty.

Why should a scientist lend credibility to the global warming is a hoax crowd by giving a confusing nuanced answer about open questions and probability distribution curves?

sylas

Sep22-09, 07:14 PM

A general overview of what is relatively certain, what's generally agreed upon, what's questionable, and what's controversial would be great. Perhaps I should start a new thread for this?

Yes, I think you should; but your topic is going to be too general.

We have different ideas about what the problem really is.

What is "generally" agreed upon is not the same as "universally" agreed upon. For someone on the fence, who is confused, and who doesn't want to have to learn a whole pile of background physics, it is a perfectly sensible question to ask about the "consensus", in the sense of what is the view of the majority of scientists working on the subject. And by majority I mean almost overwhelming majority.

If you want to know a wider consensus going beyond the working scientists, then the consensus is weaker, and in the general public it is gone.

Terms like 100% certainty are not useful, and only rarely used by the working scientists. AGW is not a single proposition, but a whole body of propositions, some of which are more certain than others.

That the planet is warming, significantly, on decadal scales, is a measurement about as certain as you can get. It's ongoing work to measure that more accurately, and also to find how the warming is distributed, and to separate the warming trend from stationary variations.
That human factors have a major contribution is about as certain as you can get. But it is also certain that they are not the only factor, and there's a lot of ongoing work to identify and measure the various factors involved.
In particular, that CO2 is rising rapidly and that this is by far mostly from human industrial emissions is a fact about as certain as you can get. That this necessarily has a significant impact on Earth's energy balance is basic physics, about as certain as you can get.
A big open question is the one identified by Andre. What is the sensitivity of climate... how much does temperature change in response to energy balance forcing? The best we have is a range of possible values, which as Andre notes is about 2-4 degrees per doubling. It is more usually quoted as 2-4.5, or 1.5-4.5, which is the IPCC range in the 4th AR. That's not a 100% certainty range; more like a 90% certainty range. There continues to be work published from time to time which proposes smaller values, and that is legitimately part of the whole scientific project. If you just want the majority view, then 2-4.5 works. If you want to really get into the debate, then you'll have to look at other proposals also, on their own merits. But there are very few.

That's a brief road map of some of the questions associated with AGW, as I see it. The two biggest open questions are the magnitudes of other forcings and sensitivity to forcings.

Other forcings include in particular cloud and aerosol effects -- and identifying causes for them as well. There are significant anthropogenic factors in these other forcings as well, and most of these are much harder to sort out than CO2, which is comparatively straightforward by comparison.

The sensitivity of climate is being better constrained as time goes by, but there is still a substantial range of likely values, and a handful of published arguments for radically different values.

The guidelines at physicsforums do not limit us to the majority or consensus view. We are free to consider any work published in the peer reviewed literature. That includes a very wide range of perspectives; and being able to examine those on their own merits is great. This thread speaks of playing "devil's advocate". That means actually knowing and understanding the arguments you don't agree with yourself; both for those who tend to accept the reality of strong anthropogenic effects on climate, and those who are skeptical of strong human effects.

Some of these arguments are very technical. Quite apart from anything else, getting to follow them is going to involve learning more about the background physics, and that's what PF is about.

Cheers -- sylas

postscript.
On the other hand direct measurements as suggested here (http://www.leif.org/EOS/2009GL039628-pip.pdf).

There's no such thing as a direct measurement of sensitivity; and the paper you cite makes this clear as well. This is one of the legitimate handful of low estimates. It uses ERBE data. There's a fair bit of work been done with the ERBE data and sensitivity, and if you want majority views, then most of the ERBE based estimates are significantly higher than Andre's citation. To actually follow the details of how the estimates are made, either the low estimates in the paper by Linden and Choi, or the more conventional estimates from ERBE made by Wang, or Gregory and Foster, and others, you have to actually pull apart the details on their own merits. Just declaring one paper to solve the whole thing, or be a "direct" measurement, is foolish.

Xnn

Sep22-09, 08:40 PM

Within climate science, nothing is 100% certain. However, with respect to CO2 influence on the climate, the following can be said:

Equilibrium climate sensitivity is likely to be in the range of 2C to 4.5C with a most likely value of about 3C, based upon multiple observational and modelling constraints. It is very unlikely to be less than 1.5C.

page 88: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-ts.pdf

Notice:
Likely = 66% probability
Very Unlikely < 10% probability

In other words, it is more than very likely (>>90% probability) that climate sensitivity is > 1C, while the most likely value is about 3C.

So, while some may wish to argue that climate sensitivity is less than 1C, the odds are greatly against them being correct. However, to suggest that climate sensitivity may be less than 2C while an extreme statement is not out of the realm of possibility since the chance of it being correct is about 33%.

Probably the best thing to say is that there is a small, but not negligible, probability that climate sensitivity is less than 1C.

vanesch

Sep23-09, 02:58 AM

Yes! And it would be quite useful for a lay person to be able to distinguish between legitimate questions and crack-pottery. There is so much noise on this issue that's its hard to get to what's substantive. It is so frustrating when you have people convinced with no evidential basis that global warming is a hoax, then you have "scientists" who post things like "global warming is a 100% certainty" (this was a statement I saw posted on the NYT by a suppossed climatologist which made me raise my eyebrow).

You've got it. That's what makes this forum so hard to moderate. It is what I personally (I'm not talking on behalf of PF here) disliked most in some IPCC discourse and publications at a certain point: a certain lack of the typical self-criticism one usually finds in well-established science. When a supposed scientific discourse starts to sound like a commercial, or the program of a political party, I'm a bit lost.

BUT, but, how to express some reserves towards that, without opening the flood gates of crackpottery and low-level denial of basic established scientific fact ? That's the hard problem to solve here. And, as sylas pointed out, how can you solve it when certain experts have publicly shown not to show some "scientific self-criticism" ? Even a genuine renowed climate scientist wouldn't be recognized as an "objective expert" by "the other camp".

vanesch

Sep23-09, 03:01 AM

Notice:
Likely = 66% probability
Very Unlikely < 10% probability

In other words, it is more than very likely (>>90% probability) that climate sensitivity is > 1C, while the most likely value is about 3C.

I really wonder how one gets to these "probability" numbers. I know that they are Bayesian estimators, but as we know, Bayesian estimators need a priori probabilities of our "belief", and only work under the hypothesis that our error probability model is assumed correct.

This looks to me like trying to say that "Newtonian mechanics has 95% chance to be correct", no ?

sylas

Sep23-09, 03:38 AM

I really wonder how one gets to these "probability" numbers. I know that they are Bayesian estimators, but as we know, Bayesian estimators need a priori probabilities of our "belief", and only work under the hypothesis that our error probability model is assumed correct.

This looks to me like trying to say that "Newtonian mechanics has 95% chance to be correct", no ?

That is an excellent question. Such "probabilities" or "likelihoods" are inevitably subjective. Technically, they are obtained using a Bayesian analysis with assumed prior distributions, as you say... and it is the choice of prior distributions where you can't avoid being subjective.

There is a thread about this very point I started just recently. See A low likelihood for high climate sensitivity. This is about a new paper just out by Annan and Hargreaves, who argue that it is reasonable to reject with high confidence the likelihood of sensitivity values above 4.5; higher confidence than suggested in the 4th AR. The whole basis for the paper is not any new data; but a more "reasonable" choice of priors in the analysis.

Annan and Hargreaves do not propose any new "objective" likelihood measure, but face up to the inevitable subjective aspects of quantified likelihood estimates for a certain unknown real world number.

We've mentioned the range 1.5-4.5 which is widely used, on the basis of the IPCC 4th AR. This is obtained using a "uniform" prior, in which unreasonably high sensitivities are given the same prior expectation as any others, in a certain range (0 to 10, for example). A uniform prior is sometimes taken as a way of avoiding results that incorporate information other than the data being applied; Annan and Hargreaves argue that this is dubious. From their abstract:
In this paper, we investigate some of the assumptions underlying these estimates. We show that the popular choice of a uniform prior has unacceptable properties and cannot be reasonably considered to generate meaningful and usable results. When instead reasonable assumptions are made, much greater confidence in a moderate value for S is easily justified, with an upper 95% probability limit for S easily shown to lie close to 4oC, and certainly well below 6oC.

It seems to me that this is a well grounded criticism, and that exceptionally high sensitivities are less likely than you would think from the 4th assessment report.

Note that the choice of priors has more effect on the upper bound than the lower bound; this is a consequence of the "long tail" of sensitivities, explained in the thread.

Felicitations -- sylas

vanesch

Sep23-09, 05:07 AM

That is an excellent question. Such "probabilities" or "likelihoods" are inevitably subjective. Technically, they are obtained using a Bayesian analysis with assumed prior distributions, as you say... and it is the choice of prior distributions where you can't avoid being subjective.

This is one of the criticisms I naively have, but apparently it can be dealt with.

However, there's a second, more fundamental criticism, and that is the assumed inherent correcctness of the error probability model.

Imagine I have an unknown system of which I have to make a prediction of response for a given input signal. Now, we can take our system as a black box, a grey box, or a white box, which means that for the black box, we only take former input-output relationships and try to fit a "general-purpose" behavioural black box model on it (for instance, a dynamical neural network), or for the white box, we can study the physics of what's in the box, and write down the supposed dynamics of the model, with or without free parameters, or we can be somewhat in between (grey box) where some physical modeling is done, and where some behavioural modeling is done based upon experimental data.

Now, in order to do any Bayesian estimation, I do not only need a correct model of my system, I also need a correct probability estimation of the errors on my model. If I have a biased model, and/or erroneous error estimations of this model, my Bayesian estimator will be totally off, concerning its probability distribution. Its expectation value might be still more or less right, but its probability distribution will be totally off.

In fact, it is much more difficult to have a correct probability distribution for a Bayesian estimator than to have a more or less good estimator expectation value.

This is why I always expressed my reserves towards these probabilities.
Now, maybe this is due to my naivety, but I've been working in system identification, and usually people are much more prudent when they do such things, than what I've seen from the IPCC.

Of course, there is a totally subjective way in which these numbers DO make sense: you can take them as "this is what we think, *to our best knowledge*. In other words, if I *had to bet my money* on the sensitivity, I would use this Bayesian probability distribution because it is "the best I can do with what I know".

But estimating "the probability that such event will happen to be 10% to the best of my knowledge", and claiming that the probability of that event IS 10%, is different. The first statement is: "ok, this is what I know, but I can be wrong". The second is "what's true".

sylas

Sep23-09, 06:24 AM

But estimating "the probability that such event will happen to be 10% to the best of my knowledge", and claiming that the probability of that event IS 10%, is different. The first statement is: "ok, this is what I know, but I can be wrong". The second is "what's true".

These are not probabilities, but indications of confidence. The report is not saying that there is a known probability of an event. It is quantifying their level of confidence in a proposition.

In other words, the IPCC report, as I read it, more than any other scientific report I have ever seen, attempts to be careful about saying "this is what we think", with explicit acknowledgment of limited confidence. That's just my impression.

It doesn't matter all that much. I tend to use the IPCC assessment report as a secondary reference anyway. I nearly always go back to the primary literature to get at the details. The IPCC report is useful to summarize the state of play from many diverse working scientists; but it's not gospel. It's a useful resource. For reference, then, if anyone would like to check against the report itself:

The Physical Science Basis (http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg1_rep ort_the_physical_science_basis.htm) is the section of the fourth IPCC assessment report that is relevant to physicsforums and the underlying science of climate. It is the report of "working group 1". From the link, you can download the whole report (996 pages) as separate chapters; also the Technical Summary (http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-ts.pdf) and other materials.

In such a large report, it has been important to have a high level of consistency in how the report expresses its limited confidence in different propositions. A set of guidelines has been worked out for use throughout the report for expressing the level of confidence. These are described in box TS.1 (Technical summary, page 22-23), with additional pointers to other parts of the report that go into details of error and uncertainty handling.

In particular, the estimates of sensitivity are given on page 66 of the technical summary; with a brief overview on page 88 (quoted above by Xnn) and with more detail in the main report. See especially box 10.2, on page 798 (chapter 10). I quote here the tail end of that box:
Since the TAR, the levels of scientific understanding and confidence in quantitative estimates of equilibrium climate sensitivity have increased substantially. Basing our assessment on a combination of several independent lines of evidence, as summarised in Box 10.2 Figures 1 and 2, including observed climate change and the strength of known feedbacks simulated in GCMs, we conclude that the global mean equilibrium warming for doubling CO2, or ‘equilibrium climate sensitivity’, is likely to lie in the range 2°C to 4.5°C, with a most likely value of about 3°C. Equilibrium climate sensitivity is very likely larger than 1.5°C.

For fundamental physical reasons as well as data limitations, values substantially higher than 4.5°C still cannot be excluded, but agreement with observations and proxy data is generally worse for those high values than for values in the 2°C to 4.5°C range.

You could hardly be more thorough in avoiding a claim of "what's true"! They are explicit on the foundations of the estimate, and about the limits of their confidence. The values given of 2 to 4.5 are not probabilities of an event, but an indication of how confident they are about this range. The level here is "likely". For the "very likely" range, they give a lower bound only, of 1.5. The omission of an upper bound is deliberate, and reflects how hard it is to give a strong upper bound, given the nature of sensitivity and the "long tail".

In brief, they don't know the sensitivity. No-one does. The best they can do, as an assessment of the current state of knowledge, is that is it "very likely" more than 1.5, and "likely" to be in the range 2 to 4.5. You should read those as indications of how confident they are; not that this is a probability for an event.

In fact, the major criticism of the IPCC report, in this instance, is that it is too cautious in drawing conclusions. The paper by Annan and Hargreaves that I discussed is suggesting explicitly that the IPCC report could reasonably put an upper bound of 4.5, or even lower, in the "very likely" confidence level. It looks to me that they make a good case for this.

It doesn't bother me at all that people have different reactions to the IPCC assessment. One possible approach for moderating consistent with the guidelines would be to let the assessment be a guide to the range of views that are "mainstream", and rule out any argument that goes outside those bounds. I don't think that would be a good idea; but if you ever did decide to delimit boundaries for "mainstream" this would be your best option. But I think you have a much better approach already in place; which allows us to consider any view, from any individual, as long as they have taken that first step of getting it published in the peer reviewed literature.

So I don't mind at all that people differ in their reaction to the report. That's neither here nor there, and shouldn't be used to limit what propositions may be considered in the forum.

My own main interest is to help people understand better the physics of climate, and to learn more about it myself. It seems to me that a lot of debate on climate is based on visceral reactions rather than real physical comprehension of the various concepts.

Cheers -- sylas

---

PS. On reflection... I suggest that there is a problem in some quarters about how the IPCC report is used -- or indeed any scientific paper. Some people seem to treat the IPCC report as gospel, and that's dreadful. Same goes for treating any scientific paper as a final definition of what is known. Presenting a single paper as a final proof or disproof of a tricky scientific question is a misunderstanding of the nature of science. I don't personally think this is a fault of the IPCC report itself; which is more than usually careful about explicit recognition of limited confidence. It is rather a failure of understanding of a few people supposedly defending the report.

You may be able to identify in retrospect a major paper that has solved some problem; but that is generally something that is properly recognized some time after the publication, as other working scientists test and review its results. This is also why I would be against using the IPCC report as a limitation to define the mainstream for the purposes of moderation.

Xnn

Sep23-09, 11:37 AM

Xnn

Sep23-09, 11:41 AM

Concerning criticism of the the IPCC; has anybody noticed that peppered throughout their report are the identification of areas that have a low level of understanding?

Ice Sheet dynamics come to mind. A fair number of people are concerned about just how fast they may melt, but the IPCC hasn't made a definiative statement regarding them and for good reason.

sylas

Sep23-09, 05:31 PM

Consider the 3C/CO2 doubling most likely value.

CO2 levels are going up about 0.5% per year.
That works out to 0.015C/year of warming.

Now; look at the amount of observed global warming over the last 30 years.

It's about 0.016C/year.

In other words, observations are tending to support the most likely value.

That's technically incorrect on many levels.

First, the doubling value of 3 C/2xCO2 is an equilibrium response; not the transient response.

There's a lot more changing than just CO2. Taken in isolation, CO2 is the largest forcing, but there are a number of other forcings, both positive and negative, and they make a difference.

An increase of 0.5% per year is log2(1.005) of a doubling, and this is 0.0072. At 3 degrees per doubling you would have 3*0.0072 = 0.021 C/year.

As it turns out, observations are consistent with the estimates of sensitivity, but the argument is a bit different. It is not sufficient to give a strong constraint on the sensitivity estimate. If you look at the section of the technical summary you quoted previously, the next paragraph deals with "transient response" as opposed to "equilibrium sensitivity". Chapter 10 deals with the difference between these concepts in more detail. Here's the extract (page 88, technical summary)
The transient climate response is better constrained than the equilibrium climate sensitivity. It is very likely larger than 1°C and very unlikely greater than 3°C. {10.5}

With a transient response 2°C per doubling, and with an increase of 0.5% per year CO2, and in the absence of all other forcings, you should expect a temperature increase trend of about 2*log2(1.005) = 0.0144 C/year. Of course, there are other forcings as well; but all told this is why transient response is better constrained. The available data for the immediate present allows you to constrain it, where equilibrium response requires an additional level of indirection to get from observations to a number.

Also relevant is a recent thread with a discussion of the cummulative carbon emissions response (CCR), which tends to reflect transient climate response rather than equilibrium climate response. There were two recent papers on this, which are discussed in msg #83 and following of thread "Estimating the impact of CO2 on global mean temperature".

Cheers -- sylas

Xnn

Sep23-09, 07:54 PM

Thanks sylas;

So, doing this in natural logs, the calculation is 0.016/0.0072 = 2.2 C/CO2 doubling; using the last 30 years of global observational data if other forcings are ignored.

Not sure if how significant other forcings are.

sylas

Sep23-09, 09:40 PM

Not sure if how significant other forcings are.

Neither is anyone else; there are significant uncertainties in other forcings. CO2 is the simplest forcing to evaluate and is known to quite high accuracy. Other forcings are known, but with larger bounds of accuracy. The bounds are sufficient to conclude with strong confidence that greenhouse effects are the largest forcing, and that CO2 is the largest contributor to that. But the lack of certainty in other forcings still means a large spread of uncertainty about total forcing.

I've given a widely repeated diagram in msg #66 of thread "Estimating the impact of CO2 on global mean temperature", outlining estimates and uncertainties for forcings. It can be found also as figure 2.20, on page 203 (chapter 2) of the 4th AR (http://www.ipcc.ch/ipccreports/ar4-wg1.htm). The estimates are quantified, with 90% confidence bounds, in table 2.12, page 204.

Felicitations -- sylas

PS. As an added wrinkle... a forcing is a change from one time to another. The table I've shown is giving the forcings from 1750 to the present. But if you want to look at the last 30 years, then the picture changes again, generally making the greenhouse effects and CO2 in particular even more significant for the immediate rate of change. The immediate rate of change also is affected by changes in heat uptake in the ocean, which will impact rates of change in much the same way as a forcing.

Saul

Sep25-09, 08:13 AM

The other explanation for the 20th century warming is a decrease in planetary clouds rather than AWG, in particular CO2.

The observations do not show a steady increase in the base line planetary temperature about which planetary temperature oscillates. Planetary temperature has in fact cooled slightly post 1998.

http://www.woodfortrees.org/plot/hadcrut3vgl/from:1980/to:2009.8/normalise

http://wattsupwiththat.com/2009/09/04/uah-global-temperature-down-in-august-181%C2%B0c-sh-sees-biggest-drop-of-0-4%C2%B0c/

As I noted further up in the this thread planetary temperature in the 20th century has strongly correlated with geomagnetic field change measured by the parameter Ak that is in turn modulated by solar wind bursts. The solar wind burst remove cloud forming ions by a process called electroscavenging. The sudden warming events in planetary temperature records and the longer term warming and cooling trends correlate with Ak.

http://www.atmos-chem-phys.org/5/1721/2005/acp-5-1721-2005.html

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984–2000

All cloud types show a linearly decreasing trend over the study period, with the low-level clouds having the largest trend, equal to −3.9±0.3% in absolute values or −9.9±0.8% per decade in relative terms. Of course, there are still some uncertainties, since the changes in low-level clouds derived from the ISCCP-D2 data, are not necessarily consistent with changes derived from the second Stratospheric Aerosols and Gas Experiment (SAGE II, Wang et al., 2002) and synoptic observations (Norris, 1999). Nevertheless, note that SAGE II tropical clouds refer to uppermost opaque clouds (with vertical optical depth greater than 0.025 at 1.02μm), while the aforementioned synoptic cloud observations are taken over oceans only. The midlevel clouds decreased by 1.4±0.2% in absolute values or by 6.6±0.8% per decade in relative terms, while the high-level ones also decreased by 1.2±0.4% or 3±0.9% per decade in relative terms, i.e. less than low and middle clouds. Thus, the VIS/IR mean tropical (30_ S–30_ N) low-level clouds are found to have undergone the greatest decrease during the period 1984–2000, in agreement with the findings of Chen et al. (2002) and Lin et al. (2004).

http://news.yahoo.com/s/mcclatchy/20090819/sc_mcclatchy/3295216

WASHINGTON — Has Earth's fever broken?
Official government measurements show that the world's temperature has cooled a bit since reaching its most recent peak in 1998.

"It's entirely possible to have a period as long as a decade or two of cooling superimposed on the long-term warming trend," said David Easterling , chief of scientific services at NOAA's National Climatic Data Center in Asheville, N.C.

So far this year, the high has been 0.42 degrees Celsius (0.76 degrees Fahrenheit), above the 20-year average, clearly cooler than before.

vanesch

Sep25-09, 08:31 AM

As I noted further up in the this thread planetary temperature in the 20th century has strongly correlated with geomagnetic field change measured by the parameter Ak that is in turn modulated by solar wind bursts. The solar wind burst remove cloud forming ions by a process called electroscavenging. The sudden warming events in planetary temperature records and the longer term warming and cooling trends correlate with Ak.

The problem is that the planetary temperature in the 20th century also correlates with the logarithm of the average number of transistors on an Intel processor chip...

Saul

Sep25-09, 08:40 AM

The problem is that the planetary temperature in the 20th century also correlates with the logarithm of the average number of transistors on an Intel processor chip...

Do you have a paper to show the correlation?

Please explain the cooling post 1998.

I provided papers that shows the correlation, papers that provide a cause to explain the observations, and papers to explain the mechanism.

What is your point? Or problem?

Saul

Sep25-09, 08:55 AM

Galteeth's comment was:

This is a fascinating forum, and these climate discussions are very interesting and educational. I couldn't help but notice however that it seems posters tend to line up along sides on the issue of AGW (or perhaps the degree to which they are skeptical of the consensus). I think it would be interesting to see people play devil's advocate and argue for the other position, or rather acknowledge data that does not support their view (on both sides).

There are most definitely basic observations that do not support the AWG hypothesis. There have been a series of papers that have been written concerning the discrepancy between prediction and observations.

The science is interesting. A pointless sarcastic monologue is not.

Because there currently appears to be a deep solar magnetic cycle minimum, there should be observational evidence and papers to clarify the problem situation. We can have some fun reading and discussing those papers and discussing the observational evidence.

The competing scientific explanation for the 20th century warming is solar modulation of planetary cloud cover. As noted in the past cosmogenic isotopes changes correlate with abrupt planetary temperature change. There is smoking gun evidence at each of the cyclic abrupt climate change events.

vanesch

Sep25-09, 09:20 AM

What is your point? Or problem?

The point is that finding a correlation doesn't indicate a causal relationship, and even if so, it doesn't even indicate which way. Now, there can (I didn't check) be a correlation with solar activity, why not. The mechanism you mention can be active.

However, you are not going to convince me that the mechanism of cloud formation through solar activity is simpler physics, which is less prone to modelling errors, and to which there are less complex feedback factors working, than the heat transport problem of an atmosphere containing some gases that interact with IR radiation, which is based upon rather elementary thermodynamics, and of which several basic aspects are easily checked and known for tens of years (like the lapse rate, or the black body properties of gases).

In other words, the warming of the last century can be for sure find its origins in many elements, but the CO2 is definitely a part in it, and it is probably the easiest part to calculate, because at least the forcing due to it is easy to estimate.

The point is that even if you had a straight-forward model that no-body can doubt because based upon very elementary physics for your solar activity stuff that gives you the expected change in cloud cover as function of the solar activity, calculated from first principles only, and not using any climate data, still you would be faced with exactly the same problem as the one with CO2: the climate sensitivity. Even if you had the perfect model that gives you without an ounce of doubt, from first principles, the cloud cover as a function of solar activity, the only thing you would be able to get from that, is a forcing (so many watts per square meter). The question of how temperature is dependent on that is exactly the same as for the CO2 forcing: the sensitivity.

Now, at least the forcing is easy to calculate with CO2, because for that there DOES exist a simple and straightforward physics model based upon first principles.

So it might very well be that your mechanism ALSO exists, and is ALSO a significant drive - I don't know. But to say that it is a *more straightforward* explanation than CO2 seems to me to push things, no ?

Skyhunter

Sep25-09, 09:35 AM

Do you have a paper to show the correlation?

Please explain the cooling post 1998.

I provided papers that shows the correlation, papers that provide a cause to explain the observations, and papers to explain the mechanism.

What is your point? Or problem?

Denier blogs are not scientific papers. Therefore you have failed to meet the standards of this forum.

There is no cooling trend since 1998. 1998 was an anomalous year, influenced by a very strong el nino event. The long term trend did plateau slightly, but has remained positive.

http://www.ncdc.noaa.gov/img/climate/research/global-jan-dec-error-bar-pg.gif

Saul

Sep25-09, 09:42 AM

The point is that finding a correlation doesn't indicate a causal relationship, and even if so, it doesn't even indicate which way. Now, there can (I didn't check) be a correlation with solar activity, why not. The mechanism you mention can be active.

However, you are not going to convince me that the mechanism of cloud formation through solar activity is simpler physics, which is less prone to modelling errors, and to which there are less complex feedback factors working, than the heat transport problem of an atmosphere containing some gases that interact with IR radiation, which is based upon rather elementary thermodynamics, and of which several basic aspects are easily checked and known for tens of years (like the lapse rate, or the black body properties of gases).

In other words, the warming of the last century can be for sure find its origins in many elements, but the CO2 is definitely a part in it, and it is probably the easiest part to calculate, because at least the forcing due to it is easy to estimate.

The point is that even if you had a straight-forward model that no-body can doubt because based upon very elementary physics for your solar activity stuff that gives you the expected change in cloud cover as function of the solar activity, calculated from first principles only, and not using any climate data, still you would be faced with exactly the same problem as the one with CO2: the climate sensitivity. Even if you had the perfect model that gives you without an ounce of doubt, from first principles, the cloud cover as a function of solar activity, the only thing you would be able to get from that, is a forcing (so many watts per square meter). The question of how temperature is dependent on that is exactly the same as for the CO2 forcing: the sensitivity.

Now, at least the forcing is easy to calculate with CO2, because for that there DOES exist a simple and straightforward physics model based upon first principles.

So it might very well be that your mechanism ALSO exists, and is ALSO a significant drive - I don't know. But to say that it is a *more straightforward* explanation than CO2 seems to me to push things, no ?

vanesch,

I am not trying to convince you of anything. I am trying explain these observations.

Those advocating the AWG position (AWG caused 90% of the 20th century warming. Deny the cooling occurred or attribute cooling to satellite problems.) in this forum have not acknowledge the most basic fact which is that the 20th planetary temperature changes did not correlate with the CO2 changes. Changes in planetary cloud cover do correlate with the 20th century temperature rise.

A scientific mind ask why, is interesting in a scientific explanation. You and the other AWG supports in the forum do not acknowledge that there is a problem situation. Something that requires explanation.

The point is you write in capital letters. I do not understand the emotion. Science is science. The truth is the truth. What will happen will happen.

The are multiple observations (for example the current cooling trend and the increase in sea ice in the arctic and antarctic) and papers that do not support the AWG hypothesis.

http://www.woodfortrees.org/plot/hadcrut3vgl/from:1980/to:2009.8/normalise

http://wattsupwiththat.com/2009/09/04/uah-global-temperature-down-in-august-181%C2%B0c-sh-sees-biggest-drop-of-0-4%C2%B0c/

http://www.atmos-chem-phys.org/5/1721/2005/acp-5-1721-2005.html

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984–2000

All cloud types show a linearly decreasing trend over the study period, with the low-level clouds having the largest trend, equal to −3.9±0.3% in absolute values or −9.9±0.8% per decade in relative terms. Of course, there are still some uncertainties, since the changes in low-level clouds derived from the ISCCP-D2 data, are not necessarily consistent with changes derived from the second Stratospheric Aerosols and Gas Experiment (SAGE II, Wang et al., 2002) and synoptic observations (Norris, 1999). Nevertheless, note that SAGE II tropical clouds refer to uppermost opaque clouds (with vertical optical depth greater than 0.025 at 1.02μm), while the aforementioned synoptic cloud observations are taken over oceans only. The midlevel clouds decreased by 1.4±0.2% in absolute values or by 6.6±0.8% per decade in relative terms, while the high-level ones also decreased by 1.2±0.4% or 3±0.9% per decade in relative terms, i.e. less than low and middle clouds. Thus, the VIS/IR mean tropical (30_ S–30_ N) low-level clouds are found to have undergone the greatest decrease during the period 1984–2000, in agreement with the findings of Chen et al. (2002) and Lin et al. (2004).

Saul

Sep25-09, 09:51 AM

Denier blogs are not scientific papers. Therefore you have failed to meet the standards of this forum.

There is no cooling trend since 1998. 1998 was an anomalous year, influenced by a very strong el nino event. The long term trend did plateau slightly, but has remained positive.

Skyhunter,
Science is the discussion of observations. Planetary temperature is dropping. Antarctic and Arctic Sea ice is increasing.

Name calling "denier blogs" is a sign that you are not interesting in the problem situation from a scientific standpoint. Why the emotion? The observations do not support the AWG hypothesis.

http://news.yahoo.com/s/mcclatchy/20090819/sc_mcclatchy/3295216

http://www.woodfortrees.org/plot/hadcrut3vgl/from:1980/to:2009.8/normalise

WASHINGTON — Has Earth's fever broken?
Official government measurements show that the world's temperature has cooled a bit since reaching its most recent peak in 1998.

vanesch

Sep25-09, 10:03 AM

Those advocating the AWG position (AWG caused 90% of the 20th century warming. Deny the cooling occurred or attribute cooling to satellite problems.)

This is not what I would call the defining position of AGW. AGW means, at least, that's how I understand it, that human emissions of greenhouse gasses are significant enough to cause an observable extra warming on top of all the other forcings that there might be, in the coming centuries. Then the scientific debate goes about how much exactly.

And then the non-scientific AGW debate goes about what this is going to do to humanity and the biosphere, and whether that is a bad thing in the first place, and if so, what, if anything, we should/can do about it.

Saul

Sep25-09, 10:19 AM

This is not what I would call the defining position of AGW. AGW means, at least, that's how I understand it, that human emissions of greenhouse gasses are significant enough to cause an observable extra warming on top of all the other forcings that there might be, in the coming centuries. Then the scientific debate goes about how much exactly.

And then the non-scientific AGW debate goes about what this is going to do to humanity and the biosphere, and whether that is a bad thing in the first place, and if so, what, if anything, we should/can do about it.

The AWG position is that a doubling of from 280 ppm to 560 ppm will cause the planet to warm 3C to 5C.

The AWG position is not that an increase in CO2 from 280 ppm to 560 ppm will cause 0.75C increase in planetary temperature.

The scientific formula for CO2 forcing is logarithmic. The current increase (from 280 ppm to 380 ppm) will if the formula matches reality result in an increase in forcing of around 2.7 w/m^2 of the total calculated 3.7 w/m^2 that the formula predicts will result from a doubling from 280 ppm to 560 ppm.

Rather than discuss the recent planetary cooling, it is denied. There cannot be a long term cooling trend if there was an increase in forcing that never goes away of 2.7 w/m^2.

That is the problem situation from the AWG position. The CO2 must warm the planet every day if the mechanism exists as hypothesized.

What it appears based on the shape of planetary temperature change, is CO2 saturates or at least partially saturates from a perspective of the mechanism. The why and what will happen next due to the abrupt solar magnetic cycle change, is an interesting question.

The key question is the magnitude of up coming planetary temperature change.

Skyhunter

Sep25-09, 10:23 AM

Skyhunter,
Science is the discussion of observations. Planetary temperature is dropping. Antarctic and Arctic Sea ice is increasing.

Name calling "denier blogs" is a sign that you are not interesting in the problem situation from a scientific standpoint. Why the emotion? The observations do not support the AWG hypothesis.

http://news.yahoo.com/s/mcclatchy/20090819/sc_mcclatchy/3295216

http://www.woodfortrees.org/plot/hadcrut3vgl/from:1980/to:2009.8/normalise

Denier blogs or fellowship for scientific truth, it doesn't matter what you call them. They are not credible sources and therefore against forum rules.

Saul

Sep25-09, 10:41 AM

Denier blogs or fellowship for scientific truth, it doesn't matter what you call them. They are not credible sources and therefore against forum rules.

Skyhunter what is your point or problem? You appear not to want to discuss the science and instead try to stop anyone else from discussing the science, the problem situation.

The AWG position is that a doubling of CO2 from 280 ppm to 560 ppm will cause the planet to warm 3C to 5C. Based on the AWG formula the increase from 280 ppm to 380 ppm should have resulted in an increase in forcing of 2.7 w/m^2 of the total 3.7 w/m^2, 24 hours a day, seven days a week.

The AWG forcing mechanism cannot appear in January and then disappear in June.

There is no evidence in the planetary temperature changes of a steady increase in of 2.7 w/m^2.

The other explanation for the 20th century warming is a change in planetary clouds. The forcing mechanism that increases and decreases planetary clouds can change and hence can explain the observations.

http://www.atmos-chem-phys.org/5/172...1721-2005.html

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984–2000

All cloud types show a linearly decreasing trend over the study period, with the low-level clouds having the largest trend, equal to −3.9±0.3% in absolute values or −9.9±0.8% per decade in relative terms. Of course, there are still some uncertainties, since the changes in low-level clouds derived from the ISCCP-D2 data, are not necessarily consistent with changes derived from the second Stratospheric Aerosols and Gas Experiment (SAGE II, Wang et al., 2002) and synoptic observations (Norris, 1999). Nevertheless, note that SAGE II tropical clouds refer to uppermost opaque clouds (with vertical optical depth greater than 0.025 at 1.02μm), while the aforementioned synoptic cloud observations are taken over oceans only. The midlevel clouds decreased by 1.4±0.2% in absolute values or by 6.6±0.8% per decade in relative terms, while the high-level ones also decreased by 1.2±0.4% or 3±0.9% per decade in relative terms, i.e. less than low and middle clouds. Thus, the VIS/IR mean tropical (30_ S–30_ N) low-level clouds are found to have undergone the greatest decrease during the period 1984–2000, in agreement with the findings of Chen et al. (2002) and Lin et al. (2004).

http://news.yahoo.com/s/mcclatchy/20...latchy/3295216

WASHINGTON — Has Earth's fever broken?
Official government measurements show that the world's temperature has cooled a bit since reaching its most recent peak in 1998.

"It's entirely possible to have a period as long as a decade or two of cooling superimposed on the long-term warming trend," said David Easterling , chief of scientific services at NOAA's National Climatic Data Center in Asheville, N.C.

So far this year, the high has been 0.42 degrees Celsius (0.76 degrees Fahrenheit), above the 20-year average, clearly cooler than before.

Skyhunter

Sep25-09, 10:43 AM

The Earth is not cooling.

Short term trends are flat, not negative. As the current el nino event develops global temperatures are once again on the rise.

The CO2 must warm the planet every day if the mechanism exists as hypothesized.

This is a strawman argument.

There is nothing in the AGW theory that requires temperatures to rise everyday.

Skyhunter

Sep25-09, 10:45 AM

Saul,

If you want to discuss science, then provide a scientific source.

We are not allowed to discuss psuedo-science on this forum.

Saul

Sep25-09, 10:52 AM

The Earth is not cooling.

Short term trends are flat, not negative. As the current el nino event develops global temperatures are once again on the rise.

This is a strawman argument.

There is nothing in the AGW theory that requires temperatures to rise everyday.

Skyhunter,

The hypothesized 2.7 w/m^2 heating due to CO2 increasing from 280 ppm to 380 ppm does not go away. It is there 24 hours a day, seven days a week.

Fundamental science shows the CO2 greenhouse affect is logarithmic. Each additional CO2 molecule has less affect than the molecule that was added before. The majority of the climate forcing has already occurred based on the basic science.

Remember the AWG position is not only that additional CO2 will cause the planet to slightly warm (say 0.75C), but rather that the planet will warm 3C to 5C, due to a doubling of CO2 from 280 ppm to 560 ppm.

Significant planetary cooling this winter for example would be very difficult to explain if the AWG hypothesized mechanism is correct.

Saul

Sep25-09, 10:58 AM

Saul,

If you want to discuss science, then provide a scientific source.

We are not allowed to discuss psuedo-science on this forum.

Skyhunter,
Your comment is irrational. Not logical. It does not match my comment. It makes sense if your objective is to try to stop me from commenting.

It has no connection with my comment scientifically. I am only interested in the science. I am not trying to change your personal point of view.

The other explanation for the 20th century warming is a change in planetary clouds. The forcing mechanism that increases and decreases planetary clouds can change and hence can explain the observations.

http://www.atmos-chem-phys.org/5/172...1721-2005.html

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984–2000

All cloud types show a linearly decreasing trend over the study period, with the low-level clouds having the largest trend, equal to −3.9±0.3% in absolute values or −9.9±0.8% per decade in relative terms. Of course, there are still some uncertainties, since the changes in low-level clouds derived from the ISCCP-D2 data, are not necessarily consistent with changes derived from the second Stratospheric Aerosols and Gas Experiment (SAGE II, Wang et al., 2002) and synoptic observations (Norris, 1999). Nevertheless, note that SAGE II tropical clouds refer to uppermost opaque clouds (with vertical optical depth greater than 0.025 at 1.02μm), while the aforementioned synoptic cloud observations are taken over oceans only. The midlevel clouds decreased by 1.4±0.2% in absolute values or by 6.6±0.8% per decade in relative terms, while the high-level ones also decreased by 1.2±0.4% or 3±0.9% per decade in relative terms, i.e. less than low and middle clouds. Thus, the VIS/IR mean tropical (30_ S–30_ N) low-level clouds are found to have undergone the greatest decrease during the period 1984–2000, in agreement with the findings of Chen et al. (2002) and Lin et al. (2004).

http://news.yahoo.com/s/mcclatchy/20...latchy/3295216

WASHINGTON — Has Earth's fever broken?
Official government measurements show that the world's temperature has cooled a bit since reaching its most recent peak in 1998.

"It's entirely possible to have a period as long as a decade or two of cooling superimposed on the long-term warming trend," said David Easterling , chief of scientific services at NOAA's National Climatic Data Center in Asheville, N.C.

So far this year, the high has been 0.42 degrees Celsius (0.76 degrees Fahrenheit), above the 20-year average

Skyhunter

Sep25-09, 11:05 AM

Saul,

You said:

That is the problem situation from the AWG position. The CO2 must warm the planet every day if the mechanism exists as hypothesized.

and

The AWG forcing mechanism cannot appear in January and then disappear in June.

and

Significant planetary cooling this winter for example would be very difficult to explain if the AWG hypothesized mechanism is correct.

These are strawmen arguments, red herrings. The AGW forcing does not alter the fact that climate has other shorter and longer term oscillations that account for daily, seasonal, annual, decadal, and millennial climate or temperature changes.

vanesch

Sep25-09, 11:08 AM

The AWG position is that a doubling of from 280 ppm to 560 ppm will cause the planet to warm 3C to 5C.

?

I think you are fighting a straw man.
First of all, even the IPCC is not giving these limits (and I have - as I said earlier - my own doubts on the rigor by which these are "hard limits" or rather "to the best of our knowledge today" kind of indications). As far as I remember, they give something like 1.5 - 4.5 C with a 90% confidence limit or something. If human CO2 exhaust would double the atmospheric content and would warm only 1.5 degrees, that would also be AGW. Even 0.5 degrees in my book would be AGW, although the guys from the IPCC consider that, given their current understanding, rather improbable. However, 0.01 degree wouldn't. Because that's not noticeable or measurable.

Second, warming with respect to what ? Warming with respect to what there would have been without CO2 exhaust. The base line doesn't need to be constant. So even a cooling can be under AGW influence, if it cools less than it would have cooled without CO2 exhaust. But that's not directly measureable.

The AWG position is not that an increase in CO2 from 280 ppm to 560 ppm will cause 0.75C increase in planetary temperature.

I would think that it is still AGW, although several people tend to think it will be stronger.

The scientific formula for CO2 forcing is logarithmic. The current increase (from 280 ppm to 380 ppm) will if the formula matches reality result in an increase in forcing of around 2.7 w/m^2 of the total calculated 3.7 w/m^2 that the formula predicts will result from a doubling from 280 ppm to 560 ppm.

Yes. So ? There can be long delays before the final value is reached. These delays can be of the matter of decades or centuries.

Rather than discuss the recent planetary cooling, it is denied. There cannot be a long term cooling trend if there was an increase in forcing that never goes away of 2.7 w/m^2.

Of course there could be if there were other forcings that were negative and larger. If tomorrow the sun "goes out" then it will for sure cool. But according to AGW, it will cool slightly less (fast) than it would without CO2. That's still AGW.

The anti-AGW position is rather that human CO2 exhaust doesn't have the slightest noticeable influence on the climate system.

But the other error is to think that you can do statistics over a decade or so. You need of the order of a century to be able to see small trends like these because the average values are only that: averages. And the statistical spread around them is very big. They are the "high frequency" components that are not understood, that are chaotic,...

That is the problem situation from the AWG position. The CO2 must warm the planet every day if the mechanism exists as hypothesized.

No, of course not. There must only a trend on the scale of centuries or many decades. And even then, a trend with respect to an unknown "base line" which is what there would have been without human exhaust, but which we can of course not measure.

Of course, the stronger the trend, and the less the baseline is supposed to change, the sooner the data will show up evidence.

The absolute temperature variation BY ITSELF doesn't say anything about AGW by itself.

Saul

Sep25-09, 11:28 AM

?

Vanesch & Skyhunter,

I think we have beaten this subject to death. Let's agree to disagree.

Let's summarize.

I have provided papers that show the 20th century planetary warming could be due to a reduction in planetary cloud cover. See above if anyone is interested.

There is currently an abrupt interruption of the solar magnetic cycle which has reduced the strength of the heliosphere and has caused GCR to increase by 18%. There has not been an increase in planetary clouds because there has been a three times increase in solar wind bursts during this current solar cycle minimum. I have provided papers to support these statements.

The solar wind bursts have started to abate.

Based on the planetary cloud mechanism, planetary cloud should now start to increase, due to a reduction in the solar wind bursts and due to the increased GCR.

So rather than argue whether the solar modulation of planetary cloud mechanism exists or does not exist, we can just watch planetary temperature and see if it does drop. I am interested because I do not understand the delays in the mechanisms and I am unsure of the magnitude of the change.

I will keep an eye out for any interesting planetary temperature observations. Have you been watching the current Arctic and Antarctic sea ice cover anomaly?

Skyhunter

Sep25-09, 11:44 AM

I have provided papers that show the 20th century planetary warming could be due to a reduction in planetary cloud cover. See above if anyone is interested.

Your sources are not scientific, therefore may not be discussed here.

There is currently an abrupt interruption of the solar magnetic cycle which has reduced the strength of the heliosphere and has caused GCR to increase by 18%. There has not been an increase in planetary clouds because there has been a three times increase in solar wind bursts during this current solar cycle minimum. I have provided papers to support these statements.

I have been following the current solar minimum, solar winds have been relatively calm for the past year.

Although they have been much higher than during the cycle 23 minimum.

Based on the planetary cloud mechanism, planetary cloud should now start to increase, due to a reduction in the solar wind bursts and due to the increased GCR.

Planetary cloud cover should have begun increasing 18 months ago according to the GCR hypothesis.

So rather than argue whether the solar modulation of planetary cloud mechanism exists or does not exist, we can just watch planetary temperature and see if it does drop. I am interested because I do not understand the delays in the mechanisms and I am unsure of the magnitude of the change.

I am uncertain that the mechanism even exists. And even if it does, since temperatures are still rising it has little effect on global temperatures.

I will keep an eye out for any interesting planetary temperature observations. Have you been watching the current Arctic and Antarctic sea ice cover anomaly?

I visit the NSIDC site 3-5 times a week.

Saul

Sep25-09, 12:06 PM

Your sources are not scientific, therefore may not be discussed here. I visit the NSIDC site 3-5 times a week.

http://www.agu.org/pubs/crossref/2009/2009JA014342.shtml
Skyhunter,

You must have missed this paper. Let's agree to disagree about the prediction of what is about to happen. Let's wait until there is new planetary temperature data to discuss. I will keep an eye out for new papers.

This should be an interesting scientific period if I understand the mechanisms.

If the Sun is so quiet, why is the Earth ringing? A comparison of two solar minimum intervals

Observations from the recent Whole Heliosphere Interval (WHI) solar minimum campaign are compared to last cycle's Whole Sun Month (WSM) to demonstrate that sunspot numbers, while providing a good measure of solar activity, do not provide sufficient information to gauge solar and heliospheric magnetic complexity and its effect at the Earth.

The present solar minimum is exceptionally quiet, with sunspot numbers at their lowest in 75 years and solar wind magnetic field strength lower than ever observed. Despite, or perhaps because of, a global weakness in the heliospheric magnetic field, large near-equatorial coronal holes lingered even as the sunspots disappeared. Consequently, for the months surrounding the WHI campaign, strong, long, and recurring high-speed streams in the solar wind intercepted the Earth in contrast to the weaker and more sporadic streams that occurred around the time of last cycle's WSM campaign.

In response, geospace and upper atmospheric parameters continued to ring with the periodicities of the solar wind in a manner that was absent last cycle minimum, and the flux of relativistic electrons in the Earth's outer radiation belt was elevated to levels more than three times higher in WHI than in WSM. Such behavior could not have been predicted using sunspot numbers alone, indicating the importance of considering variation within and between solar minima in analyzing and predicting space weather responses at the Earth during solar quiet intervals, as well as in interpreting the Sun's past behavior as preserved in geological and historical records.

Skyhunter

Sep25-09, 12:34 PM

You are speculating that

GCR drives cloud formation, as yet a still unproven hypothesis.
The solar wind modulates this as speculative process.

Since the global temperature trend is still positive, and we are entering a positive ENSO phase, then it is likely that global temperatures will continue to rise.

Darryl

Sep28-09, 11:10 AM

My take on this is, it's not a valid scientific experiment, there is no control subject and it it was "an experiment" that should be allowed to run it's course then what happens if the global warming does swing out of control.

talking about control, I see this as a feedback control loop issue, if you have 'tuned' a feedback control loop you generally have 2 knobs, gain and damping.

Too little damping and the process will go out of control, it will not just swing to one extreme it will begin to oscilate until it hardlines on one extreme.

Too little damping or too much gain will achieve the same result.

To me, cutting down CO2 absorbing trees is reducing the "damping" parameter, and releasing fossilised CO2 in increasing the gain in the system.

It's not an experiment, we dont have anywhere els to go if we are wrong, So possibly erring on the side of causion might be wise.

"Lets wait and see" is not good enough.

D H

Sep28-09, 11:30 AM

My take on this is, it's not a valid scientific experiment, there is no control subject and it it was "an experiment" that should be allowed to run it's course then what happens if the global warming does swing out of control.
What experiment are you talking about?

It appears you have a misperception of how the scientific method is employed in fields such as anthropology, astronomy/cosmology, and climatology/meteorology. We don't know how to build a time machine, and even if we did, going back in time and experimenting on Mitochondrial Eve would not be deemed as kosher. Anthropologists can only observe, and their observations are limited to ancient bones and shards of flint. Astronomers similarly cannot create in the lab galaxies that are billions of light years apart. They can observe them by telescope. Just because anthropologists and astronomers can't perform controlled experiments with all the trappings does not mean that anthropology and astronomy are not science.

The same goes for meteorology and climatology. Scientists can create scaled-down models of some phenomena, but scaling things down to lab size is always fraught with problems. (The scaling problem is why the aerodynamics industry likes to use full-scale wind tunnel as the ultimate test of what happens to a vehicle.) The best way to determine the weather and climate is to observe it. It is still science.