A new NOAA Climate Program Office-sponsored study on extreme 
temperatures has been published in the prestigious academic journal Nature. The article describes how changes in the frequency of certain atmospheric circulation patterns are linked to observed changes in the frequency of regional temperature extremes during recent decades. The article was authored by Dr. Daniel Horton (Stanford University), Dr. Nathaniel Johnson (University of Hawaii, Princeton University) – whose contribution was funded by the Climate Program Office’s Modeling, Analysis, Predictions, and Projections (MAPP) Program – and several other scientists from Stanford University. In the study, the researchers tested the hypothesis that observed trends toward more frequent extreme warm or cold conditions over regions of the Northern Hemisphere over the past few decades can be linked to increases or decreases in the frequency of certain atmospheric patterns. They used a state-of-the-art technique, self-organizing map cluster analysis, to search for trends in circulation patterns during both the satellite observation era of 1979–2013 and the recent period of rapid Arctic sea-ice decline during 1990–2013.
The journal article can be found here: http://www.nature.com/nature/