Increase of extreme events in a warming world

Stefan Rahmstorf and Dim Coumou

Proceedings of the National Academy of Sciences

Develops a theoretical approach to quantify the effect of long-term trends on the expected number of extremes in generic time series, using analytical solutions and Monte Carlo simulations
Applies the method to study the effect of warming trends on heat records
Finds that the number of record-breaking events increases approximately in proportion to the ratio of warming trend to short-term standard deviation
Finds that short-term variability thus decreases the number of heat extremes, whereas a climatic warming increases it
For extremes exceeding a predefined threshold, the dependence on the warming trend is highly nonlinear
Finds that the sum of warm plus cold extremes increases with any climate change, whether warming or cooling
Estimates that climatic warming has increased the number of new global-mean temperature records expected in the last decade from 0.1 to 2.8
Estimates for July temperature in Moscow that the local warming trend has increased the number of records expected in the past decade fivefold, which implies an approximate 80% probability that the 2010 July heat record would not have occurred without climate warming