Tuesday, September 23, 2014

New paper finds low-CO2 US drought in 1934 was the most extreme of past Millennium

A paper published today in Geophysical Research Letters finds the Western North America dust bowl drought of the low-CO2 year 1934 was the most extreme drought by far of the past Millennium. In addition, the low-CO2 1934 heat, drought and extreme weather was a global phenomenon, not limited to the US. 

How did the most extreme drought by far over the past Millennium and global heat, drought, and extreme weather happen when the man-made CO2 'control knob' was out of commission? Could it possibly be that natural forces/forcing dominates the climate and man-made CO2 is not the 'control knob' on decadal or even centennial timeframes?

US Severe Drought Down 90% Since 1934

Eighty years ago, severe drought covered most of the US, but now covers less than 5% of the country. 

The Worst North American Drought Year of the Last Millennium: 1934

Benjamin I Cook, Richard Seager, and Jason E Smerdon

During the summer of 1934, over 70% of Western North America experienced extreme drought, placing this summer far outside the normal range of drought variability and making 1934 the single worst drought year of the last millennium. Strong atmospheric ridging along the West Coast suppressed cold season precipitation across the Northwest, Southwest, and California, a circulation pattern similar to the winters of 1976–1977 and 2013–2014. In the spring and summer, the drying spread tothe Midwest and Central Plains, driven by severe precipitation deficits downwind from regions of major dust storm activity, consistent with previous work linking drying during the Dust Bowl to anthropogenic dust aerosol forcing. Despite a moderate La Niña, contributions from sea surface temperature forcing were small, suggesting that the anomalous 1934 drought was primarily a consequence of atmospheric [natural] variability, possibly amplified by dust forcing that intensified and spread the drought across nearly all of Western North America.

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