Climate sensitivity is a perennial topic here, so the multiple new papers and discussions around the issue, each with different perspectives, are worth discussing. Since this can be a complicated topic, I’ll focus in this post on the credible work being published. There’ll be a second part from Karen Shell, and in a follow-on post I’ll comment on some of the recent games being played in and around the Wall Street Journal op-ed pages.
Technical Note: Sorry for any recent performance issues. We are working on it.
Amid the manufactured spin and excitement of the unofficial release of the IPCC WG1 Second Order Draft, it is worth remembering that this happened last time too:
IPCC draft: No comment
May 4, 2006
As everyone has now realised, the second-order draft of the new IPCC report has become very widely available and many of the contributors to this site, commenters and readers will have seen copies. Part of the strength of the IPCC process are the multiple stages of review – the report is already significantly improved (in clarity and scientific basis) from the first round of reviews, and one can anticipate further improvements from the ongoing round as well. Thus no statements from this draft report can be considered ‘official’. While most of the contents of the report will come as no surprise to frequent visitors here, we have decided that we are not going to discuss the report until it is finalised and released (sometime in February 2007). At that time, we’ll go chapter by chapter hopefully pulling out the interesting bits, but until then, we feel it’s more appropriate to respect the ‘Do not cite or quote’ injunctions that can be found on every page. We trust that our commenters will likewise respect the process. Patience, people, patience!
The only change is that AR5 will be released in September 2013.
One might assume that people would be happy that the latest version of the Hadley Centre and CRU combined temperature index is now being updated on a monthly basis. The improvements over the previous version in terms of coverage and error estimates is substantial. One might think that these advances – albeit incremental – would at least get mentioned in a story that used the new data set. Of course, one would not be taking into account the monumental capacity for some journalists and the outlets they work for to make up stories whenever it suits them. But all of the kerfuffle over the Mail story and the endless discussions over short and long term temperature trends hides what people are actually arguing about – what is likely to happen in the future, rather than what has happened in the past.
The fundamental point I will try and make here is that, given a noisy temperature record, many different statements can be true at the same time, but very few of them are informative about future trends. Thus vehemence of arguments about the past trends is in large part an unacknowledged proxy argument about the future.
Guest commentary from Barry Bickmore (repost)
The Wall Street Journal posted yet another op-ed by 16 scientists and engineers, which even include a few climate scientists(!!!). Here is the editor’s note to explain the context.
Editor’s Note: The authors of the following letter, listed below, are also the signatories of“No Need to Panic About Global Warming,” an op-ed that appeared in the Journal on January 27. This letter responds to criticisms of the op-ed made by Kevin Trenberth and 37 others in a letter published Feb. 1, and by Robert Byer of the American Physical Society in a letter published Feb. 6.
A relative sent me the article, asking for my thoughts on it. Here’s what I said in response.
Back in 2007, the IPCC AR4 SPM stated that:
“Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”
This is a clear statement that I think is very well supported and correctly reflects the opinion of most climate scientists on the subject (and was re-affirmed in two recent papers (Jones and Stott, 2011;, Huber and Knutti, 2011)). It isn’t an isolated conclusion from a single study, but comes from an assessment of the changing patterns of surface and tropospheric warming, stratospheric cooling, ocean heat content changes, land-ocean contrasts, etc. that collectively demonstrate that there are detectable changes occurring which we can attempt to attribute to one or more physical causes.
Yet, in a paper just out in BAMS (Curry and Webster, 2011) this statement is apparently evidence that IPCC is unable to deal with uncertainty. Furthermore, Judith Curry has reiterated on her blog that the term ‘most’ is imprecise and undefined. For instance:
Apart from the undefined meaning of “most” in AR4 (which was subsequently clarified by the IPCC), the range 50.1-95% is rather imprecise in the context of attribution.
However, Curry’s argument is far from convincing, nor is it well formed (why is there a cap at 95%?). Nor was it convincing when I discussed the issue with her in the comments at Collide-a-Scape last year where she made similar points. Since the C&W paper basically repeats that argument (as has also been noticed by Gabi Hegerl et al who have a comment on the paper (Hegerl et al.)), it is perhaps worth addressing these specific issues again.
- G.S. Jones, and P.A. Stott, "Sensitivity of the attribution of near surface temperature warming to the choice of observational dataset", Geophysical Research Letters, vol. 38, pp. n/a-n/a, 2011. http://dx.doi.org/10.1029/2011GL049324
- M. Huber, and R. Knutti, "Anthropogenic and natural warming inferred from changes in Earth’s energy balance", Nature Geosci, vol. 5, pp. 31-36, 2011. http://dx.doi.org/10.1038/ngeo1327
- J.A. Curry, and P.J. Webster, "Climate Science and the Uncertainty Monster", Bulletin of the American Meteorological Society, vol. 92, pp. 1667-1682, 2011. http://dx.doi.org/10.1175/2011BAMS3139.1
- G. Hegerl, P. Stott, S. Solomon, and F. Zwiers, "Comment on “Climate Science and the Uncertainty Monster” J. A. Curry and P. J. Webster", Bulletin of the American Meteorological Society, vol. 92, pp. 1683-1685, 2011. http://dx.doi.org/10.1175/BAMS-D-11-00191.1