Global warming is not caused by CO2

In summary, a recent report published in a scientific journal argues that climate warming is a natural and unstoppable process, and that carbon dioxide is not a significant contributor. The authors suggest that solar variability and other natural factors better explain observed temperature changes. They also criticize current legislation that aims to control greenhouse gas emissions, stating that it is ineffective and costly. The authors' research suggests that cosmic rays and the solar wind may play a larger role in climate change than previously thought. However, some remain skeptical of their hypothesis and believe that reducing pollution is still important regardless of its impact on global warming. Overall, the debate surrounding climate change highlights the tendency for humans to seek patterns and fear the unknown.
  • #36
Integral said:
Let me restate that if DR. Wood had more confidence in his results he would have used a stronger word then doubtful.

Happy Bystander?

Preachers and politicians make absolute statements. Real scientists tend to qualify what they say because they realize they do not have perfect knowledge. Historically "scientists" who claim certainty about whatever they are selling have been attempting to con people into giving them money, particularly for medical treatments.
 
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  • #37
reasonmclucus said:
Preachers and politicians make absolute statements. Real scientists tend to qualify what they say because they realize they do not have perfect knowledge. Historically "scientists" who claim certainty about whatever they are selling have been attempting to con people into giving them money, particularly for medical treatments.

Richard Muller agrees:

http://www.technologyreview.com/Energy/13423/page2/

In most fields of science, researchers who express the most self-doubt and who understate their conclusions are the ones that are most respected.
 
  • #38
I am offended by the notion that global warming can be ameliorated by the puchase and sale of "carbon credits." If CO2 has nothing to do with global warming, this practice is particularly noxious. But even if CO2 has everything to do with global warming, it is still just a shell game to shuffle wealth from one place to another, without any true discernable benefit to mankind. I do not understand why scientists around the world have not risen up and publicly decried the promulgation of carbon credits.
 
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  • #39
Bystander said:
Three hundredths of a percent in solar output corresponds to a 20 mK change in Earth surface temperature. That's over 20 years, and includes no discussion of instrument drift, or measures to correct for instrument drift. Polar "melting" on Mars? Over seven (?) years (I ain't going to reread that one for this post) isn't a long enough time frame to say anything.

As rebuttals of the IPCC arguments these papers are as strewn with bad science as the IPCC --- concatenations of unstated, implicit "if" statements that go on for a half dozen to dozen logical steps to reach meaningless conclusions.

Science is about unambiguous tests of single "if" statements.

It looks to me that it is more like 0.1% change in intensity with a period of about 10 years.

Solar-cycle-data.png


The change in temperature over the century is about 0.2% (measured in Kalvin). It is believed that solar irradiance is not the only way the sun influence the Earth's climate. The solar wind is believed to increase the number of cloud concentration nuclei's. Some people believe that this effect will have a greater effect on the climate then the changes in solar irradiaiance.
 
  • #40
pitot-tube said:
The fact that the temperature in the Pacific ocean has a 10 year cycle that superimposes itself on the 3-5 year El Nino cycle suggests to me that variation in solar output does not account for changes in global temperature - there is something else going on.
No one has found a 10 year cycle for cosmic ray output that is superimposed on a 3-5 year cycle for cosmic ray output.
And why did the sun suddenly change its output to start the current ice age hot/cold cycle when it hadn't done so billions of years before?
Thousands of measurements have been done over land and sea to check the output of heat from the Earth's interior and this is too small compared to the Sun's output of energy to make a difference.
If the concentration of dissolved substances in the oceans had decreased then the amount of water vapour and other gases could increase in the atmosphere accounting for some global warming - but this is not the case:ther is no evidence of a change in concentration of dissolved substances.
As far as I can see the likely answer to the global warming conundrum is also one that accounts for the local warming in the pacific ocean and for both el nino and the pacific decadal oscillation.In this scenario there is an increase in greenhouse gas emission from the ring of fire - the volcanoes beneath the pacific ocean.One part of the ring of fire is causing heating for 3-5 years and the other for 10 years.El nino starts with high pressure off the coast of south america.Gas emitted from under the sea in the area of central america would be carried on the prevailing wind to the south and central pacific causing warming and high pressure there.The pacific decadal oscillation could start elsewhere on or close to the ring of fire.The jetstream can be shifted by warming in the pacific and thousands of years ago this would have resulted in warm weather in ice bound places in the north, and could have caused the rapid emission of icebergs from north america into the atlantic.Something caused the ice age (which we are still in) and people were not around at the time, so whatever caused global cooling is natural and it is therefore likely that whatever caused global warming is too.It should be kept in mind that in any explanation of the cause of el nino/the pacific decadal oscillation there also needs to be an explanation of why the warming effect goes away and then comes back.I think it is important to challenge the computer whizz kids with their hugely complicated models that say phenomena like el nino have no single cause but result from innumerable feedback mechanisms from sea and air currents on a global scale.Why shouldn't something local cause El Nino? Or the pacific decadal oscillation?
The Earth is rising more in the northern hemisphere than in the south (so I've heard - not from my hairdresser though!).Does this correspond with some sort of increased degassing of the mantle in the north - gas released as pressure is released?

That's interesting. I didn't realize that those two effects have the same period.
 
  • #41
sysreset said:
I am offended by the notion that global warming can be ameliorated by the puchase and sale of "carbon credits." If CO2 has nothing to do with global warming, this practice is particularly noxious. But even if CO2 has everything to do with global warming, it is still just a shell game to shuffle wealth from one place to another, without any true discernable benefit to mankind. I do not understand why scientists around the world have not risen up and publicly decried the promulgation of carbon credits.
Reducing pollution must necessarily have an associated cost; the study of minimizing these costs in a large society is economics. Being a scientist (physical) has gives one little qualification in the means of efficient reduction. Furthermore, free market pollution credits have a track record demonstrating superiority to central planning. The Acid Rain trading program began in 1995. See for example the http://www.epa.gov/airmarkets/progsregs/nox/index.html" [Broken].
 
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  • #42
We see higher temperatures as we see higher CO2 levels. And we conclude that the increase in temperature is due to GH effect of CO2, which is increasing due to human activities.
But this schema is basically supported by the fact that high CO2 levels were also present on warm or hot periods on Earth history.
What if high levels of CO2 are the consequence of high temperatures and not the cause?

It is known that CO2 competes with oxygen on the first step of the cycle by which plants are fixing CO2. At higher temperatures, plants implement different techniques including stopping fotosynthesis, as oxygen wins the competition. So, at higher temperatures, fotosynthesis would only work at higher CO2 levels.

In my opinion, ancient records of CO2 levels cannot proof that CO2 was the cause or the consequence of high temperatures.
 
  • #43
vivesdn said:
What if high levels of CO2 are the consequence of high temperatures and not the cause?

I agree. Correlation does NOT imply causation!
What's more, one would expect to the temperature lag behind the CO2 levels just a bit.
This is because rising concentrations of CO2 are said to cause cascading global warming.
Does anyone know if this lag effect is seen?
 
  • #44
gendou2 said:
I agree. Correlation does NOT imply causation!
What's more, one would expect to the temperature lag behind the CO2 levels just a bit.
This is because rising concentrations of CO2 are said to cause cascading global warming.
Does anyone know if this lag effect is seen?

It is in fact the CO2 which lags the temperature, with 600 years! That was first not seen, and hence the statement was made that it was the CO2 that caused directly the heating.
But now that the heating comes first, that couldn't hold anymore. So now the given explanation is that the initial cause of the heating was not the CO2 but something else (solar irradiance or something), but that through feedback, this caused higher CO2 levels (indeed, that's the causal link: heat -> CO2 and not the original CO2 -> heat), but that the CO2 then took over and amplified the original heating by greenhouse effect.
 
  • #45
vanesch said:
It is in fact the CO2 which lags the temperature, with 600 years! That was first not seen, and hence the statement was made that it was the CO2 that caused directly the heating.
But now that the heating comes first, that couldn't hold anymore. So now the given explanation is that the initial cause of the heating was not the CO2 but something else (solar irradiance or something), but that through feedback, this caused higher CO2 levels (indeed, that's the causal link: heat -> CO2 and not the original CO2 -> heat), but that the CO2 then took over and amplified the original heating by greenhouse effect.

...at which point, according to the standard routine, I would kick in with this post, demonstrating that the characteristics of signals demonstrate that this feedback effect did not work, which basically refutes the idea that increased greenhouse effect causes significant heating.

For the visual stimulated / non-link clickers, this is the graph which illustrates that:

epica5.GIF
 
  • #46
Either way, too much carbon dioxide in our atmosphere doesn't bode well for us. If you don't believe me, look at Venus.
 
  • #47
LightbulbSun said:
Either way, too much carbon dioxide in our atmosphere doesn't bode well for us. If you don't believe me, look at Venus.

But what is too much? 380ppmv is 0.000380 atmosphere. Surface atmospheric pressure on Venus is 91 atmosphere with 95% CO2. So we are talking some 6 orders of magnitude here or a factor 227,5000. What would be the maximum ppvm if we burned all fossil fuels at the current rates and trend?

There is also that little hypothesis that convection -bringing heat to altitudes- causes significant changes in greenhouse radiative effects. On Earth convection is a major player (Hadley cell) while I linked earlier to studies that showed that convection was not a player in the lower levels of Venus atmosphere.
 
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  • #48
But what we all now know is that increasing levels of CO2 are not the cause but a consequence.

Thank you Andre, as I was suspecting that CO2 levels might follow Temperature increases and not the opposite. I thought that this was not possible to state or refute given the resolution with which these data can be obtained. But this chart is pretty clear.

This conclusion is partially good news: climate change does not depend on our CO2 production.
Bad news: what we can do then?
 
  • #49
vivesdn said:
But what we all now know is that increasing levels of CO2 are not the cause but a consequence.

Thank you Andre, as I was suspecting that CO2 levels might follow Temperature increases and not the opposite. I thought that this was not possible to state or refute given the resolution with which these data can be obtained. But this chart is pretty clear.

This conclusion is partially good news: climate change does not depend on our CO2 production.
Bad news: what we can do then?

I would say that the bad news is that we have allowed alarmists to mis-use science for political purposes. Problem is that eventual reality-refutal will expose that with very serious consequences for science. That's the singlemost biggest problem.

Second problem is that the energy conversion to 'renewables', which will be necesary, eventually will suffer serious drawbacks as well. As soon as the bubble bursts, we will be back to square one. If we had stimulated conversion to renewables (nuclear) the true and honest way, it would have been much slower but the end would not have been obscured.

Third problem is that bad science makes bad politics, if you're convinced that you'll only have so few years before climate armageddon, anything goes to prevent it. But that 'anything', like sequestring carbondioxide, may do nothing at significant costs.

Fourth: cap and trade programs may eventually end up in anti-Robin Hood effects, stealing from the poor to give to the rich.
 
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  • #50
There seems to be an extraordinary dissonance between the facts given in this thread and the facts given in Al Gore's documentary. How is this resolved? I am very hesitant to conclude in my own mind that anthropogenic CO2 emissions are either extremely dangerous or not dangerous at all.

Also, if CO2 is not a significant cause of anthropogenic global warming, what about other substances?
 
  • #51
gendou2 said:
There seems to be an extraordinary dissonance between the facts given in this thread and the facts given in Al Gore's documentary. How is this resolved? I am very hesitant to conclude in my own mind that anthropogenic CO2 emissions are either extremely dangerous or not dangerous at all.

Well, you probably know the routine: refute it, challenge Al Gore and me scientifically. Do everything possible to demonstrate one to be wrong. It's not that difficult.


Also, if C2 is not a significant cause of anthropogenic global warming, what about other substances?

Same story I would say, albeit that global and local effects both of CO2 and CH4 will be eye-openers in the first place, once examined thoroughly.
 
  • #52
Andre said:
But what is too much? 380ppmv is 0.000380 atmosphere. Surface atmospheric pressure on Venus is 91 atmosphere with 95% CO2. So we are talking some 6 orders of magnitude here or a factor 227,5000. What would be the maximum ppvm if we burned all fossil fuels at the current rates and trend?

There is also that little hypothesis that convection -bringing heat to altitudes- causes significant changes in greenhouse radiative effects. On Earth convection is a major player (Hadley cell) while I linked earlier to studies that showed that convection was not a player in the lower levels of Venus atmosphere.

I am not knowledgeable on the carbon dioxide threshold for humans.
 
  • #53
LightbulbSun said:
I am not knowledgeable on the carbon dioxide threshold for humans.

Agreed but that's not the point. The point is that there was a hypothesis about the relationship between greenhouse gasses and global temperature, which was defended in a rather unusual way as demonstrated by Bored Wombat.

But if it aint so, it aint so

http://icecap.us/images/uploads/GSA.pdf

In a Geological Society of America abstract, Dr. Don Easterbrook, Professor of Geology at Western Washington University, presents data showing that the global warming cycle from 1977 to 1998 is now over and we have entered into a new global cooling period that should last for the next three decades. He also suggests that since the IPCC climate models are now so far off from what is actually happening that their projections for both this decade and century must be considered highly unreliable...cont'd

So perhaps it's time for the politics considering how to retreat from the fight against a non-issue and stop shooting the messengers.
 
  • #54
LightbulbSun said:
I am not knowledgeable on the carbon dioxide threshold for humans.

Andre said:
Agreed but that's not the point. ...
I think LBS was asking about toxic levels of CO2 for basic human respiration? C02 is only a problem for respiration when it displaces the required oxygen, it is not otherwise toxic.
 
  • #55
  • #56
Human Respiration

The air that leaves a person's lungs during exhalation contains 14% oxygen and 4.4% carbon dioxide.

Atmospheres with oxygen concentrations below 19.5 percent can have adverse physiological effects, and atmospheres with less than 16 percent oxygen can become life threatening.

Source: Composition of Air

The Earth's atmosphere has 20.95% oxygen. So all it takes is a 1.4% reduction in oxygen to have adverse physiological effects on a human. My point is, an increase in CO2 presents a serious health risk, and it doesn't really matter whether it causes global warming or not.
 
  • #57
LightbulbSun said:
The Earth's atmosphere has 20.95% oxygen. So all it takes is a 1.4% reduction in oxygen to have adverse physiological effects on a human. My point is, an increase in CO2 presents a serious health risk, and it doesn't really matter whether it causes global warming or not.

But a reduction of 1.4% oxygen is 14,000 ppmv how would that relate to CO2 increases of 100-200 ppmv?
 
  • #58
Or put another way, given the current CO2 increases of ~15 ppmv per decade, it would take ~9000 years to reach 14000ppmv/1.4% CO2.
 
  • #59
Higher concentration of CO2 would also increase fotosynthesis and sea absorption.
Most of total carbon on Earth is stored in dolemite mountains and sediment layers.
 
  • #60
Andre said:
Well, you probably know the routine: refute it, challenge Al Gore and me scientifically. Do everything possible to demonstrate one to be wrong. It's not that difficult.Same story I would say, albeit that global and local effects both of CO2 and CH4 will be eye-openers in the first place, once examined thoroughly.

So far, no one has been able to establish one fact that is inconsistent with increased CO2 concentrations causing the average temperature of the surface of the Earth to increase, nor with the increased CO2 concentrations being generated directly or indirectly by human activity.

But that is not enough. To prove that the average temperature of the surface of the Earth is increasing due to concentrations of CO2 which result from human activity, one has to show that there are facts which are inconsistent with all other reasonable alternative explanations.

So what are those other reasonable alternative explanations? So far as I can tell, they are:

1. that the solar cycle is causing the Earth's surface to warm. In other words, the radiation energy output of the sun has increased.

2. that the increase in CO2 concentration is due to natural causes ie. causes which are not due to human activity, such as volcanic eruptions.

3. that the Earth is undergoing cyclical temperature change due to the change in the angle of the Earth to the sun due to precession of the Earth's axis of spin

4. that there is no increase in CO2 concentration at all. The problem is that the record keeping prior to the 1950's is poor and analysis of ice layers in glaciers is inaccurate.

Are there any others?

AM
 
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  • #61
mheslep said:
C02 is only a problem for respiration when it displaces the required oxygen, it is not otherwise toxic.
I don't think that is correct. CO2 is absolutely toxic at concentrations over 5%. This is not due to displacement of O2 (humans can breathe if the oxygen level is 16%). It is due to acidification of the blood and tissues (acidosis) which becomes a problem at CO2 levels of about 1.5% according to this article.

AM
 
  • #62
Andrew Mason said:
So far, no one has been able to establish one fact that is inconsistent with increased CO2 concentrations causing the average temperature of the surface of the Earth to increase,

You mean like this?

monthlyco2vstemps.jpg
 
  • #63
explanation needed for newbie:

Conclusion is clear but I would like to learn about Hadley and MSU temperatures.
 
  • #64
vivesdn said:
...Conclusion is clear but I would like to learn about Hadley and MSU temperatures.

Hadley is the British Met Office producing monthly temperature series here. http://www.cru.uea.ac.uk/cru/data/temperature/hadcrut3vgl.txt [Broken] is the global set.

The first row in the year is monthly temperatures, the second is percentage of the globe covered.

http://www.ssmi.com/msu/msu_data_description.html produces monthly temperature data through the atmosphere as processed by satellites, the http://www.ssmi.com/msu/msu_data_description.html#msu_weighting_functions obviously, being relevant:

sc_Rss_compare_TS_channel_tlt.png
 
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  • #65
Andrew Mason said:
So far, no one has been able to establish one fact that is inconsistent with increased CO2 concentrations causing the average temperature of the surface of the Earth to increase, nor with the increased CO2 concentrations being generated directly or indirectly by human activity.

I hope it's not too much of a trouble but could you give an example anywhere in the past what supports that statement:
increased CO2 concentrations causing the average temperature of the surface of the Earth to increase.

It may look like a redundant question, since not a day will go by or you'd catch phrases like this somewhere. But which data sets exactly would support that?

So what are those other reasonable alternative explanations? So far as I can tell, they are:

...

Are there any others?

Albedo variation mainly due to cloud cover, see this post

Not too bad, it seems, for two decades:

albedo-temp.GIF


Note that in the top graph the Y-axis both depicts the variation in albedo in percentage and the temperature variation in tenth of degrees Kelvin.
 
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  • #66
Andrew Mason said:
I don't think that is correct. CO2 is absolutely toxic at concentrations over 5%. This is not due to displacement of O2 (humans can breathe if the oxygen level is 16%). It is due to acidification of the blood and tissues (acidosis) which becomes a problem at CO2 levels of about 1.5% according to this article.

AM
Yes I expected that at some absurdly high level CO2 would be toxic; even water is toxic at some point. But I (incorrectly) believed that lack of O2 from displacement would always be the more immediate problem. At least for enclosed space where the CO2 slowly replaces O2 consumed by respiration or combustion, apparently the CO2 will grow toxic before the onset of suffocation. Of course if you are suddenly immersed in a CO2 cloud (e.g. volcanic release) the lack of O2 will cause suffocation first.
http://vulcan.wr.usgs.gov/Glossary/Lakes/description_volcanic_lakes_gas_release.html
 
  • #67
Andre said:
I hope it's not too much of a trouble but could you give an example anywhere in the past what supports that statement.
Perhaps I should have said that there is no fact that is generally accepted as proven fact, that is inconsistent with the observed average increase in global temperature being due to human activity.

It may look like a redundant question, since not a day will go by or you'd catch phrases like this somewhere. But which data sets exactly would support that?
It is a matter of the absence of proven facts contradicting the stated hypothesis ie. that global temperature increase is being caused by human activity.

Note that in the top graph the Y-axis both depicts the variation in albedo in percentage and the temperature variation in tenth of degrees Kelvin.
Yes. I could add the albedo effect as a separate explanation for global warming. The only problem is that a signficant change in albedo effect can be a mechanism that affects global temperature but it is merely a symptom of an underlying cause. A significant change in albedo effect begs the question: what is causing it? If it is the loss of polar ice, which is in itself caused by global increase in temperature due to increase in CO2 concentration, albedo effect is not the primary cause.

BTW, I am not so sure that your graphs are correct. As you point out, the greatest albedo effect appears to be cloud cover. This article suggests that the cloud albedo effect is INCREASING despite general global temperature increase.

AM
 
  • #68
Andrew Mason said:
Perhaps I should have said that there is no fact that is generally accepted as proven fact, that is inconsistent with the observed average increase in global temperature being due to human activity.

It is a matter of the absence of proven facts contradicting the stated hypothesis ie. that global temperature increase is being caused by human activity.

You have a curious view about the onus of proof. The (necesary) elements of the hypothesis in question are:

1. CO2 and CH4 are greenhouse gasses,
2. greenhouse gasses are the main cause for the atmosphere to be warmer than grey body temperature.
3. increases concentration of greenhouse gasses increase the temperature of the atmosphere significantly, (global warming).
4. humans increase the concentration of greenhouse gasses.
hence humans cause global warming

There is little reason to challenge elements #1 and #4, but how about #2 and #3? If those were to be true then variations in greenhouse gasses in the past would necesarely lead to corresponding changes in global temperatures. So whether or not that evidence is there, should be decisive for the confirmation or falsification of those elements #2 and #3.

So how about that proof?


albedo effect is not the primary cause.

Albedo variation is only a link in the chain of causes and effects. Variation in cloud cover may have many causes, not necesarily warming.

BTW, I am not so sure that your graphs are correct. As you point out, the greatest albedo effect appears to be cloud cover. This article suggests that the cloud albedo effect is INCREASING despite general global temperature increase.

AM

Now, isn't that a coincidence? We're talking about the same source! However, what Pallé et al (2006) failed to verify, is the correlation between their results and the global temperatures. They just erroneously assumed that the temperatures continued to rise, perhaps because that's what you hear all the time.

See also this thread
 
  • #69
Andre said:
You have a curious view about the onus of proof. The (necesary) elements of the hypothesis in question are:

1. CO2 and CH4 are greenhouse gasses,
2. greenhouse gasses are the main cause for the atmosphere to be warmer than grey body temperature.
3. increases concentration of greenhouse gasses increase the temperature of the atmosphere significantly, (global warming).
4. humans increase the concentration of greenhouse gasses.
hence humans cause global warming
All that is needed for a successful hypothesis is an explanation that is rational, plausible and that is not inconsistent with any facts.

In this case, it can be shown that CO2 absorbs infrared radiation and is, therefore, capable of causing the surface of the Earth to become warmer(1). It can also be shown that humans directly add about 30 GT of CO2 to the atmosphere annually (4). The total mass of CO2 in the atmosphere at present is about 3,000 GT which results in a CO2 concentration of 383 ppm by volume. So the addition of 30 GT could add as much as an additional 1% or almost 4 ppm to the CO2 concentration of the atmosphere. So the explanation is rational and plausible.One merely has to show that there are no proven facts that conflict with the hypothesis.

So my question is: what facts is this hypothesis inconsistent with?

As I said, however, this does not make it the correct explanation. One would need to look at all other alternate explanation and see if there are facts which conflict with them. Only by eliminating all other hypotheses with proven facts can one reach a reasonable conclusion that a hypothesis is correct.

There is little reason to challenge elements #1 and #4, but how about #2 and #3? If those were to be true then variations in greenhouse gasses in the past would necesarely lead to corresponding changes in global temperatures. So whether or not that evidence is there, should be decisive for the confirmation or falsification of those elements #2 and #3.
Having established a rational and plausible explanation, one does not have to directly prove your points 2 and 3. Your question really is" do variations in greenhouse gas concentrations in the past (assuming there is a consensus that these variations are proven) conflict with points 2 and 3?". I don't think there is a consensus that they do.

Albedo variation is only a link in the chain of causes and effects. Variation in cloud cover may have many causes, not necesarily warming.
Agreed.

Now, isn't that a coincidence? We're talking about the same source! However, what Pallé et al (2006) failed to verify, is the correlation between their results and the global temperatures. They just erroneously assumed that the temperatures continued to rise, perhaps because that's what you hear all the time.

See also this thread
Are you saying that average global temperature is not increasing?

AM
 
  • #70
Andrew Mason said:
All that is needed for a successful hypothesis is an explanation that is rational, plausible and that is not inconsistent with any facts.

In this case, it can be shown that CO2 absorbs infrared radiation and is, therefore, capable of causing the surface of the Earth to become warmer(1). It can also be shown that humans directly add about 30 GT of CO2 to the atmosphere annually (4). The total mass of CO2 in the atmosphere at present is about 3,000 GT which results in a CO2 concentration of 383 ppm by volume. So the addition of 30 GT could add as much as an additional 1% or almost 4 ppm to the CO2 concentration of the atmosphere. So the explanation is rational and plausible.One merely has to show that there are no proven facts that conflict with the hypothesis.

So my question is: what facts is this hypothesis inconsistent with?

As I said, however, this does not make it the correct explanation. One would need to look at all other alternate explanation and see if there are facts which conflict with them. Only by eliminating all other hypotheses with proven facts can one reach a reasonable conclusion that a hypothesis is correct.

Indeed. What you write is the difference between what I like to call suggestive evidence (sure there is !) and conclusive proof, and what annoys me is that the first is presented as the second. There's a big difference between both on the scientific side. In the second case, it becomes almost ridiculous to contest the statement, while in the first case, a critical analysis is due, and by flipping too fast from the first to the second, one could make a big mistake and "lock it in".

I would say that the biggest problem facing "CO2 is the sole drive for AGW and this will lead to dramatic increases in temperature" as a definitive statement is that there is no ab initio model, purely based upon physically known facts (with no fitting parameters) that numerically predicts correctly all the main quantities involved.

Indeed, there's no discussion that CO2, in a static atmosphere, acts as a greenhouse gas, but that effect, by itself, is about 0.8K per CO2 doubling. Even adding the important water vapor feedback fully, one arrives at 1.5K per CO2 doubling. That is, for a static atmosphere, in which there is no convection (which cools), and without doing anything to the Earth surface except keeping the water vapor pressure as given by the surface temperature. But AGW proponents say that this must be between 1.5 and 6 K, with a preferred value around 3 K.
So the purely physical effect we know about CO2 is simply not strong enough to explain the larger effect needed for a dramatic AGW.

That doesn't mean that there cannot be positive feedback mechanisms, but these mechanisms are hence the essential point of the AGW thesis, and they have not been modeled ab initio, but at most they are *fitted* to some data in which one took *already* the hypothesis that the drive was CO2. These are much more difficult issues and the system is much more complicated than just "CO2 is a greenhouse gas, and if we put more in the atmosphere, it will get hotter". The essence of the AGW theory is based upon ununderstood feedbacks which have not been modeled.
That doesn't mean they don't exist of course, and that doesn't mean that AGW is wrong. But it means that it is not "a rational plausible explanation that is not in contradiction with the facts". It is a totally hypothetical phenomenon that needs to be introduced *in order* for CO2 to be the sole culpritt.
 

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