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I work for the British Antarctic Survey as a climate modeller; see my bio there. The views expressed here are in a personal capacity, as usual. I also have a rather confused wikipedia user page...
Lack of Errors in the IPCC Statement for Policymakers
20 Mar, 2007 10:47 am
The 2007 IPCC Statement for Policymakers (SPM) was released in early Febuary to extensive scrutiny, which it has survived well. Few skeptics have even attempted to engage with the science it describes; here I discuss one substantive, but failed, attempt to find errors in the SPM
1. The IPCC says that "snow cover have declined on average in both hemispheres".
Pielke asserts that it is "cherry picking" because snow cover was less in the late 1980's. But this is cherry picking on Pielke's part; analogous to the assertions made by some skeptics that "global warming stopped in 1998" because global temperature hasn't increased since that year.
2. "Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80% of the heat added to the climate system." This is probably the closest hit that Pielke makes, though the SPM statement is (of course) true. And in the context of the next sentence "Such warming causes seawater to expand, contributing to sea level rise" it makes good sense - what matters is the global average; hence complaining that this occured largely in the southern ocean is beside the point. Pielke's point that a 2006 paper finds recent cooling may well be true (though one paper is not definitive) but 2006 papers were beyond the IPCC cut-off date, as Pielke knew very well.
3. Pielke asserts that the IPCC's "The average atmospheric water vapour content has increased since at least the 1980s over land and ocean as well as in the upper troposphere. The increase is broadly consistent with the extra water vapour that warmer air can hold" conflicts with the observation of no significant change in global mean precipitation. There is no conflict: substantial changes in atmospheric water vapour (Q) can amount to no more that a fraction of one days precipitation (P): the change in Q is observable; the change in P would be below the noise level.
4. This is perhaps the strangest of the lot. Pielke objects to the statement "Mid-latitude westerly winds have strengthened in both hemispheres since the 1960s" although he sources it to his own paper on the grounds that it is inconsistent with Arctic tropospheric warming, a subject that the SPM does not even mention. This therefore cannot be an inconsistency in the SPM; and nor can it be an error, unless Pielke believes his own paper to be wrong. As Gavin Schmidt pointed out to Pielke somewhat earlier, the SPM is probably talking about the surface winds not the upper atmosphere winds anyway, in which case the point evaporates.
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Regarding #1, snow cover has not decreased in recent years. To exclude this information in the IPCC SPM is cherrypicking at best and deliberate misrepresentation otherwise.
On #2, where the heat is inserted in a global study IS important. This heat can be more easily sequestered deep in the ocean. The 2003-2005 ocean heat loss was known before the cut-off date of the IPCC SPM.
For #3, evaporation must equal precipitation when averaged over long time periods. This is basic mass conservation. The atmosphere cannot continue to accumulate water!
On #4, the results of our paper are misrepresented. We found NO hemispheric increase or decrease in westerlies over the last part of the 20th century. We did find zonally averaged regions of increase and decrease.
Finally, William did not comment on my weblog
"The Net Climate Feedbacks Must Be A Negative Effect On The Global Average Radiative Imbalance If The IPCC Conclusion Of Net Anthropogenic Radiative Forcings Is Correct"
http://climatesci.colorado.edu/2007/03/19/climate-feedbacks-must-be-a-negative-effect-on-the-global-average-radiative-imbalance-if-the-ipcc-conclusion-of-anthropogenic-radiative-forcings-are-correct/
We would benefit by your comments on yet another major issue with the IPCC SPM.
Point #4... well, my source was you. If anyone has misrepresented your paper, its yourself. As I've pointed out, Gavin pointed out to you that the SPM was talking about surface winds anyway, so your entire point becomes irrelevant.
I apologise for not commenting on everything you write; but you've had 4 shots at finding errors, all of which fail; it doesn't encourage me to look further. This "discussion" with you appears to be stuck, in that you insist on seeing errors where no-one else can.
"The carbon dioxide radiative forcing increased by 20% from 1995 to 2005, the largest change for any decade in at least the last 200 years. {2.3, 6.4}"
I calculate (roughly, based on figure 2.4 of the draft IPCC WG1 Fourth Assessment Report) that the increase in radiative forcing from 1970 to 1980 was from 0.84 to 1.06 W/m^2, which is 26%. So the SPM statement appears to be incorrect that the largest % change was 1995 to 2005.
Of course this is due to % change in forcing from 1750 being a likely poor way of characterization. 1865 to 1875 appears to show a 34% change using this method!
That is probably why they said "... in at least the last 200 years."
Calculating ' as a % of the value in 2005.' is not what they said they did and would be a very non-standard way of calculating % increase when talking about previous decades.
It is time for a complete new look at climate change, by independent auditors. Current workers in the field are too often tied into entrenched interests, such as Al Gore and carbon trading schemes.