Evaluating heat extremes in the UK Climate Projections (UKCP18)

TY - JOUR

T1 - Evaluating heat extremes in the UK Climate Projections (UKCP18)

AU - Kennedy-Asser, A. T.

AU - Andrews, O.

AU - Mitchell, D. M.

AU - Warren, R. F.

N1 - Funding Information: AKA, OA and RW acknowledge support from UK Natural Environment Research Council (NERC) grant NE/S017267/1. We acknowledge the UK Meteorological Office for their work in preparing and making available the UKCP18 and HadUK-Grid data. ERA5 data was generated using Copernicus Climate Change Service information (2020). Publisher Copyright: © 2020 The Author(s). Published by IOP Publishing Ltd.

PY - 2021/1/5

Y1 - 2021/1/5

N2 - In recent years, UK summer heatwaves have resulted in thousands of excess deaths, with both extreme temperatures and high humidity increasing health risks. Here, the UK Climate Projections 2018 (UKCP18) are compared to observational (HadUK-Grid) and reanalysis data (ERA5) to quantify model performance at capturing mean, extremes (95th to 99.5th percentiles) and variability in the climate state and heat stress metrics (simplified wet bulb global temperature, sWBGT; Humidex; apparent temperature). Simulations carried out for UKCP18 generally perform as well as or better than CMIP5 models in reproducing observed spatial patterns of UK climate relating to extreme heat, with RMSE values on average ∼30% less than for the CMIP5 models. Increasing spatial resolution in UKCP18 simulations is shown to yield a minor improvement in model performance (RMSE values on average ∼5% less) compared to observations, however there is considerable variability between ensemble members within resolution classes. For both UKCP18 and CMIP5 models, model error in capturing characteristics of extreme heat generally reduces when using heat stress metrics with a larger vapour pressure component, such as sWBGT. Finally, the 95th percentile of observed UK summer temperature is shown to have ∼60% greater interannual variability than the summer mean over the recent past (1981–2000). This effect is underestimated in UKCP18 models (∼33%) compared to HadUK-grid and ERA5. Compared to projected future changes in the global mean temperature, UK summer mean and 95th percentile temperatures are shown in increase at a faster rate than the global mean.

AB - In recent years, UK summer heatwaves have resulted in thousands of excess deaths, with both extreme temperatures and high humidity increasing health risks. Here, the UK Climate Projections 2018 (UKCP18) are compared to observational (HadUK-Grid) and reanalysis data (ERA5) to quantify model performance at capturing mean, extremes (95th to 99.5th percentiles) and variability in the climate state and heat stress metrics (simplified wet bulb global temperature, sWBGT; Humidex; apparent temperature). Simulations carried out for UKCP18 generally perform as well as or better than CMIP5 models in reproducing observed spatial patterns of UK climate relating to extreme heat, with RMSE values on average ∼30% less than for the CMIP5 models. Increasing spatial resolution in UKCP18 simulations is shown to yield a minor improvement in model performance (RMSE values on average ∼5% less) compared to observations, however there is considerable variability between ensemble members within resolution classes. For both UKCP18 and CMIP5 models, model error in capturing characteristics of extreme heat generally reduces when using heat stress metrics with a larger vapour pressure component, such as sWBGT. Finally, the 95th percentile of observed UK summer temperature is shown to have ∼60% greater interannual variability than the summer mean over the recent past (1981–2000). This effect is underestimated in UKCP18 models (∼33%) compared to HadUK-grid and ERA5. Compared to projected future changes in the global mean temperature, UK summer mean and 95th percentile temperatures are shown in increase at a faster rate than the global mean.

KW - Climate

KW - Heat stress

KW - Heatwaves

KW - Model evaluation

KW - UKCP18

UR - http://www.scopus.com/inward/record.url?scp=85099398402&partnerID=8YFLogxK

U2 - 10.1088/1748-9326/abc4ad

DO - 10.1088/1748-9326/abc4ad

M3 - Article

AN - SCOPUS:85099398402

SN - 1748-9318

VL - 16

JO - Environmental Research Letters

JF - Environmental Research Letters

IS - 1

M1 - 014039

ER -