A New Global Set of Downscaled Temperature Scenarios

Abstract

new set of empirical?statistical downscaled seasonal mean temperature scenarios is presented for locations spread across all continents. These results are based on the Coupled Model Intercomparison Project phase 3 (CMIP3) simulations, the Special Report on Emissions Scenarios (SRES) A1B story line, and arguably represent the largest downscaled multimodel ensemble to date in terms of worldwide distribution, length of time interval, and the number of global climate model simulations. The ensemble size of ?50 members enables a crude uncertainty analysis for simulated future local temperature, and maps have been constructed for Europe, Africa, and the northwestern part of Russia and Scandinavia of the ensemble mean and 95th percentile for seasonal mean temperatures projected for 2100, as well as simulated probabilities for low or high temperatures. The results are stored as matrices of coefficients describing best-fit fifth-order polynomials, used to approximate the long-term trends in the temperature. These results suggest that the 95th percentile of the summer temperature is expected to increase 3°?5°C by 2100 over most of Europe, and that there will be reduced probabilities of winter temperature lower than 0°C for all European locations, with the greatest reduction of ?60% in areas where the winter temperature presently is around freezing point. A similar analysis for Africa suggests that the June?August mean temperatures may exceed 35°C in isolated regions by 2100. For the northwestern part of Russia and Scandinavia, the analysis yields a 4.5°?7.5°C increase for the ensemble mean December?February temperature, with the most pronounced warming in the northeast, north, and over Finnmark County in Norway.