Robustness of climate change signals in near term predictions up to the year 2030: Changes in the frequency of temperature extremes

This is the first study to examine whether human contributions to changes in extreme temperature indices have larger amplitudes than natural variability in near future (up to 2030) climate prediction. We performed 10 runs of the initial condition perturbed ensemble of a coupled atmosphere-ocean general circulation model. In the near future, over most land areas, all 10 runs predict more frequent occurrences of warm nights and warm days, and less frequent cold nights and cold days, suggesting that human influences have become larger than natural variability. The fraction of areas where all runs agree on the direction of changes over land is less sensitive to ensemble sizes (for warm nights, 96% and 93% for 4 runs and 10 runs, respectively). The changes in the frequency of warm and cold extremes are mainly due to shifts in seasonal mean temperatures. Additionally snow cover affects the frequency of cold extremes in some areas.