New global water vapor findings contradict second draft of IPCC Assessment Report 5 (AR5)
Guest post by Forrest M. Mims III
I was an “expert reviewer” for the first and second order drafts of the 2013 Intergovernmental Report on Climate Change (IPCC) Assessment Report 5 (AR5). The names and reviews of all the reviewers will be posted online when the final report is released. Meanwhile, reviewers are required to not publish the draft report. However, the entire second draft report was leaked on December 13, 2012, without IPCC permission and has subsequently received wide publicity.
My review mainly concerns the role of water vapor, a key component of global climate models. A special concern is that a new paper on a major global water vapor study (NVAP-M) needs to be cited in the final draft of AR5.
This study shows no up or down trend in global water vapor, a finding of major significance that differs with studies cited in AR5. Climate modelers assume that water vapor, the principle greenhouse gas, will increase with carbon dioxide, but the NVAP-M study shows this has not occurred. Carbon dioxide has continued to increase, but global water vapor has not. Today (December 14, 2012) I asked a prominent climate scientist if I should release my review early in view of the release of the entire second draft report.
He suggested that I do so, and links to the official IPCC spreadsheet version and a Word version of my review are now posted near the top of my homepage at www.forrestmims.org.
A PDF version (prepared by Anthony from the Word version) is here: Mims_IPCC_AR5_SOD_Review
A relevant passage from the AR5 review by Mimms (added by Anthony):
The obvious concern to this reviewer, who has measured total column water vapor for 22.5 years, is the absence of any mention of the 2012 NVAP-M paper. This paper concludes,
“Therefore, at this time, we can neither prove nor disprove a robust trend in the global water vapor data.”
Non-specialist readers must be made aware of this finding and that it is at odds with some earlier papers. Many cited papers in AR5 have yet to be published, but the first NVAP-M paper was published earlier this year (after the FOD reviews) and is definitely worthy of citation: Thomas H. Vonder Haar, Janice L. Bytheway and John M. Forsythe. Weather and climate analyses using improved global water vapor observations. GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L15802, 6 PP., 2012. doi:10.1029/2012GL052094.