Benefits of mitigation for future heat extremes under RCP4.5 compared to RCP8.5

Abstract

Using ensembles from the Community Earth System Model (CESM) under a high and a lower emission scenarios, we investigate changes in statistics of extreme daily temperature. The ensembles provide large samples for a robust application of extreme value theory. We estimate return values and return periods for annual maxima of the daily high and low temperatures as well as the 3-day averages of the same variables in current and future climate. Results indicate statistically significant increases (compared to the reference period of 1996-2005) in extreme temperatures over all land areas as early as 2025 under both scenarios, with statistically significant differences between them becoming pervasive over the globe by 2050. The substantially smaller changes, for all indices, produced under the lower emission case translate into sizeable benefits from emission mitigation: By 2075, in terms of reduced changes in 1-day heat extremes, about 95 % of land regions would see benefits of 1°C or more under the lower emissions scenario, and 50 % or more of the land areas would benefit by at least 2°C. 6 % of the land area would benefit by 3°C or more in projected extreme minimum temperatures and 13 % would benefit by this amount for extreme maximum temperature. Benefits for 3-day metrics are similar. The future frequency of current extremes is also greatly reduced by mitigation: by the end of the century, under RCP8.5 more than half the land area experiences the current 20-year events every year while only between about 10 and 25 % of the area is affected by such severe changes under RCP4.5.Climatic Change

Projected Changes in Temperature Extremes in China Using PRECIS

“…The frequency and intensity of cold extremes would decrease in the future, while they are projected to increase significantly in the warm extremes. Therefore, it is necessary to reduce GHG emissions and take adaptation measures to control the increase in the warm events [22,42].…”

Changes in extremely hot days under stabilized 1.5 and 2.0 °C global warming scenarios as simulated by the HAPPI multi-model ensemble

“…Originally introduced by Zwiers and Kharin (1998) and Kharin and Zwiers (2000) to provide statistically rigorous projections of future extreme temperature and precipitation, such GEV analyses, both stationary and non-stationary, are now widespread throughout the literature including recent assessment reports of the International Panel on Climate Change (Seneviratne et al, 2012;Collins et al, 2013). The particulars of the details of the GEV analysis used in this study are described in the Supplement of Tebaldi and Wehner (2018).…”

Community climate simulations to assess avoided impacts in 1.5 and 2 °C futures

“…We can consider the spatial distribution of extreme temperature events by following the methodology of Tebaldi and Wehner (2016), which fits a generalized extreme value (GEV) distribution to the upper tail of 3-day temperature averages for both the historical period in this case) and the future (2071-2100) under different scenarios. The GEV is used to assess, historically, the 3-day average temperature which would be considered a 1-in-20-year event.…”