92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Wednesday, 25 January 2012
Alternate Estimates of CLIMATE Projections for Southeast USA
Hall E (New Orleans Convention Center )
James Obrien, Florida State University, Tallahassee, FL

. Many projections of future climate, especially those in the IPCC fourth assessment, are for changes in the next 100 years or and based upon the highly uncertain output of Global Climate Models. The disconnect is that stakeholders need climate information that is tailored to their planning horizon (20 to 30 years), without the biases and problems associated with the model output, and local or regional in scope. We propose that one source of climate information for climate change assessments can be gleaned from our historic climate record of surface observations. Rather than rely on downscaled global climate model output for future climate scenarios, we make use of observations from the historic climate record as an example of what may be possible under a changing climate. The advantages of using historic climate analogs as future scenarios are because they are a record of our actual climate in the past, these analogs preserve the known variability of our regional climate from year to year changes to those lasting several decades. The historic analogs are not approximations of physical processes or model representations of atmospheric circulation and pressure patterns. They are actual measurements of the way our climate system is known to behave and are physically consistent with all atmospheric physics on all scales. Thirdly, the observations are local, made daily at actual surface weather stations across the Southeast. Looking at the long-term temperature records of the Southeast U.S. provides a justification for using this approach. Average annual temperatures since 1895 show distinct decades of predominantly warmer temperatures (1920's through 1950's) and cooler temperatures (1960's through 1980's), The weather observations are parsed into three different 20-year analog scenarios. The first represents a “warm” scenario, when average temperatures across the Southeast were 1 to 3 degrees F. warmer than recent temperatures. This scenario represents a reasonable estimate of climatic conditions in the next 20-30 years if, in fact, the Southeast were to warm from the influence of anthropogenic climate change. The years chosen for the warm scenario are 1935-1954. The second represents a “cold” scenario, where temperatures were 1-3 degrees F colder than recent temperatures on average and the years chosen were 1958-1977. The cold scenario can be useful in framing the range of plausible climatic conditions possible in the next 20-30 years. The third scenario represents a “modern” climate from the years 1981-2000.

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