Changes in Extreme Temperatures Under Increased CO2 in Millennial-Scale Climate Simulations

• Activity Number: 32
• Type: Contributed
• Date/Time: Sunday, August 9, 2015 : 2:00 PM to 3:50 PM
• Sponsor: Section on Statistics and the Environment
• Author(s): Whitney Huang* and Michael L. Stein and Elisabeth Moyer and Shanshan Sun and David McInerney
• Companies: Purdue University and The University of Chicago and The University of Chicago and The University of Chicago and University of Adelaide
• Keywords: GEV ; Extremes ; Temperature ; GCM ; CO2 ; CCSM3

Abstract

It is of great interest to determine how the temperature extremes may be affected by increased atmospheric CO2 levels. However, this inquiry is complicated by the fact that the observational data records are not adequate to robustly detect possible changes in this behavior. We focus on 1000-year equilibrium runs from the Community Climate System Model version 3 (CCSM3) under different CO2 levels. The Generalized Extreme Value (GEV) distribution is fitted to winter minimum and summer maximum temperature using the block maxima approach. The long model runs allow us to better determine the changes in temperature extremes. A comparison of quantile functions of the fitted extreme value distributions for these CO2 levels was performed for each pixel over the contiguous United States. The results suggest that changes in warm extremes generally follow the changes in the mean of summer daily maximum temperature, while cold extremes warm stronger than the mean changes of daily minimum winter temperature nearly everywhere in the contiguous United States. In addition, there is some evidence indicating that the shape parameter may change for some high latitude pixels during winter.