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« Recollections of Bob Carter | Main | Probable cause - Josh 358 »
Monday
Jan252016

A "substantial" error in GISS Model E

Over the weekend Nic Lewis posted a brief update to his latest posting on the Marvel et al paper. In it, he described something he had unearthed in a paper by Chandler et al. I've reproduced it here.

I have just discovered (from Chandler et al 2013) that there was an error in the ocean model in the version of GISS-E2-R used to run the CMIP5 simulations. The single forcing simulations were part of the CMIP5 design, although it is possible that some or all of them were run after the correction was implemented.

Chandler et al write:

We discuss two versions of the Pliocene and Preindustrial simulations because one set of simulations includes a post-CMIP5 correction to the model’s Gent-McWilliams ocean mixing scheme that has a substantial impact on the results – and offers a substantial improvement, correcting some serious problems with the GISS ModelE2-R ocean.

explaining the problem as follows:

...the simulations described here as “GM-CORR” utilise a correction to the Gent- McWilliams parameterisation in the ocean component of the coupled climate model. In prior implementations of the mesoscale mixing parameterisation in GISS ModelE, which like many ocean models uses a unified Redi/GM scheme (Redi, 1982; Gent and McWilliams, 1990; Gent et al., 1995; Visbeck et al., 1997), a miscalculation in the isopycnal slopes led to spurious heat fluxes across the neutral surfaces, resulting in an ocean interior generally too warm, but with southern high latitudes that were too cold. A correction to resolve the problem was made for this study, and it will also be employed in all subsequent versions of ModelE2-R going forward.

Interestingly, they also write:

One of the most significant differences of the Pliocene GM CORR simulations, compared with those of the uncorrected model, is the characteristic of the meridional overturning in the Atlantic Ocean. In GM UNCOR the Atlantic Meridional Overturning Circulation (AMOC) collapsed and did not recover, something that was expected to be related to problems with the ocean mixing scheme. Although we hesitate to state that this is a clear improvement (little direct evidence from observations), it seems likely that the collapsed AMOC in the previous simulation was erroneous.

It occurs to me to wonder whether this error in the GISS-E2-R ocean mixing parameterisation may account for its behaviour in Land use change run 1. It looks like something goes seriously wrong with the AMOC in the middle of the 20th century in that run, with no subsequent recovery evident. I have been unable to ascertain as yet whether that simulation was run using the uncorrected or the corrected ocean module code.

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Reader Comments (22)

It's interesting to speculate about whether GISS's contribution to the IPCC reports are affected by this error.

Jan 25, 2016 at 8:34 AM | Registered CommenterBishop Hill

Can I just say my brain hurts after reading this?

Jan 25, 2016 at 9:36 AM | Unregistered CommenterCharlie Flindt

More coffee, Charlie, more coffee.

Jan 25, 2016 at 9:49 AM | Registered CommenterBishop Hill

All we need to do is wait for a few days, observe the hand-waving and be told that this error "doesn't matter" - conclusions are "robust", even if there is no explanation to say why.

Jan 25, 2016 at 10:13 AM | Unregistered CommenterDerek

I think you need an image of a train wreck.

Jan 25, 2016 at 10:13 AM | Unregistered CommenterIt doesn't add up...

Charlie Flindt
I avoid headaches by concentrating only on the stuff I understand. An error in a climate model was discovered in 2013, but the information was only circulated widely in 2016. Nothing unusual so far.
What makes it interesting is that in the meantime the whole world decided to spend trillions over decades trying to do useless things that can't be done, on the basis of knowledge of the future based on those same models. That's what makes my head hurt.

Jan 25, 2016 at 10:17 AM | Registered Commentergeoffchambers

Is this where The Day After Tomorrow alarms keep coming from? They're using the model, rather than the actual measurements?

Jan 25, 2016 at 10:29 AM | Unregistered CommenterTinyCO2

Having seen more of Gavin Shcmidt's public outpourings than I suspect is entirely healthy - Derek's description of a GISS response is missing one component - the swaggering sneer.

I also suspect haruspices were equally dismissive of the rabble.

Jan 25, 2016 at 10:33 AM | Registered Commentertomo

Rather than 'correct' the paper, isn't it normal practice in climate science (and a lot cheaper) to adjust the numbers they started with, so the conclusion is still correct?

Jan 25, 2016 at 11:55 AM | Unregistered Commentergolf charlie

News evaluation: "Something wrong in climate models" equals "Dog bites postman".
I´m waiting for the news: "Something right with climate models".

Jan 25, 2016 at 11:59 AM | Unregistered CommenterBengt Abelsson

Having seen Gavin Schmidt's TED talk I came away thinking that the man is in love with his modeling. (For what its worth, I am not a big fan of TED talks as all limitations and issues seem to be brushed aside to present a rosy, limitless opportunities from the technology at hand. We are scientists after all and the problems are what we work and often, the opportunities lie nested in those problems.) With such a strong vested interest in the outcome of the models, it would surprise no one to think that the data must be made to conform to the construct. This probably delights administrators and bureaucrats while scaring good scientists.

Jan 25, 2016 at 12:07 PM | Unregistered CommenterSean

A scientoid looks like a scientist, writes like a scientist, talks like a scientist. He is indistinguishable from a scientist, save for the fact that he is bogus.

Jan 25, 2016 at 1:07 PM | Unregistered Commenterdearieme

In climate 'science' it is only an error if you get the result you don't want , otherwise its fine . Honesty and accuracy are not part of what make something good or bad in this area.

Jan 25, 2016 at 2:04 PM | Unregistered Commenterknr

The old "miscalculation in the isopycnal slopes ". Catches me every time.


Pardon my ignorance, but isn't this a conflict between one guess and another, and not to be taken seriously?

Jan 25, 2016 at 2:35 PM | Unregistered Commenterrhoda

rhoda, it is not the quality of the guesswork, but the quantity of the press coverage that earns the best money.

Jan 25, 2016 at 3:03 PM | Unregistered Commentergolf charlie

Errors in CMIP5 models are nothing new.
http://judithcurry.com/2013/06/28/open-thread-weekend-23/#comment-338257

Jan 25, 2016 at 5:19 PM | Unregistered CommenterCurious George

The various CMIPs have reported errors online over the years. Some CMIP5 problems are summarized here: http://cmip-pcmdi.llnl.gov/cmip5/errata/cmip5errata.html

It always amuses me when Climate Scientists endless publicly denounce, in very derogatory ways, errors in other’s work for years afterward, but always fail to mention the problems that have been identified in all the CMIPs over the years.

Curious George,
You might be interested in these additional errors:
http://bishophill.squarespace.com/discussion/post/1915791

Jan 25, 2016 at 7:31 PM | Registered CommenterPatagon

It's the same way climate alarmist tried to convince everyone that 2 degrees is really 10 degrees and their wife that 3 inches is really seven inches.

Jan 25, 2016 at 8:20 PM | Unregistered CommenterJamspid

"I think you need an image of a train wreck." --It doesn't add up...

That is a train, shewn to climatological accuracy. More precisely, it resembles a train to the approximate degree that a climate model represents the Earth's climate.

Jan 25, 2016 at 10:38 PM | Unregistered Commenterjorgekafkazar

Even simple programs get extensive updates and corrections that are described in explicit detail as to exactly what the problem was and what the fix should accomplish.

Then this ever science misbehaving group of clods writes in this little correction note:

"...a miscalculation in the isopycnal slopes led to spurious heat fluxes across the neutral surfaces, resulting in an ocean interior generally too warm, but with southern high latitudes that were too cold. A correction to resolve the problem was made for this study..."

Offhand, from what they loosely claim their correction fixes, does not include fixes to land use change runs or modules.

"...t looks like something goes seriously wrong with the AMOC in the middle of the 20th century in that run, with no subsequent recovery evident. I have been unable to ascertain as yet whether that simulation was run using the uncorrected or the corrected ocean module code..."

Does it matter? Seriously wrong is seriously wrong.

Jan 26, 2016 at 4:19 AM | Unregistered CommenterATheoK

"That is a train, shewn to climatological accuracy."

Damn you man: I snorted tea.

Jan 26, 2016 at 4:50 AM | Unregistered CommenterClunking Fist

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