More from the empty set

Readers may remember the fun we had with a couple of papers at the start of the year. Cai et al found that climate models that simulated extreme rainfall well predicted more frequent El Ninos. Meanwhile Sherwood et al found that climate models that simulated clouds well had high climate sensitivity, a position that I characterised as "the best cloud simulators are the worst temperature simulators". Much amusement ensued when it emerged that the intersection of "best cloud simulators" with "best rainfall simulators" was in fact the empty set.

Leo Hickman now points us to a new paper by Su et al, which examines some climate models and concludes:

New model performance metrics proposed in this work, which emphasize how models reproduce satellite observed spatial variations of zonal-mean cloud fraction and relative humidity associated with the Hadley Circulation, indicate that the models closer to the satellite observations tend to have equilibrium climate sensitivity higher than the multi-model-mean.

This is an admirable confirmation of Sherwood's findings. Like I said: the best cloud simulators are the worst temperature simulators.

A debate!

The Institute of Art and Ideas recently held a debate which was a bit of a shocker in that it included people who are less than convinced that we are about to fry. Bob Carter needs little introduction of course, but alongside him were atmospheric physicist Michael McIntyre and science writer and climatologist Richard Corfield, none of whom would fall into the eco-catastrophe camp. The debate was chaired by Gabrielle Walker, familiar to readers here as co-author of David King's dodgy book on climate. This is really very good stuff. (The embedding doesn't seem to work for me - direct link here).

On consistency

In the wake of the Press Gazette "debate", I was watching an exchange of views on Twitter between BH reader Foxgoose and Andrea Sella, a University College London chemist who moves in scientific establishment and official skeptic circles.

Sella was explaining how persuasive he found the observational record of climate:

Think like a scientist! Temperature is only a proxy. Energy balance is real issue & C19 physics is alive and well.

Like Warren Buffett you mustn’t be affected by shorter term fluctuations.

As I said, don’t just look at surface temps. Look at sea level and global ice mass too. All part of same.

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Causes for the pause

David Whitehouse has a new GWPF note out, examining all the different post-hoc explanations for the hiatus in global warming. To introduce it, there's a short film which can be seen here.

Some comments on the Royal Society report

Reader Alex Henney sends some comments on The Royal Society/National Academy of Sciences Report on Climate Change that he sent to the President of the Royal Society and the British authors of the report.¹

It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are, if it doesn’t agree with experiment, it’s wrong.

Richard Feynman

1. The document continues to espouse models which are flawed, see p. 5, even though the final draft of the 2013 SPM commented “Models do not generally reproduce the observed reduction in surface warming trend over the last 10-15 years”.  John Christy² compared the performance of 39 climate model that were used in AR5 over the period 1975 to 2012 with measured temperature data.  The models over back-cast temperature significantly in a range 0-0.7^oC. 

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Walport's presentation

Mark Walport's staff have kindly made available the slides he used in Glasgow. They can be seen here.

As I have suggested previously, the talk was a recitation of the standard case for alarm, but there were many aspects of it that piqued my interest. For example, I noted that while warming up to the first slide he spoke about energy security first, before moving on to climate. Later on in the talk he spoke of the three lenses through which the climate problem had to be viewed and the first of these was again energy security. Is this a new tack? Are backsides starting to be covered? Perhaps.

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Something a bit neffy

The New Economics Foundation are well known for their outlandish policy prescriptions and for their extreme reluctance to use economics to support them. This is all entertaining stuff but they have now decided to dip their feet into the climate change waters, with a new paper that purports to show that climate scientists are much better at predicting the future than economists.

They may well be right, but I was struck by some of the evidence they have used to support this view. They have taken some of the IPCC's predictions, apparently from the Second Assessment Report, and have tracked them against subsequent observations. Take the temperature one for example:

It's instructive to take a look at this post at Watts Up With That?, which looks at the predictions of each of the IPCC assessments and notes that SAR makes the coolest prediction of temperature increase and still came out too warm by quite a long way.

I'm not sure that nef picking the IPCC's best performing prediction and holding it up as representative is what you might call a credible assessment of climatologists' abilities.

Lewis on Shindell

Updated on Mar 10, 2014 by Bishop Hill

Nic Lewis has a post up at Climate Audit, looking at the new paper by Gavin Schmidt's colleague Drew Shindell.

Shindell, the lone author of the paper, looks at CMIP5 models and claims to show that there are distinct differences between the climate's sensitivity to different forcings. Once these are taken into account, and once a lot of adjustments are made to them too, it is possible to show (allegedly) that low climate sensitivity to carbon dioxide is not possible.

These adjustments are not trivial, as Lewis explains:

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Climatese whispers

A new comment piece in Science by Clement and DiNezio (£) reviewing support for the idea that Trenberth's famous "missing heat" is lurking in the depths of the Pacific Ocean. This is a fairly unobjectionable paper, delivered in a moderate tone, with only the inevitable profession of the faith at the paper's close - "Greenhouse gases are warming the planet, and will continue to do so" - distracting from the main thrust.

The support for the idea that the Pacific is key seems to come chiefly from climate model studies, for example the "mind-blowing" Kosaka and Xie study and a paper by Meehl. Observational evidence seems rather harder to come by:

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Santer: pause now 20 years long

David Whitehouse has taken a look at the Santer et al paper in Nature Geoscience that claims to find a partial explanation for the hiatus in surface temperature rises in the cumulative effect of a series of small volcanic eruptions.

As an aside, Whitehouse notes that once you have adjusted the temperature data for the non-AGW effects, the pause in warming is very long indeed:

Their Fig 1 shows raw lower temperature data (a), that with the El Nino removed (b) and that with El Nino and El Chichon and Pinatubo removed (c). Looking at 1c one sees that the lower atmosphere shows a standstill since 1993, that is 20 years! This is in itself a remarkable graph extending the ‘pause’ into the start of its third decade.

And suffice it to say, the attribution to volcanoes is shonky indeed.

Parliamentary feedback

The Parliamentary Office of Science and Technology (POST) has come to the attention of this blog from time to time, most notably when it was noticed that it was chaired by Lord Oxburgh and included a member of the Russell panel. Lord O has now stood down as chairman and has been replaced by Adam Afriyie MP, but remains on the board.

POST has just issued a briefing on climate feedbacks and this is interesting reading. It was written by a POST staffer, but the research was done by a secondee called Danny Heptinstall, who seems to be an ecology PhD student at the Aberdeen Centre for Environmental Sustainability (and whose secondment is being paid for by the British Ecological Society). Hmm.

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What to do with a hot model

One of the things I've noticed about climatologists is that once they get each generation of models out into the open they spend the following few years producing papers that analyse some aspect of the model output. This is no doubt an easy way of making an impact on the research evaluation exercises to which all academics are subjected. And if the papers are accompanied by bloodcurdling headlines about future disaster are no doubt good for promotion, salary increases and invitations to speak to the United Nations.

This paper (via Leo Hickman's Twitter feed) looks to be from the same drawer. Here's the abstract:

Trends of Arctic September sea ice area (SSIA) are investigated through analysis of Coupled Model Intercomparison Project phase 5 (CMIP5) data. The large range across models is reduced by weighting them according to how they match nine observed parameters. Calibration of this refined SSIA projection to observations of different 5 year averages suggests that nearly ice-free conditions, where ice area is less than 1 × 10⁶ km², will likely occur between 2039 and 2045, not accounting for internal variability. When adding internal variability, we demonstrate that ice-free conditions could occur as early as 2032. The 2013 rebound in ice extent has little effect on these projections. We also identify that our refined projection displays a change in the variability of SSIA, indicating a possible change in regime.

So far so bloodcurdling. However, it seems to me that the authors, and indeed the climatological community as a whole, have a problem. We know that the aerosol forcing figures in the CMIP5 models are far greater than the best observational evidence would suggest. This being the case the models will necessarily run too hot. This presumably makes the claim that the Arctic ice will be gone by 2032 just a weeny bit shaky.

Aren't they going to have to sort the aerosols out before they can start to make predictions?

Update on Feb 2, 2014 by Bishop Hill

And here's another!

The empty set

Readers will recall my posts on two recent papers which looked at how climate models simulated various aspects of the climate system, using these to draw inferences about our future. The Sherwood et al paper picked the models that best simulated clouds and showed that these predicted that the future would be hot. "Planet likely to warm by 4C by 2100", wailed the Guardian. Meanwhile, the Cai et al paper picked the models that best simulated extreme rainfall and showed that these predicted more frequent extreme El Nino events. "Unchecked global warming 'will double extreme El Niño weather events'", the Guardian lamented.

Reader Patagon wondered, not unreasonably, which models fell at the intersection of "best climate model simulation of clouds" and "best climate model simulation of extreme rainfall", and his question prompted the following response from Nic Lewis:

I was also wondering that. So I've cross-referred between the new Cai et al. ENSO/extreme rainfall paper, and the recent Sherwood et al. paper tracing the spread in climate sensitivity to atmospheric convective mixing and implying therefrom that climate sensitivity is over 3°C.

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From the least absurd models

A few days ago, I mentioned a paper that had looked at climate model simulation of clouds and found that the ones that did the best job of this narrow task produced the highest predictions of temperature rises. As I noted at the time this means that one can paraphrase the findings as "best cloud simulators are worst temperature predictors" but, as is normal in these circumstances, the headlines were all about global warming being "worse than we thought".

Yesterday Nature published a similar paper, this time looking at the El Nino phenomenon. It seems that if you take the models that best simulate extreme rainfall they predict that extreme Ninos will take place much more frequently in future, with all the floods and droughts and the like that accompany them.

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Falsifiability in my lifetime

An article on the Nature website looks at the failure of global temperatures to rise in line with the climate models and finds a possible explanation in the Pacific Decadal Oscillation. I notice what may be the start of a new meme emerging:

...none of the climate simulations carried out for the IPCC produced this particular hiatus at this particular time. That has led sceptics — and some scientists — to the controversial conclusion that the models might be overestimating the effect of greenhouse gases, and that future warming might not be as strong as is feared. Others say that this conclusion goes against the long-term temperature trends, as well as palaeoclimate data that are used to extend the temperature record far into the past. And many researchers caution against evaluating models on the basis of a relatively short-term blip in the climate. “If you are interested in global climate change, your main focus ought to be on timescales of 50 to 100 years,” says Susan Solomon, a climate scientist at the Massachusetts Institute of Technology in Cambridge.

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