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Roger Pielke Jr.'s avatar

FYI, my Dad will have a post shortly on ocean heat content as a better metric of global warming than atmospheric temperatures ... stay tuned

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Sean Rush's avatar

I became an Expert Reviewer for AR6 wg1 partly because of this issue. I had written a paper for my Masters (in climate science and policy) referring to Christy and McNider’s paper “Satellite Bulk Tropospheric Temperatures as a Metric for Climate Sensitivity” Asia-Pac. J. Atmos. Sci., 53(4), 1-8, 2017, DOI:10.1007/s13143-017-0070-z” which showed the lack of warming in the upper troposphere – the ‘missing hotspot.’ Dr Christy had alerted me to observational charts published by the IPCC in AR5 as ‘supplemental’ material, months after the publication of the main report and the had story moved on (see figure 10.SM.1 from Chapter 10SM). These charts show a divergence between observations and modelled upper tropospheric warming. But the IPCC’s conclusion was that the models were probably correct and the problem lay with the satellites. Greenhouse warming should be most obvious in areas of the atmosphere with low water vapour – the upper troposphere and the North and South poles. Only the North pole shows conclusive evidence of warming.

My paper started as a simple energy budget review so I looked at the surface temperature record – specifically as covered by AR5 p.189. I went through the papers cited and was concerned to find they were not properly summarised. For example, Zhang et al 2010 found nearly a third of observed warming across China was attributable to UHI. But the IPCC only reported the study “found no evidence for urban influences in the desert North West region of China despite rapid urbanization.” This secondary finding was due to artificial oases, an explanation not included by the IPCC. I contacted Dr Ren, a co-author who had submitted expert comments in the Second Order Draft advocating for Zhang et al’s primary finding (which was stated as 'accepted'). Dr Ren considered that the language used was likely part of a predetermined decision on the issue.

I also looked at the comments to Chapter two, SOD, page 189 and saw there was considerable debate about what should be included and a divergence of views – 10 pages worth. Dr Phil Jones of the CRU, the lead author for AR4, contributes vociferously. Dr Ren submits as well as the likes of Christy and others arguing for higher levels of uncertainty.

The following comment was from Marcel Crok, The Netherlands, was accepted: “You should mention Fall, S., D. Niyogi, A. Gluhovsky, R. A. Pielke Sr., E. Kalnay, and G. Rochon, 2009: Impacts of land use land cover on temperature trends over the continental United States: Assessment using the North American Regional Reanalysis. Int. J. Climatol., 10.1002/joc.1996. [Fall et al 2010] This paper shows that most of the trends in the US can be explained by land use changes. In their words: "As most of the warming trends that we identify can be explained on the basis of LULC changes, we suggest that in addition to considering the greenhouse gases-driven radiative forcings, multi-decadal and longer climate models simulations must further include LULC changes."

This study was duly cited (top right of page 189) but the key conclusion, that LULC can account for most warming trends, was not reproduced – rather the conclusion was modified to simply say their Reanalyses work matched observations. Roger’s Dad was a co-author, with Eugenia Kalnay, Jule Charney’s protégé and a legend in the numerical weather prediction space. Kalnay and Cai 2004 had made a similar finding. But the IPCC’s conclusion was that the surface record was likely within 10% of that observed (‘high agreement’).

Needless to say I received a poor mark, the lowest in class, and a ‘sit down and talking to’ by two IPCC scientists on the faculty.

I was pleased to advocate for the inclusion of John Cristy’s conclusions in AR6 and to see that the IPCC modified their approach to now acknowledging, with medium confidence, that the upper troposphere observations are inconsistent to those modelled. They refused to address the shortcomings of their treatment of Fall et al 2010, saying it was out of scope for AR6.

Its good to see multiple study groups now agreeing with John, Roy and others. Hats off to their perseverance.

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