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Long-Term Trends in Southern Plains Drought. John W. Nielsen-Gammon Texas State Climatologist Texas A&M University n-g@tamu.edu. Definitions. Long-term: between 2 and 50 years from now Trends: changes in expected frequency, duration, or intensity Causes considered here: Global warming
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Long-Term Trends in Southern Plains Drought John W. Nielsen-Gammon Texas State Climatologist Texas A&M University n-g@tamu.edu
Definitions • Long-term: between 2 and 50 years from now • Trends: changes in expected frequency, duration, or intensity • Causes considered here: • Global warming • Natural ocean variability (ENSO, etc.)
Key elements of drought • Too little rainfall • Too much evaporation (too hot) • For too long
No big trend; what about variability? • Mixed signals from the historical record • Mixed signals from climate models • Changes to La Niña expected • Might become more common or intense • Might become less common or intense
Left: observations. Right: projected change in annual precipitation variability (teal=increase, orange=decrease) from two climate models [Wetherald 2009].
Pacific Texas Atlantic
Long-Term Trends • Temporary period of reduced rainfall • Similar to 1950s! • A few more short droughts, or a long one? • Permanent period of increasing temperature • Higher evaporation • Reduced streamflow, reservoir levels • Greater water demand • Intensified drought
Contact Information • John W. Nielsen-Gammon • n-g@tamu.edu • http://atmo.tamu.edu/osc • http://blog.chron.com/climateabyss • 979-862-2248
Control Warming PDO Residual Wang et al. (2009)