BREAKING: IPCC AR5 report to dial back climate sensitivity

Update: the IPCC edifice is crumbling, see The state of climate science: ‘fluxed up’

See also Willis’ article One Step Forward, Two Steps Back, and Lomborg: climate models are running way too hot

This post will be a sticky for awhile, new posts will appear below it. – Anthony

Dialing Back the Alarm on Climate Change

A forthcoming report points lowers estimates on global warming

by Dr. Matt Ridley

Later this month, a long-awaited event that last happened in 2007 will recur. Like a returning comet, it will be taken to portend ominous happenings. I refer to the Intergovernmental Panel on Climate Change’s (IPCC) “fifth assessment report,” part of which will be published on Sept. 27.

There have already been leaks from this 31-page document, which summarizes 1,914 pages of scientific discussion, but thanks to a senior climate scientist, I have had a glimpse of the key prediction at the heart of the document. The big news is that, for the first time since these reports started coming out in 1990, the new one dials back the alarm. It states that the temperature rise we can expect as a result of man-made emissions of carbon dioxide is lower than the IPPC thought in 2007.

Admittedly, the change is small, and because of changing definitions, it is not easy to compare the two reports, but retreat it is. It is significant because it points to the very real possibility that, over the next several generations, the overall effect of climate change will be positive for humankind and the planet.

Specifically, the draft report says that “equilibrium climate sensitivity” (ECS)—eventual warming induced by a doubling of carbon dioxide in the atmosphere, which takes hundreds of years to occur—is “extremely likely” to be above 1 degree Celsius (1.8 degrees Fahrenheit), “likely” to be above 1.5 degrees Celsius (2.4 degrees Fahrenheit) and “very likely” to be below 6 degrees Celsius (10.8 Fahrenheit). In 2007, the IPPC said it was “likely” to be above 2 degrees Celsius and “very likely” to be above 1.5 degrees, with no upper limit. Since “extremely” and “very” have specific and different statistical meanings here, comparison is difficult.

Still, the downward movement since 2007 is clear, especially at the bottom of the “likely” range. The most probable value (3 degrees Celsius last time) is for some reason not stated this time.

Most experts believe that warming of less than 2 degrees Celsius from preindustrial levels will result in no net economic and ecological damage. Therefore, the new report is effectively saying (based on the middle of the range of the IPCC’s emissions scenarios) that there is a better than 50-50 chance that by 2083, the benefits of climate change will still outweigh the harm.


Above are excerpts of an article Dr. Ridley has written for the Wall Street Journal, who kindly provided WUWT with a copy.

Read the entire story here


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Well, yeah.


So basically the whole “Global warming thing” has been a tempest in a teapot.

Is there any information on what is a climate optimum? Is it better in the 2000’s than the 1970’s for example? Is is better warmer or cooler than now? If so by how much? And why?

Lil Fella from OZ

They weren’t wrong then??!

Steve Jones

They are putting an awful lot of effort into calculating these temp rises v. probability and none of it is via the scientific method. Their concern is to keep their gravy train rolling whilst distancing themselves from the more ridiculous projections that real world data is falsifying right now.
Let’s hope the IPCC falls off this tight-rope and soon.

so does this mean that Dr. Train Driver/engineer will be out of a job now 🙂


Since earlier projections of increases in extreme weather,ie, hurricanes and tornadoes etc, have not come to pass, I wonder how they will address that aspect.

It is ‘likely’ further studies are needed *cough*


The basic question for IPCC in a world that is cooling not only in temperature but also in attitudes towards them, is how to preserve their status and funding. So they must backpaddle a bit, to avoid the danger of being called activist alarmists. It is, however, a razorthin edge to walk along, with the abyss of oblivion and insignificance on the other side of the knife’s edge.
They may adopt the practical view that in order to keep themselves clothed, warm and well-fed, the vision of a boiling globe and a starving humanity must be pushed a bit into the background.

Claude Harvey

Self-interest is a powerful motivator. A tactical retreat is one thing; capitulation is quite another. Do not expect those who gain their fame and make their livings under the banner of “ANY effect man may have on the environment is BAD” to fold their tents and steal away into the night.

Adam Gallon

The shift will continue towards “Ocean Acidification”, “Loss of Diversity” and any other “measured impact” that can conceivably keep the gravy train rolling onwards.


no matter what , reality will out . Lets just hope the merchants of BS get to pay the price for all the years they been putting on a demonstration of world class arrogance and ignorance


In reality, the warming must be <0.1K; easy to demonstrate when you cut the 'mistakes' out of Climate Alchemy. The worst of these is in 1981_Hansen_etal.pdf.
Para 2: the claim that CO2 inhibits IR to space in the range 7 – 14 microns is untrue (a bit around 10 microns). Later on they went for 15 microns which is true but easily bypassed.
Para 3: the implication that removing all ghgs from the atmosphere would make the -18 deg C composite emitter in radiative equilibrium with Space coincide with the Earth's surface, hence the ghe is the difference between it and the present 15 deg C average, is plain wrong. No clouds or ice would increase SW energy by 43% so the real surface temperature would be 4 – 5 deg C, a ghe of ~ 11 K. The ratio 33/11 is the imaginary 'positive feedback'. That this passed 'Science's' peer review shows this failed then and has continued to fail for 32 years.
As for the real story, that involves irreversible thermodynamics and correction of Sagan's mistaken aerosol optical physics. The sign of the real effect of pollution on cloud albedo is reversed. In 2004, NASA claimed the fake 'surface reflection from small droplets argument' to get AR4. Now we have Trenberth claiming imaginary ocean heating to get AR5. There may be some, but it would be from the MWP!
It's time Hansenkoism is put in the dustbin marked 'Great Scientific Hoaxes of the Past'.

lemiere jacques

well.;regarding action that is supposed to be done to prevent warming it doesn’t change anything.
if you want to be SURE to prevent to be flooded , what is important is not how likely is a giant wave to be ‘(as its probability is not zero) but how hight a wave can be…and..that can be really very very veryvery expensive to avoid something very very very unlikely…

It seems to me that sensitivity in the high end of the usual range to 4 or 5 deg (or more) has typically been rare in the history of the modelling since the 1960s. A survey of 34 published sensitivity predictions published by William Clark in 1982 shows that half came in at 2 degrees or below. He comments on the the higher end results from 3D GCMs: ‘The NAS study in 1979 reviewed results available at that time concluded that the most likely (sensitivity) was 3 plus/- 1.5.’ But he notes that ‘the upper estimate relies heavily on…unpublished studies by Hansen’ & co at Goddard. He says no other GCM results exceed 3 deg. At this time Schneider and Revelle had just made the first big pitch to congress and with Hansen’s 1981 paper AGW broke through and grabbed the headlines. There is plenty of evidence of a scientists backlash against Hansen’s attention grabbing efforts in 1988, but here is Clark in 1982: ‘When atypical high estimates of sensitivity were proposed by GISS and reported by NAS, but the supporting data and calculations remain unavailable for independent review, there was little more than disgruntled mumblings. The implied double standard should be removed.’

Phillip Bratby

A few degrees of warming plus a lot of CO2 would do wonders for agriculture and the economy in general in the UK.


It appears from this report that the IPCC pseudo scientists and their paymasters are complete idiots. In the age of the Internet they are trying to engineer a “soft landing” using the old fashioned lame stream media technique of “slow walkback”, followed by “issue fade and replace”. This exit strategy just won’t work in the Internet age.
The basic question if very simple. Is the net effect of radiative gases in our atmosphere warming or cooling? The answer is that radiative gases act to cool our atmosphere at all concentrations above 0.0ppm. When they have gotten the science so totally and utterly wrong, no amount of “slow walkback” and no attempt at “issue fade and replace” is going to work. The shame of every person who sought to promote or profit by this inane hoax will burn on the Internet forever.

kadaka (KD Knoebel)

Dial back the sensitivity until the lower bound can yield the little bit of warming that did happen, but still keep an impossibly high upper bound. Claim the models do now match reality.
Then argue for immediate overwhelming action since when of course the higher temperatures will naturally happen that will then naturally average out the entire relevant temperature record to the long-term middle-range amounts predicted by the consensus of the world’s best climate science, well, it’ll be pretty bad.
Might as well use this temporary magical statistical hiatus for some good and get irrevocably committed to twice as many carbon emission reductions as we should have done ten years ago when the lucky pause started, right?

richard verney

In the recent article on the three options for the IPCC, I said that the IPCC cannot afford to ignore the recent paprs on lower climate sensitivity.
The fact is that the worth of the IPCC report will not be judged in 2013 when it is released to the usual fanfare and distorted press releases, but rather in 2015 when negotiations begin at the next climate conference.
If there is no warming between now and then there will be between 19 and 24 years without any warming. This is a distinct possibility and even the Met Office (who I have no confidence in) are suggesting that warming will not resume before 2017. Accordingly, one can expect to see more papers between now and 2015 discussing climate sensitivity and all these will be suggesting lower climate sensitivity to that expresses in AR4. AR5 would become an irrelevance if it was so out of kilter with developments showing up by 2015.
In my opinion, the revisions are more psychological than of substance. A sensitivity of 6 degC (with positive water feedback) is rediculous since in the paleo record there are many instances of high CO2 levels and cool temperatures as well as rising CO2 levels and cooling temperatures. These examples are inconsistent with high sensitivity at least if coupled to positive feedback and it is only positive feedback that permits even lip service to hifgh climate sensitivity since without positive feedback, climate sensitivity must inevitably be low. So dropping the obviously absurd claim as may be as high as 6degC merely drops an example where the IPCC claims are so obviously over exaggerated that little confidence can be had in their work as a whole.
Matters will, in 2015, be very contentious. Negotiators will inevitable look at the previous report (AR4) and compare it with AR5. As I understand the leak, there is no claim that climate sensitivity is ‘likely’ above 2degC. That is a game changing amendment since that was the battle ground and the rasion d’etre for the action.
We are now left with the position that it is ‘likely’ to be above 1.5degC and significantly even this is down from a probability of ‘very likely’ above 1.5degC.
All of this suggests (ie., the reading between the lines postion) is that we are looking at Climate Sensitivity somewhere between 1.5degC to 2degC, but not above that figure. That is according quite well with the recent papers on climate sensitivity.
Over the next few years, if the pause continues, I expect to see claims regarding climate sensitivity coming down. However, by 2015 there probably will not be a plethora of papers cl;aiming a sensitivity of below 1.5degC so there probably will be nothing to give the IPCC AR5 a fatal blow before the 2015 climate conference takes place.
It seems to me that the IPCC have judged matters quite cleverly to keep the gravy train alive and not to derail the 2015 climate conference. Perhaps given the speciality of the President, he knows something about derailing, and has in this particlular instance been politically astute.


I am not convinced they can measure the earths temp to that degree, not now not in the past not in the future.


IPCC Irresponsible Prophets of their Cargo Cult
They are finetuning their message of doom, so what. The IPCC should be trialed for the mess they have created worldwide: the billions lost in wind en solar, the billions lost in foodburning.


The art of diplomacy is to say nice doggy until you find a stick that is big enough. They are just trying to wait it out hoping for the next El Niño?

The AGW-scare was killed at the failed 2009 IPCC Conference in Copenhagen. I then wrote on WUWT and elsewhere

The AGW-scare is dead but it will continue to move as though alive in similar manner to a beheaded chicken running around a farmyard. It continues to provide the movements of life but it is already dead. And its deathly movements provide an especial problem.
Nobody will declare the AGW-scare dead: it will slowly fade away. This is similar to the ‘acid rain’ scare of the 1980s. Few remember that scare unless reminded of it but its effects still have effects; e.g. the Large Combustion Plant Directive (LCPD) exists. Importantly, the bureaucracy which the EU established to operate the LCPD still exists. And those bureaucrats justify their jobs by imposing ever more stringent, always more pointless, and extremely expensive emission limits which are causing enforced closure of UK power stations.
Bureaucracies are difficult to eradicate and impossible to nullify.
As the AGW-scare fades away those in ‘prime positions’ will attempt to establish rules and bureaucracies to impose those rules which provide immortality to their objectives. Guarding against those attempts now needs to be a serious activity.

I stand by everything I wrote in late 2009, and I consider the need to guard against “rules and bureaucracies” to be growing in importance.
The reduction to asserted climate sensitivity is part of the ‘fading away’ of the AGW-scare.
As the scare fades those who want the “rules and bureaucracies” can see they are running out of time to obtain their desires so they can be expected to increase their pressure to get what they want.

Jack Savage

It is an interesting thought experiment to imagine that this article had been written by, say, James Hansen, Al Gore or George Monbiot. Would the news be greeted with a huge sigh of relief from all the catastrophists, or would a great tide of hate roll in and cries of “denier” be heard?
Personally, the whole idea of there being a figure for the “sensitivity of climate” directly attributable to a trace gas, notwithstanding its properties, strains my credulity.
However, greater minds than mine seem convinced that this is the case and so I suppose I must accept it. However, you will have to continue to excuse my incredulity that anyone could yet come anywhere close to calculating it correctly.


The IPCC will gradually morph into something else over a number of years. Its remit will change into something which means nobody can claim it was disbanded. CO2 induced climatastrophe will be left to wither on the vine, hopefully to eventually drop out of view. This way, nobody has to admit fault and nobody loses their jobs.
The trick is to do this before any obvious harm comes from past policies aimed at averting CO2 catastrophe.
Expect lots of legislation to be repealed and targets quietly missed.
Expect lots of denial about who said what in the past, claims of having been misreported, and explanation of what they really meant, or passing the blame around in circles so nobody can be individually blamed.
It is unrealistic to expect any kind of “public execution” of the most active alarmists.
Unfortunately, this will also leave a residual of grass roots diehards who will bleat-on about CO2 climatastrophe for decades to come.

Peter Miller

By deduction AR7 and AR 8 – assuming this pseudo-science organisation is not tossed into the dustbin of bad science by then – will be predicting an imminent ice age.
That means they were right to move from ‘global warming’ to ‘climate change’ and we were wrong all along – sarc off.


AR5 – precis: what ifs and buts and not a lot else.
Now then, it seems to me – and way, way past it’s sell by date [by about 25 years] the end of the line has been reached.
And not before time, because personally I believe the mere fact that we’ve reached a fifth assessment was stretching the patience of mankind but particularly the western world to go on funding this ludicrous gravy train junket [UNEP IPCC].
At long last, it’s time to decommission this particular loco-train and shunt it into a siding, with its engine master – where he and it can rust and seize up in perpetuity – and in glorious silence.

Peter Miller:
Your post at September 14, 2013 at 2:40 am says in total

By deduction AR7 and AR 8 – assuming this pseudo-science organisation is not tossed into the dustbin of bad science by then – will be predicting an imminent ice age.
That means they were right to move from ‘global warming’ to ‘climate change’ and we were wrong all along – sarc off.

I suggest there is no need for your sarc tag.
Around the turn of the century – when alarmists were still proclaiming the then recent ENSO peak was a sign of things to come – I wrote the following in several places on the web.
“The global temperature fell from ~1940 to ~1970.
Alarmists then claimed emissions of SO2 from power generation were disrupting the climate system so were threatening climate disaster from global cooling.
The global temperature started to rise after ~1970.
By ~1980 it was no longer possible for alarmists to scare about global cooling so they morphed the scare into fear of global warming.
Alarmists then claimed emissions of CO2 from power generation were disrupting the climate system so were threatening climate disaster from global warming.
If global temperature were to cool for a decade then the global warming scare would probably be morphed back to global cooling scare.”
Alarmists always ridiculed this whenever and wherever I posted it.
We have not had a decade of clear global cooling, but global warming has ceased for a decade, and the global warming scare is being reigned-back.
One is often forgiven for being wrong but rarely forgiven for being right. (Sigh)


The fun part is as the IPCC backs down , the AGW fanatics will turn on them like rabid dogs , as they show time and again how badly the react to ‘anyone’ that dares to question the purity of ‘the cause ‘
Popcorn futures just went up as the left does want it does so very well , step itself in the back,.


So now perhaps the IPCC would care to explain the Minoan and Roman Optima, both of which were (if GISP2 data is to be believed) rather warmer than today, by about 2 degrees C…..
Thought not.


It looks like we’ll hit the 2C target without any action. 🙂

J Martin

There will surely be a statement for policy makers at the end where they will state that the need for anti co2 measures are more urgent than ever and that policy makers should seize the opportunity afforded them by the pause to build windmills and destroy the economy. Also implying that governments keep funding the gravy train.
I feel that if they make no mention of the possibility that cooling is possible, then they will have painted themselves into a corner with no available exit strategy. The writing is on the wall, after 23 years of no significant warming and the last 8 years showing a slight cooling trend, there is every chance that we could see a steeper cooling trend arrive, PDO, AMO, Livingston and Penn (ap ?).


“very likely be less than 6C” – clearly for the benefit of those that preach the “precautionary principle”.

RC Saumarez

For the US, what will the EPA’s response be to lower climate sensitivity?

Jean Parisot

>> The AGW-scare was killed at the failed 2009 IPCC Conference in Copenhagen.
I believe the fatal wound was the 97-0 no confidence vote Al Gore received upon his return from Kyoto in a Democrat controlled Senate. Without the US economy bleeding into the carbon markets, the whole charade didn’t make sense.

Those models are really starting to take quite a beating from reality


By not stating a “most likely” number, they are consciously obscuring the fact that climate sensitivity has been climbing down.
They also refuse to describe 4-6 degrees as f. ex “unlikely”, even though this would be a natural thing to do according to how they deal with the lowest numbers.
Here we see IPCCs bias in reporting the science quite clearly. Always maintaining the threat, never admitting to any positive scientific developments.
It is politics in its purest sense.

William Astley

The IPCC is making progress. It will be interesting to listen to the explanation for cooling.


All this despite empirical evidence that it is temperature that drives CO2 not the reverse as assumed by the IPCC.

The IPCC will morph into global cooling concernism, it will suggest then a policy for a world government to enforce a mandate to increase release of ghg into the atmosphere to mitigate cooling.
When asked why the models of the previous 20 years did not predict climate cooling then the IPCC will say the cheapskate US government never provided enough funds for modeling to achieve accuracy.

Jean Parisot:
At September 14, 2013 at 3:23 am you quote my having said

The AGW-scare was killed at the failed 2009 IPCC Conference in Copenhagen.
and add

I believe the fatal wound was the 97-0 no confidence vote Al Gore received upon his return from Kyoto in a Democrat controlled Senate. Without the US economy bleeding into the carbon markets, the whole charade didn’t make sense.

You make an interesting point and you may well be right, but historians will debate such matters for years to come.
I observe that if you are right then the importance of that vote was not recognised (although many – including me – trumpeted it).
The Kyoto Protocol restricted a ‘basket’ of six GHGs (notably CO2) by Annex A (i.e. developed) countries. Annex B (i.e. developing countries) were exempted from the restrictions. This encouraged Annex B countries to support the Protocol because the constraints on Annex A countries encouraged transfer of industrial activity from Annex A countries to Annex B countries.
Indeed, this encouragement of transfer of economic activity is why e.g. the USA refused to ratify the Kyoto Protocol.
The 2009 Copenhagen Summit was intended to provide a successor to the Kyoto Protocol. It was hoped this successor would encompass all major GHG emitting emitting countries. Simply, it would – in effect – move e.g. China from Annex B to Annex A.
Developed countries proclaimed this proposed new Protocol as being a way to “Save The World”. The then British Prime Minister declared the Copenhagen Summit was “Six days to save the world!”. And the newly elected US President attended the Summit (the US government said) in fanfare for the same reason .
In reality, the government leaders 2009 attended the Copenhagen Summit for economic reasons.
The proposed new Protocol would inhibit industrial development in developing nations and, thus, inhibit the increasing economic competitiveness of the developing nations.
China was an Annex B country and the proposed new Protocol would – in effect – make China an Annex A country. So, China would have none of it, and the negotiations to obtain a successor to the Kyoto Protocol failed.
That failure is not reversible. And, therefore, the main political motivation for the AGW-scare was killed at the 2009 Copenhagen Summit.

Frans Franken

lemiere jacques says:
September 14, 2013 at 1:15 am
I expect the same. There will likely be much appeal to the timely installed precautionary principle. The probability of dangerous warming may be smaller (reduced climate sensitivity), but the consequences of it will be stressed as disastrous. Risk = Probability x Consequence. Alarmist governments will persevere in very expensive mitigation measures to try and avoid this risk. The amount of warming c.q. climate sensitivity will not much interest politicians, until they understand that it’s very very very probable that it will remain below their self-defined danger threshold of 2 C.

I apologise for the formatting errors in my above post.

Bill Illis

I admit I am surprised by this development and sure hope it comes to turns out to be the case.
Other than the 6.0C outlier, the numbers quoted in the article are much closer to what appears to be the reality. Didn’t think we would see this happen at this time.


Bill Illis says:
September 14, 2013 at 4:22 am
Other than the 6.0C outlier, the numbers quoted in the article are much closer to what appears to be the reality. Didn’t think we would see this happen at this time.
I think they have no choice but to give up the warming aspect of CAGW. Instead they are concentrating all their political force on “extreme” events. Of course there is no increase in extreme events, but an increase in reporting said events can keep the funding going, and can be used as an excuse by political hacks like Obama to attack the coal industry. The C the G and the W are MIA from CAGW.

Dodgy Geezer

…Most experts believe that warming of less than 2 degrees Celsius from preindustrial levels will result in no net economic and ecological damage. Therefore, the new report is effectively saying (based on the middle of the range of the IPCC’s emissions scenarios) that there is a better than 50-50 chance that by 2083, the benefits of climate change will still outweigh the harm….
So there is a gap in the market place for ‘expert’ opinion that warning of LESS than 2 deg could be dangerous?
Look for a new generation of ‘climate experts’ to fill that gap over the next few years….

Dodgy Geezer

…I apologise for the formatting errors in my above post….
“It is a good rule in life never to apologise. The right sort of people do not want apologies, and the wrong sort take a mean advantage of them.”
― P.G. Wodehouse, The Man Upstairs and Other Stories


And so the climb down begins…… Has there ever been a finer quango than the IPCC?. I would have preferred my tax dollars went to those that truly needed them but then I suppose all bets are off around the dog bowl at feeding time.

Bill Illis:
Your post at September 14, 2013 at 4:22 am says

I admit I am surprised by this development and sure hope it comes to turns out to be the case.
Other than the 6.0C outlier, the numbers quoted in the article are much closer to what appears to be the reality. Didn’t think we would see this happen at this time.

Well, I am not “surprised” and I suspect many others are not, too.
The ‘pause’ makes a reduction of climate sensitivity necessary if the scare is to be kept staggering on. When asked,
“Why does the pause exist?”
they can answer with words to the effect,
“We slightly overestimated climate sensitivity, but as the science has progressed so we have corrected that in the light of new knowledge. We are 95% certain that AGW is real and we need to prevent the horrors it threatens.”
It is hard to see an alternative tactic which would keep the scare going in the light of the ‘pause’.
Please note the careful nature of the new statement.
A climate sensitivity is “likely” to be above 1.5°C and “very likely” to be below 6°C. Thus, they can claim to be making a conservative assessment because they refute the most extremist – and ridiculous – alarmist claims but keep the scare alive.
Also, importantly, they do not withdraw (because they do not mention) their assertion in the AR4 that the “most likely” value is a scary 3°C. If they were being honest then THAT is the value they would have most considered.


Don’t be confused by the 1980s and 1990s warming. Much of that was natural (ENSO) but some was from Asian aerosols reducing cloud albedo, a process that saturated in about 2000.
The reason is that Sagan’s aerosol optical physics is wrong – he missed out a second optical process. The result of this is that the sign of the effect is reversed. There was no significant CO2 warming.