Playing Devil's advocate on climate

  • Thread starter Galteeth
  • Start date
  • Tags
    Climate
In summary: Second, the insistence that the "deniers" are somehow conspiring to deceive the public and suppress the truth about climate change. Third, the false dichotomy of "skeptics" and "believers".In summary, this forum is fascinating, and the 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 acknowledeld
  • #1
Galteeth
69
1
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).
 
Earth sciences news on Phys.org
  • #2
Yes, that's right. That's what we try to do for ages here, but several people tend to pick sides from the start. Not only on PF. It seems to be a trench war, instead of a scientific debate.
 
  • #3
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 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 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, 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?

sc_Rss_compare_TS_channel_tlt_v03_2.png


Source: http://www.ssmi.com/msu/msu_data_description.html#figures
 
Last edited by a moderator:
  • #4
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.

This is why there is no "default" position and a "challenger" position here. There are two theories, one that should theoretically demonstrate that CO2 cannot have any observable effect, and the other that should indicate what is the mechanism by which CO2 could give rise to some warming. I think that the first theory is making the strongest claims, actually.

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.

It is true that simple atmospheric physics indicates *a priori* a (modest) warming, all else equal. So defenders of the "no warming possible" theory should demonstrate that this basic effect has to be canceled out exactly by some more involved mechanism. Defenders of high warming values, should demonstrate the existence of strong positive feedbacks.

In any case, it is a scientific inquiry.
 
  • #5
vanesch said:
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. https://www.amazon.com/dp/0980076315/?tag=pfamazon01-20 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.
 
Last edited by a moderator:
  • #6
Andre said:
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 [thread=334005]A low likelihood for high climate sensitivity[/thread]. 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 [post=2195419]msg #47[/post] 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
 
Last edited:
  • #7
Andre said:
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.
 
  • #8
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".

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.
 
Last edited:
  • #9
sylas said:
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 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 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.
 
Last edited:
  • #10
Andre said:
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 [post=2318289]msg #171[/post] 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
 
Last edited:
  • #11
Andre said:
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.
 
  • #12
vanesch said:
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/wikiped...g/800px-Carbon14_with_activity_labels.svg.png

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/q...8/29&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.
 
Last edited:
  • #13
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
 
Last edited by a moderator:
  • #14
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 into restate your own perspective on a climate related topic, you've completely missed the whole point.
 
  • #15
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)


http://geology.about.com/od/extinction/a/aa_permotrias.htm"
 
Last edited by a moderator:
  • #16
sylas said:
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 into 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.

Vostok-ice-core-petit.png


http://en.wikipedia.org/wiki/File:Vostok-ice-core-petit.png
 
  • #17
Skyhunter said:
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, http://www.solcomhouse.com/siberiantraps.htm

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

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

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.
 
Last edited by a moderator:
  • #18
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.
 
  • #19
Galteeth said:
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.
 
  • #20
Galteeth said:
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.

Anyway, this thread used to be about the real numbers. However, it seems to be modified a bit.
 
  • #21
Andre said:
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.
 
  • #22
Andre said:
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.

Anyway, this thread 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.
 
  • #23
Galteeth said:
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.
 
  • #24
Skyhunter said:
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 apparently the climate principles where different then, like in the 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.
 
Last edited by a moderator:
  • #25
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.
 
  • #26
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 et al 2001.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.
 
  • #27
Saul said:
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 ?
 
  • #28
Saul said:
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.
 
  • #29
vanesch said:
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 Earth'shine 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.
 
  • #30
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.
 
  • #31
Saul said:
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.
 
  • #32
Saul said:
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.
 
  • #33
vanesch said:
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 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 (PMIP) and Paleoclimate Modelling Intercomparison Project Phase II (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 [thread=307685]Estimating the impact of CO2 on global mean temperature[/thread] 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
 
  • #34
sylas said:
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.
 
  • #35
vanesch said:
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) "ftp://eos.atmos.washington.edu/pub/breth/papers/2006/Bony_etal_feedbacks.pdf"[/URL], in [i]Journal of Climate[/i], Vol 19, 1 Aug 2006, pp 3445-3482.[/list]

    [QUOTE]
    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.
    [/QUOTE]

    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.

    [QUOTE]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.[/QUOTE]

    Quite so.

    Cheers -- sylas
 
Last edited by a moderator:

Similar threads

  • Earth Sciences
Replies
17
Views
7K
Replies
1
Views
2K
Replies
2
Views
153
Replies
2
Views
9K
  • STEM Academic Advising
Replies
5
Views
2K
Replies
20
Views
6K
  • STEM Academic Advising
Replies
2
Views
1K
Replies
9
Views
2K
  • General Discussion
Replies
8
Views
3K
  • Special and General Relativity
Replies
11
Views
1K
Back
Top