Reactions to Otto et al
May 20, 2013
Bishop Hill in Climate: sensitivity

Press reactions to the Otto et al paper vary from the sublime to the ridiculous.

Matt Ridley in the Times (£) points to the policy implications and notes that mitigation now looks like a pretty daft approach to take:

It is true that the “transient climate response” is not the end of the story and that the gradual warming of the oceans means that there would be more warming in the pipeline even if we stopped increasing carbon dioxide levels after doubling them. But given the advance of nuclear and solar technology, there is now a good chance we will have decarbonised the economy before any net harm has been done.

Fiona Harvey in the Guardian, meanwhile, is trying to push TCR of 1.8°C as "human disaster looming". This is so absurd as to almost defy belief. At the rate of warming implied by the paper, the impacts of global warming are more likely to be positive than negative for the foreseeable future.

Staying with the ridiculous, New Scientist argues that the prospect of little warming for decades to come should add impetus to efforts to secure a global climate deal.

And the paper's lead author is also keen to spin the results, the FT reporting his remarks as follows: the long term, temperatures are still likely to rise to potentially dangerous levels of more than 2°C above those of pre-industrial times, unless greenhouse gas emissions are curbed. that means there is no reason to believe sceptics’ claims that the earth has stopped warming or that climate policies are a waste of money, said the report’s lead author, Alexander Otto of Oxford university’s Environmental Change Institute.

I'm not sure whether Dr Otto has quite grasped the concept of discounting. I think he might have been better sticking to the science than getting involved with the economics.

The BBC also reckons the results do not mean much:

...when it comes to the longer term picture, the authors say their work is consistent with previous estimates. The IPCC said that climate sensitivity was in the range of 2.0-4.5C. 

This latest research, including the decade of stalled temperature rises, produces a range of 0.9-5.0C.

"It is a bigger range of uncertainty," said Dr Otto.

"But it still includes the old range. We would all like climate sensitivity to be lower but it isn't."

Perceptive readers will note that the range quoted of 0.9-5deg;C is different to that quoted by Nic Lewis in his article here last night. The difference is that the BBC is using the whole data range (which includes the poor quality data from the 1970s) whereas Nic is quoting the figure derived only from the most recent and therefore better quality, data. I think reasonable people can differ here, but it is important to note that the mode of the estimate produced by the full range is lower than that of the single-decade estimate.

Update on May 20, 2013 by Registered CommenterBishop Hill

James Annan reckons the authors are spinning the results:

The results are described in rather strange terms, considering what they have actually presented. They argue that the new result for sensitivity "is in agreement with earlier estimates, within the limits of uncertainty". But of course none of the published estimates are inconsistent with each other in the sense of having non-overlapping uncertainty ranges - no-one credible has excluded a value of about 2.5C, that I am aware of. The contrasting claim that the analysis of transient response gives a qualitatively different outcome (being somewhat lower than both the previous IPCC assessment, and the range obtained from GCMs) is just weird, since both their ECS and TCR results are markedly lower than the IPCC and GCM ranges.

This looks like a pretty unreasonable attempt to spin the result as nothing new for sensitivity, when it is clearly something very new indeed from these authors, and implies a marked lowering of the IPCC "likely" range.

Update on May 20, 2013 by Registered CommenterBishop Hill

Actually the quote re the consistency between AR4 and the new paper is not as credible as I thought. The AR4 estimate of 2-4.5°C range is for 17-83%. The range quoted in the BBC article is 5-95%. Apples to oranges. Apparently the justification is that IPCC practice is to down-grade uncertainties by at least one level to account for structural uncertainties. Not sure I find this convincing.

Update on May 20, 2013 by Registered CommenterBishop Hill

Annan has written a second post on the Otto et al paper, which I think is going to stir things up nicely.

Article originally appeared on (
See website for complete article licensing information.