U.S. Deep Freeze, December 2016

There has been speculation that record low temperatures would be coming to the United States this week, and this has been framed as either evidence against global warming in general or that cold air outbreaks are increasing due to climate change. WWA presents a quantitative study of the current cold air outbreak. WWA researchers compute how rare the outbreak is and how it is affected by human-caused greenhouse gases. The analysis uses the same methods as WWA used in the peer-reviewed analysis of the cold extremes in the Midwest in the winter of 2013 – 2014 (van Oldenborgh et al, 2015).