At the end of this month, the UN’s Intergovernmental Panel on Climate Change (IPCC) is scheduled to release the physical science basis of it Fifth Assessment Report on climate change. Between now and then, the final wording of its highly visible and influential Summary for Policymakers (SPM) will be hashed out in a meeting in Stockholm. The current draft version of the SPM has been “leaked” in order to drum up some media attention for the upcoming meeting/report.
Among many interesting statements in the draft SPM, this one particularly caught our eye:
[Climate] Models do not generally reproduce the observed reduction in surface warming trend over the last 10–15 years. There is medium confidence that this difference between models and observations is to a substantial degree caused by unpredictable climate variability, with possible contributions from inadequacies in the solar, volcanic, and aerosol forcings used by the models and, in some models, from too strong a response to increasing greenhouse-gas forcing. [italics in original, bold added by us]
We found this interesting because back in 2010, we, along with several co-authors, wrote a paper titled “Assessing the consistency between short-term global temperature trends in observations and climate model projections.” In that paper, we demonstrated that climate models do not generally reproduce the observed reduction in surface warming trend over the last 10-15 years. We also wrote that this was the result of some combination of inadequacies in the evolution of anthropogenic forcing (including aerosols), natural variability (both that which is captured and that which is insufficiently handled by climate models), as well as the strong possibility that climate models were producing too much warming for a given amount of greenhouse gas emissions.
Specifically, we wrote: