Future risk of record-breaking summer temperatures and its mitigation

Flavio Lehner,Clara Deser,Benjamin M Sanderson

doi:10.1007/s10584-016-1616-2

Abstract

The probability that summer temperatures in the future will exceed the hottest on record during 1920–2014 is projected to increase at all land locations with global warming. Within the BRACE project framework we investigate the sensitivity of this projected change in probability to the choice of emissions scenario using two large ensembles of simulations with the Community Earth System Model. The large ensemble size allows for a robust assessment of the probability of record-breaking temperatures. Globally, the probability that any summer during the period 2061–2081 will be warmer than the hottest on record is 80 % for RCP 8.5 and 41 % for RCP 4.5. Hence, mitigation can reduce the risk of record-breaking temperatures by 39 %. The potential for risk reduction is greatest for some of the most populated regions of the globe. In Europe, for example, a potential risk reduction of over 50 % is projected. Model biases and future changes in temperature variance have only minor effects on the results, as their contribution stays well below 10 % for almost all locations.

Highlights

The frequency and intensity of heat waves or extremely warm summers is expected to increase as anthropogenically-driven global warming progresses (Coumou et al 2013; Russo et al 2014)
To put the σ changes in Community Earth System Model (CESM) into a larger perspective, we have examined σ changes in 26 models participating in the fifth Coupled Model Intercomparison Project (CMIP5) using the period 2061–2080 from the RCP8.5 simulations compared to the historical period 1920–2014
This study investigates the probability that summers in the future will be as warm or warmer than the hottest on record during 1920–2014, based on large ensembles of simulations with CESM under Representative Concentration Pathways (RCPs) 4.5 and RCP 8.5 emissions scenarios

Summary

Introduction

The frequency and intensity of heat waves or extremely warm summers is expected to increase as anthropogenically-driven global warming progresses (Coumou et al 2013; Russo et al 2014) Potential impacts of such high temperature events range from health effects (Anderson et al 2015, accepted; Marsha et al 2015, submitted) to drought occurrence (Towler et al 2015, submitted) and agricultural losses (Battisti and Naylor 2009; Levis et al 2015, submitted). Recent examples of fatal heat waves and food crises linked to record-breaking summer temperatures can serve as case studies for a potential future norm We revisit this issue, using a new generation of climate model simulations and focusing on potential benefits from climate mitigation in light of different emission scenarios

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Conclusion