Climate sensitivity- lowering the IPCC "fat tail"

By Dr. Pat Michaels at World Climate Report

A new, lower estimate of climate sensitivity

There is word circulating that a paper soon to appear in Science magazine concludes that the climate sensitivity—how much the earth’s average temperature will rise as a result of a doubling of the atmospheric concentration of carbon dioxide—likely (that is, with a 66% probability) lies in the range 1.7°C to 2.6°C, with a median value of 2.3°C. This is a sizeable contraction and reduction from the estimates of the climate sensitivity given by the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), in which the likely range is given as 2.0°C to 4.5°C, with a best estimate of 3.0°C.

Further, the results from the new analysis largely eliminate the “fat tail” of the distribution of possible values of the climate sensitivity (that the IPCC AR4 report was fond of) which included the possibility that very large climate sensitivities are a realistic possibility. In the new paper, the authors find only “vanishing probabilities” for a climate sensitivity value greater than 3.2°C and that values greater than 6.0°C are “implausible.”

Contrast that with the IPCC assessment of the literature (summarized in our Figure 1) which routinely includes studies concluding there is a greater than a 10% possibility that the true climate sensitivity exceeds 6°C and some which find that there is a greater than 5% possibility that it exceeds 10°C.

Figure 1. Climate sensitivity distributions retained (and in some cases recast) by the IPCC from their assessment of the literature. Note the “fat tail” towards the right which indicates the possibilities of the climate sensitivity having a very large positive value (that is, a huge degree of global temperature rise for a doubling of the atmospheric carbon dioxide concentration) (source: IPCC AR4).

The new paper, from a team of researchers led by Andreas Schmittner of Oregon State University, throws cold water on the IPCC’s tails. Here is its rather provocative abstract:

Assessing impacts of future anthropogenic carbon emissions is currently impeded by uncertainties in our knowledge of equilibrium climate sensitivity to atmospheric carbon dioxide doubling. Previous studies suggest 3 K as best estimate, 2–4.5 K as the 66% probability range, and non-zero probabilities for much higher values, the latter implying a small but significant chance of high-impact climate changes that would be difficult to avoid. Here, combining extensive sea and land surface temperature reconstructions from the Last Glacial Maximum with climate model simulations we estimate a lower median (2.3 K) and reduced uncertainty (1.7–2.6 K 66% probability). Assuming paleoclimatic constraints apply to the future as predicted by our model, these results imply lower probability of imminent extreme climatic change than previously thought.

Figure 2 shows the distribution of the range of the earth’s probable climate sensitivity as determined by Schmittner et al. Note the rapid drop-off in the probability that the climate sensitivity is much greater than 3°C (the IPCC “best estimate” for the sensitivity), and that the distribution falls off less slowly towards the left (towards lower sensitivity) than towards the right (higher sensitivities). The “fat right-hand tail” of the distribution is gone and the possibility that the climate sensitivity is in the 1°C to 2°C range is not minimal.

Figure 2. Distribution of the land/ocean climate sensitivity as determined by Schmittner et al. (adapted from Schmittner et al., 2011).

The Schmittner et al. results join a growing number of papers published in recent years which, by employing investigations of the earth’s paleoclimate behavior (that is, how the earth’s temperature changes in the past when subject to changing climate forcings) have come to somewhat similar conclusions, especially regarding the (lack of) evidence to support the existence of the fat right-hand tail.

For example, researchers James Annan and Julia Hargreaves published a paper in 2009 that concluded many of the assumptions underlying the possibilities of very high climate sensitivities were unjustified. They wrote:

When instead reasonable assumptions are made, much greater confidence in a moderate value for [the climate sensitivity] is easily justified, with an upper 95% probability limit for [the sensitivity] easily shown to lie close to 4°C, and certainly well below 6°C. These results also impact strongly on projected economic losses due to climate change.

Annan made repeated comments during the IPCC AR4 review process that the IPCC’s handling of climate sensitivity and its probability distributions were incorrect. His complaints largely fell upon deaf ears.

However, as there are appearing more and more examples in the literature, of which Schmittner et al. is one of them, making a convincing case that the very high climate sensitivities are not defendable, there will be growing pressure on the IPCC in its Fifth Assessment Report to greatly shrink the fat tail of the probability distribution for the true climate sensitivity. However, the climate “realists” very bad experience with the last IPCC process makes them chary. James Annan, writing at his blog in reference to the new Schmittner et al. paper had this to say as to what may result from it:

That said, [the Schmittner et al. paper] is a useful antidote to the exaggerated uncertainty estimates that have been prevalent over recent years, and I certainly applaud the intentions and effort underlying this substantial piece of work. In any case, I expect the merchants of doubt to do their worst on it when they cite it in the IPCC report.

But, as the evidence mounts against a high value for the climate sensitivity, and evidence grows for a low value (recall that the observed rate of global warming for the past several decades has fallen well below IPCC best estimates), the IPCC is going to be hard-pressed to retain the status quo in its Fifth Assessment Report, especially in light of the enhanced scrutiny that its AR4 misdeeds brought upon the process.

But, as James alludes to, perhaps we ought not be holding our breath.

And, for those keeping score out there, about 10 years ago, a couple of us here at WCR were part of a team which published a paper in the journal Climate Research in which we employed a variety of techniques to derive empirical estimates of the amount of temperature rise that we could expect by the end of this century—a rise that could pretty well be considered to be in-line with the climate sensitivity. We concluded that the expected temperature rise between 1990 and 2100 would be in the range 1.0°C to 3.0°C with our best guess being 1.8°C (in contrast to the IPCC estimates, which, at the time, were for a rise of between 1.4°C and 5.8°C).


Annan, J.D., and J.C. Hargreaves, 2009. On the generation and interpretation of probabilistic estimates of climate sensitivity. Climate Change, 104, 423-436, doi:10.1007/s10584-009-9715-y,

Michaels, P.J., P.C. Knappenberger, O.W. Frauenfeld, and R.E. Davis, 2002. Revised 21st century temperature projections. Climate Research, 23, 1-9.

Schmittner, A., et al., 2011. Climate sensitivity estimated from temperature reconstructions of the Last Glacial Maximum, Science, in press*,

*According to the authors


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This, from the laest Ecologist rather complements the above…
“Durban climate summit: is it time to forget about 2 degrees of warming?”


I guess we’ll have to wait to see how they come to this number, but it doesn’t sound like there’s much in the way of negative ‘feedback’ from water/clouds. It’s a nod in the literature in the direction of something at least sane, I suppose, but I hope certain quarters won’t be expecting this to be some sort of compromise figure that all reasonable people can settle on as a basis for CO2 control policy.


Wow! If true this is real dynamite for us “luke-warmists”. We now have real amunition against the extreme alarmist views.

Superimposing natural oscillations on the 350 year rising trend in the CETs of 0.25C/century and keeping that upward trend going
for another 150 years, calculations show significant drop in temperatures:
If the past rising trend isn’t kept going projected drop in temperatures due to natural oscillations could be much greater.

Scott Covert

They left out the possibility that CO2 might have a cooling effect. Still working from the old assumptions using models that don’t work.
But thanks for your input fellas.


Five stages of death: Bargaining.


“It is plausible to be skeptical of a number of issues regarding the findings of IPCC WG1. However, whether atmospheric gases such as CO2 (and H20, CH4, and others) warm the planet is not an issue where skepticism is plausible” ….Judith Curry
The real debate is about ‘feedback;. Current predictions of climate catastrophe due to human influence all depend on the assumption of a positive feedback effect, such that adding a little more CO2 to the atmosphere will cause a runaway greenhouse effect. This is pure speculation. We have never witnessed such an effect in geological history although past temperatures have been much higher and CO2 levels have been much higher. This positive feedback, reflected in ‘climate sensitivity’, is not based on experiment nor observation. It remains an unfounded conjecture in conflict with all known observations.
Some scientists believe that water vapour also produces a negative feedback because the increased albedo of the consequent extra cloud cover will reflect more solar radiation back to space. This may or not be the case, but what we do know is that about 8000 years ago, when temperatures were much hotter than now (up to 7 deg. Celsius hotter according to the IPCC Arctic Impact Assessment Report – Section 2.7), we saw no positive feedback, no runaway greenhouse effect and temperatures eventually fell. Estimates of climate sensitivity are pure speculation in conflict with all known observations. We have never seen a runaway greenhouse effect on this planet even though temperatures have been much higher and CO2 levels have been much higher in the past. The relative stability of our climate over millions of years suggests that if there is a climate feedback effect, it is a negative one. Unfortunately, in the field of climate prediction, Science based on careful observation and experiment has been replaced by computer modelling and speculation.

Leon Brozyna

Before you know it, they’ll be saying that whatever effect there is from greenhouse gases is too small to separate from the noise.


Post Normal Science?


In two years it will be reduced to maybe 0.5 to 1C, after that AGW will be dead and I hope half these clowns will be fired.

I have my doubts about all that. It has no sense to say we are 0.6 deg C warmer than in pre-industrial times, assuming the whole warming was caused by CO2, and then we project the curve up to 2100. 1980 ties were comparable or even colder than 1900s, 1940s were almost as warm as 2000s, MWP was warmer than present, even most of the interglacial was warmer than present. Recent warm peak was caused by natural oceanic variations, maybe combined somehow with the Sun activity. Since the most sensitive /polar/ areas show no relation with CO2 rise at all, all that sensitivity guesswork is nonsense.


How about prosecuted?

G. Karst

Holy Thermometers Batman!
Considering climate sensitivity is the very crux of the CO2 CAGW argument, this is a huge step forward, in the enabling, of useful discussion. Could we be seeing a merging of skeptical Vs warmist opinion??
Now if only something could be published, which gives us some confidence in the + or – sign, or that it is even constant in any direction. GK


Andrew says:
November 9, 2011 at 12:17 pm
“In two years it will be reduced to maybe 0.5 to 1C, after that AGW will be dead and I hope half these clowns will be fired.”
Agree. But first it will be changed to varying dynamically between -1.0 to +1.0 (or so), dynamically, and then forgotten. The “clowns” you mention, will be science advisors for some president, or in the high echelons of the UN, governing some new scare.

Werner Brozek

“In the new paper, the authors find only “vanishing probabilities” for a climate sensitivity value greater than 3.2°C and that values greater than 6.0°C are “implausible.” ”
I am sure this has a lot to do with what has happened over the last several years.
I have two multiple choice questions that I would like answers for if anyone has them: (Thank you in advance!)
1. What period of time must elapse before the time is significant with respect to climate trends or even the lack of any trends?
A. 10 years
B. 13 years
C. 15 years
D. 17 years
E. 20 years
F. None of the above
2. What must the slope be in order for the warming/cooling to be considered NOT significant?
A. Less than +/- 0.002 C/year
B. Less than +/- 0.004 C/year
C. Less than +/- 0.006 C/year
D. Less than +/- 0.008 C/year
E. Less than +/- 0.010 C/year
F. None of the above


The sad thing is that its now way to late for any chance of ‘climate science ‘ to gain a reputation for being sensible , far to many lies , far to many chicken little calls and far to much religiosity for people to forget . Its not water under the bridge because there was so much water it washed the bridge away. Now its question of cleaning up the mess and building a new bridge .


An interesting issue will be the prior (if any) used in the new assessment. Annan and Hargreaves were critical of the nature of this (and some adjustments made) by IPCC in their 2009 paper.

the IPCC is going to be hard-pressed to retain the status quo in its Fifth Assessment Report
Not so. From IPCC Report AR5, July 2015, para 2.7.1 3: “There have been estimates of a lower climate sensitivity (Schmitter et al 2011, …) but there are some ambiguities and they remain controversial.”. There is no other reference to it in the report.
Sorry I can’t provide the link, I should have it in a few years’ time.

Bill Illis

Determining the CO2 climate sensitivity from the conditions of the Last Glacial Maximum depends completely/100% on what your assumptions/calculations are for how much additional solar radiation is reflected away from the Earth by all that extra glacial ice, snow, desert and grassland and other changes in clouds and dust for example.
Climate science consistently downplays this impact and assumes something like just 1.0% more sunlight is reflected. (29.8% reflected today versus 30.8% at the Last Glacial Maximum). This 1.0% assumption magically gives one 3.0C per doubling from CO2. None of these papers actually tell you they are assuming 1.0% more sunlight is reflected (because it is built into a climate model simulation and because is so preposteriously low) but that is what they are using.
This study uses exactly the same assumption in the same kind of climate model simulation and, consequently, I put no stock into it.

Don Keiller

Progress indeed.
Last year this would not have got by the “gatekeepers”.
The backpeddling by high-impact journals is underway.


So if a climate model simulation gives a lower value of climate sensitivity (here Schmittner, 2011) the results of GCMs are welcomed? If yes, the next question would be: Why is the GCM used by Schmittner more reliable than other GCMs predicting higher values?

Arfur Bryant

I agree this is a step in the right direction, but…
This is still a paper based at least partially on model assumptions.
Observed data tells us this:
1. Since 1850 atmospheric CO2 has increased by about 40%.
2. Since 1850 the global temperature (insofar as it can be measured) has increased by about 0.9 K (HADCrut). (1850 is the date quoted by the IPCC as the start of accurate temperature data recording.)
There is no conclusive causation between the two statements 1. and 2.
Even if ALL the temperature increase was due to CO2, the linear progression would indicate a climate sensitivity of 2.25 K. This is essentially the same as the Schmittner et al median.
There is no observed acceleration in global warming, so a linear progression is at least fair.
However, we cannot attribute ALL the warming to CO2 because that would require us to deny that natural variability exists in any form.
So, all we can say is that SOME of the 0.9 K warming MAY have been caused by CO2.
This means the climate sensitivity is likely to be lower than 2 K, maybe significantly so.
Unfortunately, since no-one can say with any certainty how much of the Greenhouse Effect is contributed by CO2, any estimates, particularly those based on model assumptions, remain dressed-up guesses.
I agree with other posters that the near future will see further reductions in the estimates of CS.

Carl Chapman

Even 2.3 C per doubling is way out there. I think it’s more like 0.3 C. How does 2.3 C fit in with 0 warming since 1998 while CO2 increase is at the highest ever? There must be some very big negative effect exactly matching the CO2 effect.

Septic Matthew

Is the link to the original correct? I can’t find the paper.

Bruce of Newcastle

M.A.Vukcevic says:
November 9, 2011 at 11:55 am
Vuk – I agree, although I came at it from the solar cycle length aspect, using Butler and Johnston’s trend line for Armagh, which is similar to the CET in climate and latitude.
I might add that using Butler & Johnston 1996 with the CET gives you a climate sensitivity by difference of roughly 0.7 C/doubling, ie similar to Lindzen & Choi 2011 and nowhere near Schmittner et al’s value.
In other words the world is not going to fry because of CO2, carbon tax or no carbon tax (sigh).


1.7c to 2.7c is still way too high. These figures are still based on the erroneous assumption that backscattered LWIR has the same effect over oceans as it does over land. Black body calculations are inappropriate for liquids that can evaporatively cool. A more realistic range would be 0.25c to 0.3c for a doubling of CO2 concentrations, and it may be decades before we see even that as the assumption of pre industrial levels of CO2 at 280ppm could well be incorrect.
My quick calculation for climate sensitivity from a previous thread –
Those doing the black body calculations claim around 1 degree of warming for a doubling of CO2 from pre industrial levels* without feedback. However Earth is not a black body. 71% of the surface is ocean.
So divide that 1 degree of warming into two parts. 0.29 degrees for land and 0.71 degrees for oceans.
Now multiply 0.71 by 0.3 to get the realistic effect of backscattered LWIR on water that is free to evaporatively cool. (missing heat Kevin?)
Add this 0.213 degrees back to the 0.29 degrees for land to get 0.503 degrees of warming for a doubling of CO2.
Now multiply that 0.503 degrees by 0.5 to account for negative water vapour feed back, giving 0.2515 degrees of warming for a doubling of CO2. (* ignoring issues such as dodgy pre industrial CO2 levels determined from ice cores with diffusion problems.)
Conclude that 0.2515 degrees of warming will be neither dangerous nor catastrophic.
Further conclude that with a CO2 sensitivity this low there are not enough known or projected fossil fuel reserves to burn to cause dangerous or catastrophic global warming.
Even if the initial 1c is taken as 1.2c, the figure for sensitivity is still only 0.3018c.
1.7c to 2.7c??? Not on this planet.

What amazes me in those probability density functions (pdf), both the older (fat tailed) ones and the present one here, the possibility of a total negative feedback is virtually excluded (ie impossible) in many of them. The pdf is zero below ~1°C.
How can one make such statements? Especially when speculation about fat tails at 5 °C or even more ..

corporate message

Carl, you remember that riff..

“Aerosols…like the corners of my mind
Misty water-colored memories
Of the way we were
Scattered pictures
Of the smiles we left behind
Smiles we gave to one another
For the way we were
Can it be that it was all so simple then
Or has time re-written every line ?
If we had the chance to do it all again
Tell me, would we? Could We ?
Memories maybe beautiful and yet
What’s too painful to remember
We simply choose to forget
So it’s the laughter we will remember
The way we were
The way we were

Roger Knights

Don Keiller says:
November 9, 2011 at 12:54 pm
Progress indeed.

Can we call it “Climate Progress?”
Anyway, it’s another arrow in the elephant.


>Re: Septic Matthew says:
>November 9, 2011 at 1:15 pm
>Is the link to the original correct? I can’t find the paper.
It seems as if the link to the original paper has been taken down (although a cached version of it may still be available from google). Probably the co-author that posted it realized the error in his ways–as Science magazine greatly frowns about posting “in press” papers before they appear in the Magazine.
-Chip Knappenberger
World Climate Report

Dave Springer

This is a perfect example of what lowers your google ranking. There’s not a bit of content in this article that is original for WUWT. It’s reproduced verbatim from another website. Google isn’t interested in rewarding copy & paste. It’s up to you of course to determine whether the tradeoff is worth it but this IS damaging to your search rank.

Chuck Nolan

Annan made repeated comments during the IPCC AR4 review process that the IPCC’s handling of climate sensitivity and its probability distributions were incorrect. His complaints largely fell upon deaf ears.
I doubt Donna will be surprised by the useless IPCC.

Dave S,
There is a quite highly rated political blog [I won’t name it because I don’t much care for the owner] that does nothing but allow commenters to post the title and intro paragraph to a news story. Readers can then click on the title for the original link, then comment on the story on the blog. It’s the ultimate cut ‘n’ paste blog, but it still gets good ratings from google.

Septic Matthew

Chip Knappenberger,
Thank you.
I suspected some such, because I know the policy at AAAS. But it was only one of my suspicions.

Paper still available for free download here…
Catch it while you can.

Stas Peterson

You can call it progress I guess. But the real temperature rise per doubling is still ten times too high. It is .2 -.4 degrees per doubling based on what the real empirical data says.
i still think taking an opinion poll of what the effect will be, is not only unscientific, it is STUPID !

R. de Haan

So that world renowned climate scientist Al Gore was a bit wide of the mark?

Dave Springer says:
November 9, 2011 at 1:51 pm

This is a perfect example of what lowers your google ranking. There’s not a bit of content in this article that is original for WUWT.

When I spent some time worrying about Google ranking and my Pame Smart page, I concluded Google worked in mysterious ways and kept changing them. I figure as long as enough references show up, it’s probably okay. I suspect that all the content free me-too and taunts comments dilute the key phrases anyway.
I just Googled |ipcc fat tail|
#1 is:
World Climate Report » A new, lower estimate of climate sensitivity
23 hours ago … Climate sensitivity distributions retained (and in some cases recast) by the IPCC from their assessment of the literature. Note the “fat tail” ……/a-new-lower-estimate-of-climate-sensitivity/ – Similar
#2 is just a repost of this (odd it scores higher than this page!):
Climate sensitivity- lowering the IPCC fat tail : Truth is Contagious
Reposted from:
-the-ipcc-fat-tail/. November 9, 2011 @ 2:32 pm. By Dr. Pat Michaels at World ……/climate-sensitivity-lowering-the-ipcc-“fat-tail”
#6 is:
Watts Up With That?
1 day ago … Climate sensitivity- lowering the IPCC “fat tail” … Further, the results from the new analysis largely eliminate the “fat tail” of the distribution of …
Even with Goggle deranking, it looks like people will find WUWT and some will bookmark it.
I also Googled |rossi e-cat mw| and sites like,, and scored higher than the recent WUWT page (#10).
Fair enough, though I’m not sure why got #3.


If someone could re-plot the slope through the original RSS data I think it would look virtually flat TLT. Me thinks the current slope is incorrect and is (artificially) there to support AGW:

Michael Larkin

At last! I now know what that “fat tail” business is referring to…

For some may be small, but for my graphs a major milestone. Some three years ago a linked [I] stat counter to all graphs I put on line. The stat counter just recorded 100.000.
The WUWT is by far the greatest contributor.
22:44:26 9 November 2011 Pageloads | Visits SELECTION OF GRAPHS
Today⇓ Yesterday⇓ This Month⇓Total⇓
243 270 2,685 100,005
100.000th visitor is from :
Portland, Oregon, United States ,
IP Address: Comcast Cable (
9 Nov 2011 22:39:54, Visit Length:28 seconds, Browser:IE 9.0,OS:WinVista,Resolution:1366×768

When climate scientists finally reach a unanimous decision that climate sensitivity is zero, we will have reached the truth.
Sometimes I think people forget we live in a medium of gas. Remember that stuff; gas? Expose it to the tiniest bit of heat and it lifts and separates.
Trying to heat gas in an open area is like trying to herd cats. And claiming that gas in an open area can “trap” heat? well……I suppose mankind has made sillier claims in the past. Falling off the edge of a flat Earth comes to mind.

John Trigge

According to Aussie politicians, the temperature change is irrelevant – at least, no-one can get any of the ones who voted in our onerous carbon tax to state ANY figure for what the tax will do for the World’s temperatures.
Actually changing the temperature or keeping it to below an x degree increase has become a side issue and the mantra of ‘a green energy future’ and ‘cutting pollution’ (meaning CO2) has taken on a life of its own.

Philip Bradley

Sensitivity derived from land minimum and maximum temperatures, which over estimate warming by a large amount and most of the actual warming due to increased early morning solar insolation.
Real sensitivity well below 0.5.

Paul Linsay

Scott Covert says:
November 9, 2011 at 11:55 am
“They left out the possibility that CO2 might have a cooling effect. Still working from the old assumptions using models that don’t work.”
Interesting that you should say that. The extra heating of the surface from increasing CO2 is due to the weak unsaturated lines in its spectrum absorbing more infrared from the surface. This only increases logarithmically with concentration(at least that’s the conventional wisdom). At the top of the atmosphere where the CO2 radiates energy into outer space there is no such restriction. It’s all done by the strong spectral lines. This means that doubling the CO2 will double the rate at which IR will be radiated into space. I have no idea if the models take this into account, but I’d be real surprised, more like shocked, if they didn’t.

Climate sensitivity is a stupid idea which assumes that carbon dioxide actually controls global temperature and that once you know what it is doing you know the future. There is abundant empirical evidence showing that it has not happened for a century and good reason to believe that it has no influence on global temperature whatsoever.
First, lets look at what temperature and atmospheric carbon dioxide have actually done.
The twentieth century began with a cooling that had started in 1880 and which came to an end in 1910. From 1910 to the beginning of World War II there was a period of warming that Bjørn Lomborg has attributed to the influence of solar activity. The war brought plunging temperatures and bitter cold which was over by the late forties.From the late forties until the appearance of the the super El Nino of 1998 the temperature went nowhere and just meandered a bit. Ground based temperature curves show a warming start in the late seventies which satellite temperature measurements simply cannot see. This is true of both UAH and RSS satellites that closely agree on that point. Nevertheless, this warming that was supposed take up the eighties and the nineties has been given the name of “late twentieth century warming.”
It is totally phony and makes Hansen’s 1988 claim that warming had started false. While there was almost a fifty year lack of warming from the end of the war till the appearance of the 1998 super El Nino carbon dioxide was relentlessly increasing.
To explain the lack of warming that this increase of carbon dioxide should have created warming advocates came out with the idea that large amounts of industrial aerosols formed by war production had suppressed that warming. There is only one problem with that excuse: the southern hemisphere cooled more than the northern hemisphere did but the aerosols were almost all released in the northern hemisphere.
Satellite temperature measurements show that the only real global warming within the last 31 years was a short spurt that started with the super El Nino of 1998. In four years it raised global temperature by a third of a degree and then stopped. It was caused by the large amount of warm water that the super El Nino had carried across the ocean. Warmth from it lingered, suppressed one of the cool La Nina phases of ENSO and created a six year warm period I call the twenty-first century high. ENSO itself did not return until the 2008 La Nina appeared and looks like we are back to normal again.
The step warming of 1998 to 2002 is responsible for the very warm first decade of our century but it was oceanic in origin and definitely not any greenhouse warming. There has not been any warming since then as the recent BEST temperature study indicates despite Richard Muller’s attempt to cover that up in a BBC interview. Their ground temperature measurements actually show that there was no warming for the last 13 years. This is the embarrassing ground truth. And what is more embarrassing yet is that carbon dioxide just keeps on going up at the same steady rate it has been doing it since the measurements began in the fifties.
Looking at that temperature history it hard for me to understand how anyone be serious about “sensitivity” and expect it to tell the future. On top of that we have observations of Ferenc Miskolczi who determined, using NOAA database of weather balloon observations, that the infrared absorbance of the atmosphere has not changed for 61 years. During that same period of time the amount of carbon dioxide in the air increased by 21.6 percent. This means that addition of this amount of carbon dioxide to the atmosphere had no effect on the absorption of infrared radiation by the atmosphere. No absorption, no greenhouse effect, case closed.


The closer these guys get to the reality that climate sensitivity to CO2 forcing is a small number the better. But honestly, how can the sensitivity be high in the face of stable or declining global temps in the last 10 to 15 years, during which time CO2 continues to rise without pause.
Common sense review of the Earth’s climate history, detailed by some above, tells us that the climate is insensitive to CO2 and is dominated by negative feedback. GW is real, AGW is a maybe, CAGW is hysteria.


Gotta love that consensus. This is definitely the biggest blow to CAGW I have seen in my 4 years of watching the debate. It even beats the “gate”. Would love to see a remake of Gore’s movie, perhaps with guest roles from the nobel laureate hobbit who writes for the NYT and jimmy hansen with some final words. “Inconvenient” is now actually a really fitting word in light of these new estimates.