Climate change made UK heatwave at least 10 times more likely: Study

Without human-caused climate change temperatures of 40°C in the UK would have been extremely unlikely, says the analysis

Climate change made the intense heatwave that the UK recently experienced at least 10 times more likely, according to an analysis by a group of international climate scientists at the World Weather Attribution group.

The analysis focused on the maximum temperatures over two days (July 18 and 19) in the UK’s most affected region, an area around central England and east Wales. It found that the frequency and magnitude of such events have increased due to human-caused climate change. On July 19, the UK set a new national record as temperatures reached 40.3°C, 1.6°C warmer than the previous record and 3.6°C hotter than the record that had stood until 1990.

However, scientists note this is a conservative estimate as extreme temperatures in Western Europe have risen more than climate models simulate.

“Even with a conservative estimate, we see a large role of climate change in the UK heatwave. Under our current climate that has been altered by greenhouse gas emissions, many people are experiencing events during their lifetime that would have been almost impossible otherwise. And the longer we take to reach net zero, the worse the heatwaves will become,” said Mariam Zachariah, research associate at the Grantham Institute for Climate Change, Imperial College London, who was part of the research team. 

The UK Met Office issued an extreme heat warning for the first time ever on July 15. To quantify the effect of climate change on the high temperatures in the UK, scientists analysed weather data and computer simulations to compare the climate as it is today—after about 1.2°C of global warming since the late 1800s—with the climate of the past, following peer-reviewed methods.

While models estimate greenhouse gas emissions increased temperatures in this heatwave by 2°C, historical weather records indicate that the heatwave would have been 4°C cooler in a world that had not been warmed by human activities.

“In Europe and other parts of the world we are seeing more and more record-breaking heat waves causing extreme temperatures that have become hotter faster than in most climate models. It’s a worrying finding that suggests that if carbon emissions are not rapidly cut, the consequences of climate change on extreme heat in Europe, which already is extremely deadly, could be even worse than we previously thought,” said Friederike Otto, senior lecturer in Climate Science at the Grantham Institute for Climate Change, Imperial College London, who was one of the researchers in the team. 

The model results suggest that a heatwave as intense as this one is still rare in today’s climate, even after being made more likely by climate change, with a 1% chance of happening each year, in agreement with an earlier study made at the UK Met Office. But weather records again suggest this may be an underestimation with similar heatwaves now more likely to happen than climate models suggest.

Across the world, climate change has made heat waves more common, longer and hotter. A few months ago, parts of India and Pakistan were reeling under unexpected, early and prolonged heat waves. A study found that climate change made such heat waves 30 times more likely in the two countries. Researchers are calling for an escalated pace to net zero in order to minimise the growing risks of greenhouse emissions.  

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