Atmospheric extremes

Attribution of atmospheric extremes considers both their temporal changes and the occurrence of a specific extreme event. The emphasis is on whether anthropogenic forcing has been sufficient for the extreme to emerge from the background noise of internal variability and, if so, by how much. For temporal changes, it is also important to determine where and when emergence occurs. Hence, the focus is not only on past changes in the extremes but also on their projected evolution. There has been a rapid growth in the evidence showing increasing human influence on both the trends in extremes, and the changes in the frequency and intensity of an individual extreme event. This is particularly the case for temperature and precipitation extremes, droughts and tropical cyclones, as well as for compound extremes such as dry/hot events. The growth in robust evidence reflects not only the recent methodological advances but also the growing realisation of the importance of attribution findings to developing policies and plans for managing the impacts of extremes in the coming years. But the geographical coverage of attribution studies continues to be very patchy, and the types of extremes which have been assessed are insufficiently diverse.