This morning, IPCC Working Group I (WGI) released its highly anticipated AR5 Summary for Policymakers on the physical science basis of climate change. The final paragraph of the report considers geoengineering:
Methods that aim to deliberately alter the climate system to counter climate change, termed geoengineering, have been proposed. Limited evidence precludes a comprehensive quantitative assessment of both Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR) and their impact on the climate system. CDR methods have biogeochemical and technological limitations to their potential on a global scale. There is insufficient knowledge to quantify how much CO2 emissions could be partially offset by CDR on a century timescale. Modelling indicates that SRM methods, if realizable, have the potential to substantially offset a global temperature rise, but they would also modify the global water cycle, and would not reduce ocean acidification. If SRM were terminated for any reason, there is high confidence that global surface temperatures would rise very rapidly to values consistent with the greenhouse gas forcing. CDR and SRM methods carry side effects and long-term consequences on a global scale. (p. 21)
This is a relatively balanced statement, justifiably skeptical but neither implacably opposed nor enthusiastically supportive. Language favorably disposed toward geoengineering, which the Guardian newspaper claimed was being pushed by the Russian delegation in a story last week (see Russia Pushing IPCC WGI to Recognize Geoengineering as Policy Option?, 9/20), is nowhere to be found. (The Guardian report did, however, provide vocal geoengineering critic Clive Hamilton the opportunity to draw an intimate connection between climate engineering and the predatory Russian state in a follow-on essay.) The IPCC will take up geoengineering at greater length when Working Group III (WGIII) on mitigation finalizes its contributions to AR5 next April in Berlin.
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