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The mind-boggling coincidence hypothesis

Also hot off the press is a new paper by Gavin Schmidt and colleagues. Doug McNeall reckons I'm not going to like it, but having taken a look (it's open access for registered users of the Nature website), I have to say I think it's lots of fun.

Schmidt and his colleagues are looking at the hiatus in surface temperature rises and considers why the CMIP5 ensemble all got it so wrong. In their new paper they explain that the reason for this is not – as wild-eyed readers at BH might think – that the models are wonky. In fact it's all down to an incredible, incredible coincidence

Here we argue that a combination of factors, by coincidence, conspired to dampen warming trends in the real world after about 1992. CMIP5 model simulations were based on historical estimates of external influences on the climate only to 2000 or 2005, and used scenarios (Representative Concentration Pathways, or RCPs) thereafter4. Any recent improvements in these estimates or updates to the present day were not taken into account in these simulations. Specifically, the influence of volcanic eruptions, aerosols in the atmosphere and solar activity all took unexpected turns over the 2000s. The climate model simulations, effectively, were run with the assumption that conditions were broadly going to continue along established trajectories.

Apparently, if you go back and rework all the forcings, taking into account new data estimates (add half a bottle of post-hoc figures) and 'reanalyses' of old data (add a tablespoon of computer simulation) you can bridge the gap and explain away the pause.

We conclude that use of the latest information on external influences on the climate system and adjusting for internal variability associated with ENSO can almost completely reconcile the trends in global mean surface temperature in CMIP5 models and observations. Nevertheless, attributing climate trends over relatively short periods, such as 10 to 15 years, will always be problematic, and it is inherently unsatisfying to find model–data agreement only with the benefit of hindsight.

So, with the benefit of hindsight, the climate modellers can fit their square peg into a round hole. It wasn't that the models were running too hot, it was just that nature has got it in for climate modellers.


Of course, they still have the problem that the energy budget estimates of TCR are all pointing to much lower climate sensitivity than the GCMs. These studies are, of course, strongly suggestive of the "mind-boggling coincidence" hypothesis being incorrect and the original supposition - that the models are overheated - is right. However, Schmidt and his colleagues make no attempt to address such minutiae, waving them aside, with characteristic bonhomie, as mere speculation:

We see no indication, however, that transient climate response is systematically overestimated in the CMIP5 climate models as has been speculated8, or that decadal variability across the ensemble of models is systematically underestimated, although at least some individual models probably fall short in this respect.

Told you it was fun, didn't I?

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Reader Comments (182)

The dog ate my homework

Feb 27, 2014 at 4:56 PM | Unregistered CommenterSpen

Climate "science", astrology, numerology, water diving, tea leaf reading, etc. what is the difference?

They all get well paid for writing any old crap.

Feb 27, 2014 at 5:03 PM | Unregistered CommenterCharmingQuark

In internet parlance, this article efforts can be categorized as "Doubling down on the derp"

Feb 27, 2014 at 5:05 PM | Unregistered CommenterWalt Stone

Specifically, the influence of volcanic eruptions, aerosols in the atmosphere and solar activity all took unexpected turns over the 2000s.

Could somebody point me to the paper(s) by a vulcanologist that details either the increase in volcanic eruptions since 2000 or the sudden change in the constituents of a volcanoes output?

The only place I've heard about a this is in climate related papers.

Feb 27, 2014 at 5:05 PM | Unregistered CommenterTerryS

The dog ate my homework volcanoes.

I suppose all the adjustments which make the past look colder were also coincidence:

Gavin Wins The 2014 World Cup Of Data Tampering In Brazil

(Blue=GISS v2, Red = GISS v3)

Feb 27, 2014 at 5:07 PM | Registered Commenterlapogus

They call themselves scientists? This new scientific method based on coincidence was not covered in my degree course.

Using method A, the speed of light is measured to be 2x10^8m/s. Using method B, the speed of light is measured to be 4x10^8m/s. By coincidence, the speed of light is actually 3x10^8m/s.

Feb 27, 2014 at 5:18 PM | Registered CommenterPhillip Bratby

'conspired ' only in their own minds

Meanwhile climate 'science' continues to show its professionals cannot work at the standards normally expected for an undergraduate handing in an essay.

Feb 27, 2014 at 5:25 PM | Unregistered Commenterknr

I don't yet have access to the full paper, but it is unclear to me whether this "coincidence" has finished yet. If not, how long do they expect the coincidence to continue?

Feb 27, 2014 at 5:30 PM | Unregistered Commentermichael hart

Reminds me of this scene from The Blues Brothers:

Jake: No, I didn't. Honest... I ran out of gas. I... I had a flat tire. I didn't have enough money for cab fare. My tux didn't come back from the cleaners. An old friend came in from out of town. Someone stole my car. There was an earthquake. A terrible flood. Locusts! IT WASN'T MY FAULT, I SWEAR TO GOD!

Feb 27, 2014 at 5:32 PM | Unregistered CommenterNW

"inherently unsatisfying"

Just like Real Climate, then.

Feb 27, 2014 at 5:40 PM | Registered Commenterjamesp

"Conspiring factors of errors in volcanic and solar inputs, representations of aerosols, and El Niño evolution, may explain most of the discrepancy."

It's a conspiracy theory - call Lewandowsky!

Feb 27, 2014 at 5:40 PM | Registered CommenterPaul Matthews

So if this coincidence means that they "can almost completely reconcile the trends in global mean surface temperature in CMIP5 models and observations", is Gavin concluding that the deep ocean heat theory is rubbish?

Feb 27, 2014 at 5:41 PM | Unregistered CommenterAndyL

As any good carpenter knows, if you want a square peg fit in a round hole, use a very big hammer.

Feb 27, 2014 at 5:42 PM | Unregistered CommenterAndrew


The science is settled.


For now.

Feb 27, 2014 at 5:45 PM | Unregistered CommenterStuck-Record

Gavin and Doug - the 'coincidence' idea has been discussed many times by David Whitehouse who has a different take from you. You see coincidence as a rare line up of factors to cancel out warming. Dr Whitehouse asked the question what is it telling us. IS IT a coincidence that all the various known and presumably unknown cooling factors EXACTLY balance out the positive forcings YEAR ON YEAR with the cooling keeping perfect pace with the warming. You say that's a coincidence but in the pages of the GWPFDr Whitehouse says it's indicative of something else, a clue about the response of the climate. You see coincidence as a desperate appeal to a one in a thousand chance stacked up to thwart your theories. There are other, more scientific, ways to see it. A pause is a paradigm hiding in plain sight.

Feb 27, 2014 at 5:48 PM | Unregistered CommenterCbebe

As 10cc sang "You've got to be joking Mann"

Feb 27, 2014 at 5:57 PM | Unregistered Commenterdbd

So we are to expect "CCC" (Catastrophic Climate Coincidences) to become the new buzz phrase are we?

Feb 27, 2014 at 5:59 PM | Unregistered CommenterIvor Ward

I noticed they say their models have been wrong since 1992 ("conspired to dampen warming trends in the real world after about 1992"). Does that mean the "pause" as they define it has been ongoing for 22 years? Is the 15 years stuff only coming after 1998?

Feb 27, 2014 at 6:04 PM | Unregistered CommenterRickA

Schmidt. What a hack.
Susan Solomon hss been touting the idea that tiddly non straospheric eruptions have somehow caused the cooling. Utter tripe.

Feb 27, 2014 at 6:12 PM | Unregistered CommenterTallbloke

As I asked Tasmin I will ask Gavin:

Do the models explain why rate of warming between 1910 – 1940 is about the same as the rate of warming between 1975 and 2004?

Feb 27, 2014 at 6:13 PM | Unregistered CommenterIbrahim

From Wikipedia, re "Adding epicycles"
In part, due to misunderstandings about how deferent/epicycle models worked, "adding epicycles" has come to be used as a derogatory comment in modern scientific discussion. The term might be used, for example, to describe continuing to try to adjust a theory to make its predictions match the facts.

So, we know what they are doing.

Feb 27, 2014 at 6:24 PM | Unregistered CommenterBengt Abelsson


So, do the new, super-improved, science-is-settled models, hind-cast 1910-1940's warming?
And how long do they predict the predicted/non-predicted 'pause' to go on for?
And has Gavin told Mann he thinks there is a pause? Michael still claims there hasn't been. That must have been an awkward conversation.

Feb 27, 2014 at 6:27 PM | Unregistered CommenterStuck-Record

Ibrahim, you probably know the answer to your Q, but if not take a look at IPCC AR5 WG1 figure 9.8.
The models in the top fig are too warm in 1910, and those in the lower fig are too cool in 1940.

Feb 27, 2014 at 6:34 PM | Registered CommenterPaul Matthews

The science is correct. Unfortunately, as Nature says, nature is behaving incorrectly,

Feb 27, 2014 at 7:27 PM | Unregistered CommenterRoy

"unexpected turns"

They must be kidding. Climate change is linear.

"The climate model simulations, effectively, were run with the assumption that conditions were broadly going to continue along established trajectories."

They drew a graph and using a magic marker continued the temperature line from 1980 to 1998!

They never noticed the pause from 1944 to 1980? Or that the line from 1909 to 1944 never kept going up?


Feb 27, 2014 at 7:27 PM | Unregistered CommenterBruce

Paul Matthews,

It would be a great if they'd explain the influence of the different forcings, don't you think?

Feb 27, 2014 at 7:29 PM | Unregistered CommenterIbrahim

Add this paper to a long list of similar ones, created to provide "scientific" cover for an inconvenient truth. The average punter or politician won't look behind the resulting headlines that the pause is explained and global warming continues.

The 97% consensus figure comes from the same stable.

Feb 27, 2014 at 7:40 PM | Registered Commenterwoodentop

The epicycle analogy is an insult to the Ptolemaic astronomers. Their models actually predicted the movement of the planets reasonably well.

Feb 27, 2014 at 7:51 PM | Unregistered CommenterBloke in Central Illinois

They have no shame!

Feb 27, 2014 at 8:04 PM | Unregistered CommenterEd Caryl

Science does not proceed by superficial - and often highly prejudiced - discussions on internet blogs. If you have any meaningful criticisms of the paper mentioned above I suggest you do what every climate scientist is required to do: publish a formal, technical argument in a major journal.

If you can't do that, you don't have anything meaningful to say.

Feb 27, 2014 at 8:11 PM | Unregistered CommenterNoel Darlow

This is looking more and more like a test of faith. Who will be the first to crack?

Feb 27, 2014 at 8:20 PM | Unregistered CommenterAnything is possible

Noel, don't be daft. This is the internet you are on. There may be real criticisms of the paper but those who are not subject to the rules of scientific discussion are still allowed to voice them without all the rigmarole of papers, comments, corrections and retractions which are a hangover from a past age. There have been papers quite recently which have been retracted or relegated to limbo based on internet, even blog, objections.

Feb 27, 2014 at 8:31 PM | Unregistered Commenterrhoda

Noel, see here for one example of how access to journals works in climate "science":

Feb 27, 2014 at 8:40 PM | Registered Commenterwoodentop

Don't mess with Noel Darlow, Rhoda - he's the guy who gives lectures on climate science to Ryan Maue.

Feb 27, 2014 at 8:43 PM | Registered CommenterFoxgoose

Quaking in my plimsolls.

Feb 27, 2014 at 8:46 PM | Unregistered Commenterrhoda

..or perhaps sandshoes would be more appropriate.

Feb 27, 2014 at 8:48 PM | Unregistered Commenterrhoda

We need only presume that this article is a parody, and then it all makes sense.

A quotation in the Wikipedia article on "Parody" --

In his 1960 anthology of parody from the 14th through 20th centuries, critic Dwight Macdonald offered the general definition, "Parody is making a new wine that tastes like the old but has a slightly lethal effect."

Feb 27, 2014 at 8:48 PM | Registered CommenterSkiphil

We have reached the point where they are basically saying "Pay no attention to that man behind the curtain."

Feb 27, 2014 at 8:53 PM | Unregistered CommenterBloke in Central Illinois

Wont wash here, sorry.

The climategate emails laid bare the whole pal review and carefully guarded journal scam.

The best way to win that game is not to play.

Feb 27, 2014 at 8:53 PM | Unregistered CommenterNW


The Soon / De Freitas debacle shows a perfectly proper defence of academic standards after the publication of some manifestly bad science from Soon et al which would almost certainly have been rejected if it had been properly peer reviewed.

Do we seriously still have to deal with all those facile "climategate" allegations, a decade later..?

Feb 27, 2014 at 9:02 PM | Unregistered CommenterNoel Darlow

Most importantly, our analysis implies that significant warming trends are likely to resume, because the dominant long-term warming effect of well-mixed greenhouse gases continues to rise. Asian pollution levels are likely to stabilize and perhaps decrease, although lower solar activity may persist and volcanic eruptions are unpredictable. ENSO will eventually move back into a positive phase and the simultaneous coincidence of multiple cooling effects will cease. Further warming is very likely to be the result.

Simultaneous coincidence of multiple cooling effects..........Utter Bollocks

Sorry Bish, needed to be said.


Maybe this is the reason that hindcasts are always more accurate than forecasts, the forcings are always adjusted retrospectively and this just proves that forecast forcings are pure guesswork.

Feb 27, 2014 at 9:06 PM | Unregistered CommenterLord Beaverbrook

"......And evil paper eating moths were chewing on my homework, which was accidentally written in invisible ink, before the dog snatched it off the table, and ran into the rain where the boogeyman who hates my homework grabbed it, and then a mighty wind broke out from heaven and knocked over the boogeyman, and spread the papers around and all I could bring in was this wad of paper. So can I get another week to finish?"

"And if you don't believe me, you are practicing motivated reasoning and are denying the brilliance of my work and are being paid by that bully who never liked me."

There, there, all better Gavin.

Feb 27, 2014 at 9:12 PM | Unregistered Commenterhunter

Climate "science", astrology, numerology, water diving, tea leaf reading,

That's about the lot so we need a new one. None of these amply describes this paper. Are they serious? Or seriously stupid.

Feb 27, 2014 at 9:12 PM | Unregistered CommenterStephen Richards

Don't mess with Noel Darlow, Rhoda - he's the guy who gives lectures on climate science to Ryan Maue.

Feb 27, 2014 at 8:43 PM | Registered CommenterFoxgoose

Oooh, That dick heade

Feb 27, 2014 at 9:15 PM | Unregistered CommenterStephen Richards

Science does not proceed by superficial - and often highly prejudiced - discussions on internet blogs.

So how does it progress? In shadey offices with cucumber sandwiches on the table and a bunch of mates. Oh, got it in one.

Feb 27, 2014 at 9:17 PM | Unregistered CommenterStephen Richards

Do we seriously still have to deal with all those facile "climategate" allegations, a decade later..?
Feb 27, 2014 at 9:02 PM Noel Darlow

Well I don't know about "facile allegations" but I downloaded the file from the Russian server and the emails seemed pretty damning to me. A lot of things fell into place.

Feb 27, 2014 at 9:17 PM | Registered CommenterMartin A

Gavin & gang are acting like UFO promoters who predicted ET would land and are trying to explain away their failure.
Of course we get to comment, point out, laugh, guffaw and ridicule.
He and his pals have hustled the world for billions and all they have to show for it is transparent arm waving to explain away their utter failure.
We need a real audit- *all* the records, correspondence, inter-locking boards and commissions and committees, green mail, phony NGO's, etc.
A few tens of billions here, a few tens of billions there, and it all adds up to a lot of money after awhile.
And you have *nothing* to show for it. No new tech to help the environment, no way to actually even store CO2, no low cost energy, no accuarate weather forecasts, nothing. Zip. NAda. AGW hypesters have wasted our time.
And you clowns are responsible for an increasingly nasty cult that threatens people for merely disagreeing over some trivial point of science.
So grow a pair, back off and start acting like a responsible adult and not some cult-addled mindless twit.

Feb 27, 2014 at 9:25 PM | Unregistered Commenterhunter

Excellent post, Bish. Schmidt and his fun loving friends are not going to be bound by scientific method. When the observations disagree with the models, the problem is caused by coincidences that can be uncovered only in hindsight. They deserve credit for dreaming up a new rationale for the old trick of introducing "ad hoc" hypotheses to explain away failures.

Karl Popper's work went beyond his account of falsification. He wrote quite a lot about 'ad hoc' hypotheses and presented many examples of their use to save falsified hypotheses. Schmidt and his friends should study Popper. In addition, they should exercise some common sense. Science is never in the rear view mirror.

Feb 27, 2014 at 9:28 PM | Unregistered CommenterTheo Goodwin

If you had a six-sided dice and you threw two 1's in a row, you wouldn't attempt to claim that the average score of a six-sided dice is 1, not 3.5. I'd like to think you would continue the experiment until you had a sample large enough to draw some meaningful conclusions.

The same error is made when people talk about the "pause" as a significant climate event. Even if we hadn't detected any global warming, a period of fifteen years is far too short to say anything meaningful about climate. We know there is a large amount of year-to-year and decade-to-decade variability. The climate trend is a long-term average which by definition is not affected by short-term variability - just like the average dice score of 3.5 is not affect by a run of 1's, or 6's, etc.

Attttribution of the pause is an interesting problem but not one which has any bearing on the long-term climate trend.

The only reason it is talked about at all is because it gives false skeptics some ammunition to make unscientific claims. Model runs frequently throw up periods of faster than average or slower than average cooling although of course they can't predict the precise timing of every random climate event. The pause just isn't that interesting unless you have an axe to grind.

Feb 27, 2014 at 9:35 PM | Unregistered CommenterNoel Darlow

Stephan Lewandowsky usually studies conspiratorial ideation closely. Best wait to hear what he has to say on the matter before jumping to conclusions cartoons.

Feb 27, 2014 at 9:40 PM | Unregistered CommenterAnonymous

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