date: Fri Sep 18 16:02:25 2009 from: Phil Jones subject: Re: comments on Thompson et al. Nature paper to: Thomas C Peterson Tom, I recall talking about this paper to Mike at the last CCPP meeting in DC. It should be easier to explain the revised record, but it may mean that sulphate aerosols become less important. Skeptics will use anything to undermine things. The change when corrections are applied (which should be submitted soon) will make the 1940s warmer overall, so will affect the key AR4 diagram from D&A - well the specific ocean one. This paper has just been accepted - attached. You can also get another at Congratulations! Your recently accepted article, "Low-frequency variations in surface atmospheric humidity, temperature and precipitation: Inferences from reanalyses and monthly gridded observational datasets", is now available on the AGU Papers in Press site: [1]http://www.agu.org/journals/jd/papersinpress.shtml#id2009JD012442 Another one with Dave Thompson is on the J. Climate accepted page as well. I wish I could find some time to write papers as first author!!! Cheers Phil At 14:01 18/09/2009, you wrote: Hi, Phil, Dick Reynolds and I passed on a copy of the Thompson, Kennedy, Wallace and Jones paper on the large discontinuity...to Mike MacCracken. I thought you might enjoy his comments, the key one being: The only disappointment about the article from my view are its limited comment on the implicationsI think they will be huge. Regards, Tom ************************* Hi Tom and DickThank you very much for sending along the paper, I had not yet seen it though understood the UK efforts were looking at this period. I was interested in how the US contribution to the measurements grew starting in something like 1939 (when Lend-Lease started) and grew more gradually than when it shut downso it is indeed the whole period that will be affected. The only disappointment about the article from my view are its limited comment on the implicationsI think they will be huge. It is this (uncorrected) warmth that has been the basis for so much of the interest in solar contributions to climate change, so that will be seriously impacted, getting us back to where many of us think we should be, with solar changes in heating being weighted about equally with GHG changes in heating and not having to search out all sorts of exotic feedbacks to show how a small solar change could have a disproportionately large effect. So, I think it will mean the detection-attribution studies weigh solar less and find the human influence going back further in time. Many of the Skeptics have also using that early 1940s level to be the end of natural warming post the Little Ice Age, saying human influences played little early role (though methane concentration was up a lot, and CO2 some, so there was actually a significant forcing prior to the early 1940s, but its influence was misestimated as there was this focus on the Sun (how it can be so constant is truly amazing, but that is what it appears). I think there was also an important and unfortunate psychological result of the 1940s high pointnamely it hid the early human influences and so let the argument be made that natural variability (internal and external) was larger than it has been, so the problem was not as bad as it really is. I have for quite a number of years asked people to put their finger over the WWII period and then look at the global record, and one gets a quite different impression of hat has been happening and its relation to human activities, etc. Basically, now, it will seem much more evident that human activities started earlier. I think the new result will also affect the estimate of the aerosol offsetthe only way to be explaining the mid-20th century was with a pretty large sulfate cooling. Now, that wont be nearly so necessary, likely making that aerosol effect smaller, which will be interesting. It will therefore also affect the ideas about geoengineering with sulfate aerosols. And finally, the result may help in figuring out why estimates of sea level rise during the 20th century have been so far below observationsIPCCdrawing from the model results--could only explain a small share of 20th century rise. Less sulfate and solar influence and more even warming over time might well help in this regard. So, again, fascinatingit will be nice now to have a citation for a situation that I have been pointing out in talks and my 2008 review paper. Best, Mike Prof. Phil Jones Climatic Research Unit Telephone +44 (0) 1603 592090 School of Environmental Sciences Fax +44 (0) 1603 507784 University of East Anglia Norwich Email p.jones@uea.ac.uk NR4 7TJ UK ----------------------------------------------------------------------------