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Temperatures exceeding 40°C may be reached somewhere in the UK every 3.5 to 15 years by 2100 under continued greenhouse gas emissions, suggests a modelling study in Nature Communications. The paper reports that anthropogenic emissions are increasing the likelihood of extremely warm days in the UK (particularly in the southeast), with temperatures becoming more likely to exceed 30, 35 and 40°C by the end of the century in different parts of the country.
In 2019, Western Europe experienced a severe heatwave, which resulted in the UK recording its highest ever temperature (38.7°C in Cambridge). This raises the question of whether temperatures may exceed 40°C in the future.
Nikolaos Christidis and colleagues estimated changes in the likelihood of extreme temperatures occurring locally in the UK in a series of modelling experiments, looking at medium- (RCP 4.5) and high-emissions (RCP 8.5) scenarios.
The authors found that the change in frequency of exceeding different temperature thresholds depends strongly on the emissions scenario, with higher emissions leading to these events occurring more often over larger areas. They report that temperatures above 35°C are becoming increasingly common, especially in the southeast, and could occur every year by the end of the century, compared to every five years today.
Many areas of the north of the UK, which rarely experience extreme warm temperatures today, are likely to see temperatures exceeding 30°C up to once a decade by 2100. Currently, reaching temperatures of 40°C or more somewhere in the UK is extremely rare and estimated to only occur every 100–300 years.
However, the authors show that this could change to every 15 years under a medium-emissions scenario, and every 3.5 years under high emissions by the end of the century.