You may remember headlines like these last summer:
A new paper by a team of NOAA scientists published in the Bulletin of the American Meteorological Society finds that the US extreme heat wave of March 2012 was due to natural variability, not AGW. According to the authors, “Several lines of evidence strongly implicate natural variations as the primary cause for the extreme event,” and “We conclude that the extreme warmth over the central and eastern U.S. in March 2012 resulted primarily from natural climate and weather variability, a substantial fraction of which was predictable.”
They go on to show how synoptic scale weather forecasting models like GFS predicted the event, indicating it was a “weather, not climate” event. Now that the analysis says ‘natural variability”, will there be followup headlines? Doubtful. News of “normalcy” doesn’t sell, hype and sensationalism does. However, I’m going to take this opportunity to call out Climate Central’s Andrew Freedman, who is one of the more reasonable people who sensationalized the event, to post a follow up to his collection of stories on it here.
The full paper is below.
Randall Dole 1, Martin Hoerling 1, Arun Kumar 2, Jon Eischeid 1,3, Judith Perlwitz 1,3, Xiao-Wei Quan 1,3,George Kiladis 1, Robert Webb 1, Donald Murray 1,3, Mingyue Chen 2, Klaus Wolter 1,3, and Tao Zhang 1,3
1 NOAA Earth System Research Laboratory, Boulder, Colorado 2 NOAA Climate Prediction Center, Camp Springs, MD 3 University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, Colorado
We examine how physical factors spanning climate and weather contributed to record warmth over the central and eastern U.S. in March 2012, when daily temperature anomalies at many locations exceeded 20°C. Over this region, approximately 1° C warming in March temperatures has occurred since 1901. This long-term regional warming is an order-of-magnitude [10 times] smaller than temperature anomalies observed during the event, indicating the most of the extreme warmth must be explained by other factors. Several lines of evidence strongly implicate natural variations as the primary cause for the extreme event.
The 2012 temperature anomalies had a close analogue in an exceptionally warm U.S. March occurring over 100 years earlier, providing observational evidence that an extreme event similar to March 2012 could be produced through natural variability alone. Coupled model forecasts and simulations forced by observed sea surface temperatures (SSTs) show that forcing from anomalous SSTs increased the probability of extreme warm temperatures in March 2012 above that anticipated from the long-term warming trend.
In addition, forcing associated with a strong Madden-Julian Oscillation further increased the probability for extreme U.S. warmth and provided important additional predictive information on the timing and spatial pattern of temperature anomalies. The results indicate that the superposition of a strong natural variation similar to March 1910 on long-term warming of the magnitude observed would be sufficient to account for the record warm March 2012 U.S. temperatures.
We conclude that the extreme warmth over the central and eastern U.S. in March 2012 resulted primarily from natural climate and weather variability, a substantial fraction of which was predictable.
Full paper (draft revision submitted) is available here:
h/t to The Hockey Schtick