Climate change impacts on extreme events in the United States: an uncertainty analysis

Erwan Monier,Xiang Gao

doi:10.1007/s10584-013-1048-1

Abstract

In this study, we analyze changes in extreme temperature and precipitation over the US in a 60-member ensemble simulation of the 21st century with the Massachusetts Institute of Technology (MIT) Integrated Global System Model–Community Atmosphere Model (IGSM-CAM). Four values of climate sensitivity, three emissions scenarios and five initial conditions are considered. The results show a general intensification and an increase in the frequency of extreme hot temperatures and extreme precipitation events over most of the US. Extreme cold temperatures are projected to decrease in intensity and frequency, especially over the northern parts of the US. This study displays a wide range of future changes in extreme events in the US, even simulated by a single climate model. Results clearly show that the choice of policy is the largest source of uncertainty in the magnitude of the changes. The impact of the climate sensitivity is largest for the unconstrained emissions scenario and the implementation of a stabilization scenario drastically reduces the changes in extremes, even for the highest climate sensitivity considered. Finally, simulations with different initial conditions show conspicuously different patterns and magnitudes of changes in extreme events, underlining the role of natural variability in projections of changes in extreme events.

Highlights

Extreme weather and climate events, such as heat waves, droughts and severe precipitation events, have received increasing attention in recent years, due to the often-largeElectronic supplementary material The online version of this article contains supplementary material, which is available to authorized users
We analyze changes in extreme events from 60 IGSM-Community Atmosphere Model (CAM) simulations of climate change used in a multi impact model project to achieve consistent evaluation of climate change impacts in the US
The results show a general intensification and increase in the frequency of extreme hot temperatures and extreme precipitation events over most of the US

Summary

Introduction

Extreme weather and climate events, such as heat waves, droughts and severe precipitation events, have received increasing attention in recent years, due to the often-largeElectronic supplementary material The online version of this article (doi:10.1007/s10584-013-1048-1) contains supplementary material, which is available to authorized users. Regional and global analyses of temperature extremes on land report statistically significant increases in the numbers of warm days and nights and decreases in the numbers of cold days and nights (Brown et al 2008; Peterson et al 2008; Meehl et al 2009). There have been increases in the number of heavy precipitation events over the last half of the 20th century in more regions than there have been decreases (IPCC 2013). Models project substantial increases in temperature extremes by the end of the 21st century with the length, frequency, and/or intensity of warm spells and heat waves increasing over most land areas (Kharin et al 2007; Sterl et al 2008; Orlowsky and Seneviratne 2012). There are large uncertainties related to GCMs, RCMs and statistical downscaling methods, and by natural variability of the climate (Tebaldi et al 2006; Kharin et al 2007; Kyselyand Beranova 2009; Kenyon and Hegerl 2010; Orlowsky and Seneviratne 2012)

Methods

Results

Conclusion