Historical Changes in Global Extreme Precipitation in Climate Models and Observations

Wednesday, 17 December 2014
Behzad Asadieh and Nir Krakauer, CUNY City College, New York, NY, United States
Precipitation events are expected to become substantially more intense under global warming, but few global comparisons of observations and climate model simulations are available to constrain predictions of future changes in precipitation extremes. We present a systematic comparison of changes in historical annual-maximum daily precipitation between station observations (archived in HadEX2) and the suite of global climate models contributing to the fifth phase of the Coupled Model Inter-comparison Project (CMIP5), from 1901 to 2010 in global scale. We use both parametric and non-parametric tests to quantify the strength of trends in extreme precipitation in observations and models, taking care to spatial and temporal sample them both in comparable ways. We find that both observations and models show generally increasing trends in extreme precipitation since 1901 with larger changes in tropical zones, although annual-maximum daily precipitation has increased faster in the observations than in most of the CMIP5 models. Global average of observational annual-maximum daily precipitation has increased by approximately 10% per degree kelvin of global warming since 1901 which is larger than the average of climate models with 8.3%/K. The rate of increase in extreme precipitation per kelvin of warming in both models and observations are higher than the rate of increase in atmospheric water vapor content per kelvin of warming expected from the Clausius-Clapeyron equation.