Abstract
AbstractExtreme temperature events causing significant environmental and humanitarian impacts are expected to increase in frequency and magnitude due to global warming. The latest generation of climate model projections, Coupled Model Intercomparison Project Phase Six (CMIP6), provides a new and improved database to investigate change in future daily scale extreme temperature events. This study examines the changes in 1, 3, and 5 day averaged annual maximum temperature in four large CMIP6 ensembles. It analyses, using a generalized extreme value (GEV) method, the change in extreme daily mean temperatures at 1.5 and 2°C of global warming, levels highlighted by the 2016 Paris Agreement, and additionally at 3°C. Extremely hot events are characterized using the annual maxima of daily near surface air temperature in the SSP370 scenario. Global changes in the mode of the distributions (location parameter) follow long‐term summer warming and show very similar spatial patterns. Changes in variability (scale parameter) show a clear trend of increases over the tropics and decreases over higher latitudes, while changes to the tails of distributions (shape parameter) show less globally consistent trends but clear signals over the Arctic sea ice, behaviour also seen in variability. Risk ratios (RRs) indicating the change in probability of hot daily extremes that currently have a 10 year return period increase globally with mean temperature change, with greater increases over the tropics. Globally averaged changes in RR over land range from 3.1–3.6 to 7.9–8.3 for 1.5 and 3°C of warming, respectively. For the latter case, this indicates previously rare, once‐in‐a‐decade summer extremes will occur almost annually in the future under high warming.
Highlights
Anthropogenic warming has been shown to enhance heat extremes, with recent events such as the 2019 record heat in France being, to a substantial fraction, attributed to the effects of human driven emissions (Vautard et al, 2020)
We have used large ensemble models from the CMIP6 model inter-comparison project to investigate the change in extreme temperature events at 1.5, 2, and 3C of global warming
Using the SSP370 emissions scenario to obtain the largest number of ensemble members, the future model simulations were compared to the last decade of historical runs, which were in turn related to the estimated difference between that decade and the period 1850–1900
Summary
Anthropogenic warming has been shown to enhance heat extremes, with recent events such as the 2019 record heat in France being, to a substantial fraction, attributed to the effects of human driven emissions (Vautard et al, 2020). Using output from Phase 6 of the Coupled Model Intercomparison Project (CMIP6), we explore changes in annual maximum temperatures, characterizing them using the generalized extreme value (GEV) distribution.
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