AMS Forum: Climate Change Manifested by Changes in Weather


Extremes and El Nino

Gerald A. Meehl, NCAR, Boulder, CO; and C. Tebaldi

Present-day and future changes of weather and climate extremes typically have been studied for trends and for averages over different time periods. For example, frost days (when night-time minimum temperatures drop below freezing) have been shown to have been decreasing more in the western U.S. compared to the eastern U.S., and they are projected to continue to decrease with that same pattern in a future warmer climate. Heat waves are projected to become more intense on the eastern seaboard, southern and upper Midwest, and across the western U.S. in the future. These changes have been attributed mainly to changes in atmospheric circulation as a change in the base state climate. However, extremes also have distinct patterns associated with El Nino events in present-day climate. Though there is little consistency among models about future changes in El Nino events themselves, there are indications that atmospheric circulation teleconnections over North America associated with El Nino events could weaken in a future warmer climate. Therefore, the patterns of extremes in future El Nino events could change as well, and results are presented regarding such projected changes. .

Session 1, Climate and Extreme Weather Events
Tuesday, 16 January 2007, 1:30 PM-5:30 PM, 214D

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