1001 Discussion of Recent Cyclical Temperature Trends Detected in the United States

Wednesday, 10 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
Adam Theisen, Atmospheric Radiation Measurement Data Quality Office/CIMMS/Univ. of Oklahoma, Norman, OK; and D. Sisterson

Annually-averaged Surface temperature data collected at the Atmospheric Radiation Measurement Program Southern Great Plains site (SGP) has shown a strong cyclical trend from 2000 to present. The general trend is a peak in the temperatures every five to six years that has been increasing in magnitude every cycle. The first peak occurred in 2001, and subsequently in 2006 and 2012. If the trend does continue, another peak would be present in 2017 or 2018. Further analysis of the yearly averaged temperatures across the United States has revealed that this cyclical trend is also present in most states East of the Rocky Mountain Range with a slight variation in periodicity based on region. The SGP Site temperature patterns were compared to teleconnection indices for the same time period. While the SGP peaks have been occurring during recent La Nina years, the spatial extent of the anomalies is not fully consistent with what’s been previously observed since 1950 for La Nina events. The upper Midwest states (Minnesota, Dakotas, Montana) have traditionally experienced lower temperatures during past La Nina events but instead have recently experienced the same increasing peaks in annual temperature observed at the SGP. Decreasing sea ice extent in the Northern Hemisphere is also thought to contribute to these trends with the last positive sea ice anomaly occurring in 2001. The expectation of this presentation is to spur discussion on the cause of this cycle and if it’s a real signal. If so, what is the exact mechanism driving it? Are these trends resultant from a new process or a shift in the effects of ENSO or other known oscillations?

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