Comparing the impacts of mitigation versus non-intervention scenarios on future temperature and precipitation extremes in the HadGEM2 climate model

Although international climate change negotiations focus on global mean temperature targets, it is also important to assess the impact of emission scenarios on climate extremes at the global and regional scale. This paper examines how temperature and precipitation extremes indices are projected to change around the globe during the 21st Century under an aggressive climate change mitigation scenario in the United Kingdom Met Office Hadley Centre HadGEM2-AO coupled climate model, and how these changes might differ from a mid-range non-intervention scenario. Even under an aggressive mitigation strategy there are projected increases in warm temperature extremes on a global and regional scale up to the mid-21st Century, and temperature extremes tend to follow a similar trajectory to the projected global mean temperature change associated with each scenario. Changes in precipitation-related extremes are projected to be more variable. There are regional differences in the direction of changes and it appears that the aerosol forcing associated with the scenarios could have an important influence. The regions which are projected to benefit most from mitigation vary depending on the index being considered, but in general absolute increases in temperature extremes are reduced in the northern midlatitudes, whereas for frequency based indices it is northern South America, parts of the USA, Africa and Asia which see the largest avoided increases. For precipitation indices, northern South America sees the most consistent signal toward avoided drying conditions, along with the Mediterranean and parts of Russia and central Asia.