Abstract
As European heatwaves become more severe, summers in the United Kingdom (UK) are also getting warmer. The UK record temperature of 38.7 °C set in Cambridge in July 2019 prompts the question of whether exceeding 40 °C is now within reach. Here, we show how human influence is increasing the likelihood of exceeding 30, 35 and 40 °C locally. We utilise observations to relate local to UK mean extremes and apply the resulting relationships to climate model data in a risk-based attribution methodology. We find that temperatures above 35 °C are becoming increasingly common in the southeast, while by 2100 many areas in the north are likely to exceed 30 °C at least once per decade. Summers which see days above 40 °C somewhere in the UK have a return time of 100-300 years at present, but, without mitigating greenhouse gas emissions, this can decrease to 3.5 years by 2100.
Highlights
As European heatwaves become more severe, summers in the United Kingdom (UK) are getting warmer
Our study demonstrates that human-caused climate change has set hot-day extremes in the UK on a course towards temperatures that would be too high to be observed in the natural climate
New records are expected in coming decades, with the most severe extremes likely to occur in the southeast of the UK
Summary
As European heatwaves become more severe, summers in the United Kingdom (UK) are getting warmer. A year later, during a severe heatwave in western Europe[13], the warmest daily temperature averaged over the UK reached a new peak (Fig. 1a) and the highest temperature in the country ever recorded was registered in Cambridge These consecutive summer extremes are exposing the UK’s vulnerability to such weather with ensuing impacts highlighted in the media, including a mortality spike in tandem with the 2019 event[14,15], and a sharp heatwave-driven fall in overseas holiday demand that might have contributed to the collapse of the Thomas Cook travel group[16]. The need to understand how the likelihood of extremely hot temperatures is changing under the anthropogenic effect on the climate is pressing and essential to decision-makers planning the UK’s adaptation strategy To respond to this need, we compute observed and modelled values of the warmest daily maximum temperature in individual years (tx01) and estimate how the likelihood of exceeding extreme thresholds has been changing since 1900 and how it may further change in the remaining of this century under different emission scenarios[17]. The likelihood of exceeding 40 °C anywhere in the UK in a given year has been rapidly increasing, and, without curbing of greenhouse gas emissions, such extremes could be taking place every few years in the climate of 2100
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