Sep 27, 2011

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