Climate change made UK’s record July heatwave 10 times more likely, scientists warn

Human-caused climate change made last week’s record-breaking heatwave at least 10 times more likely, according to rapid attribution analysis released today by an international team of climate scientists.

The group, dubbed the World Weather Attribution Group, concluded that July’s sweltering heat across Europe – which surpassed the 40C mark for the first time on record in parts of England last week – was likely driven by changes in the climate caused by gas emissions, while also stressing that this is a conservative estimate.

For the first time ever, the Met Office issued an extreme heat warning on 15 July. The prolonged period of heat prompted widespread disruption to transport and infrastructure, as well as leading to a spate of wildfires and house fires, particularly across the South East of England.

The number of heat-related deaths is also likely to have ticked-up during the period, as they have during past UK heatwaves, but the official statistics are not set to be released for several weeks.

To quantify the effect of climate change on the high temperatures in the UK in July, the scientists analyzed 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.

The analysis focused on the maximum temperatures over two days 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 has increased due to human-caused climate change.

However, determining the exact contribution of climate change remains challenging, as extreme heat in Western Europe has increased more than estimated by climate models, according to the scientists, who warned that current models may be underestimating the real impact of human-caused climate change. on high temperatures in the UK and Western Europe.

Friederike Otto, senior lecturer in climate science at the Grantham Institute for Climate Change at Imperial College London – and one of the scientists which contributed to the analysis – said that the UK and Western Europe were now seeing more and more record-breaking heatwaves, and that this was 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 had previously thought,” Otto warned.

The sweltering weather in the UK has also coincided with an extended dry period, promoting the rising concern that the country could be officially classed as in ‘drought’ this summer. The past month has marked the dries July on record in England since 1911, with 15.8mm of rain across the country, according to the Met Office.

Earlier this week, the Environment Agency alongside industry bodies and water companies met to discuss the next course of action, as it recommended the public take care to save on water use where possible, but stopped short of taking more drastic action, such as imposing a hosepipe ban.

Another of the scientists Mariam Zachariah – research associate at the Grantham Institute for Climate Change at Imperial College London – said that the worsening impacts of climate change on the UK underscored the urgency of decarbonising the economy to net zero.

“Even with a conservative estimate, we see a large role of climate change in the UK heatwave,” she said. “Under our current climate that has been altered by greenhouse gas emissions, many people are experiencing events during their that would have been almost impossible otherwise. And the longer we take to reach net zero, the worse the lifetime heatwaves will become.”

It follows sobering warnings from the Met Office yesterday that higher temperatures should now be considered in the new normal in the UK.

The weather and climate agency’s annual State of the Climate Report relatively concludes that while the UK experienced a low peak temperature in 2021 compared to other recent years, it was still significantly warmer than the average hottest day of the year prior to 1990, underscoring the speed and scale of the changing climate over the past several decades.

“While the year 2021 would be considered near normal compared to the last three decades, before 1990 a year like this would be the second warmest in our national series that began in 1884,” the report states.

However, in the context of record temperatures recorded since 1990, the 32.2C high temperature recorded in 2021 made it a “relatively unremarkable year”, the report states – although 2022 has already far surpassed that temperature with last week’s 40C heatwave.

Meanwhile, the Met Office’s also notes that sea levels around the British Isles have risen by around 16.5cm on average since 1900, and are now rising by 3mm to 5.2mm a year – more than double the rate of increase in the early part of last century.

The State of Climate report also highlights the variability of weather in the UK, with Storm Arwen in November, Storm Darcy in February, a new Northern Ireland temperature record in July and exceptional rain in October all reviewed by the Met Office in the context of the UK’s changing climate.

“As ever the weather we experienced in 2021 was highly variable, with extreme events like Storm Arwen bringing impacts to our daily lives,” said the report’s lead author Mike Kendon, a climate information scientist at the Met Office National Climate Information Centre. “When considering the UK climate over the whole year it might seem rather unremarkable, however it is telling that when we consider 2021 as near-average for temperature in the context of the current climate, had this occurred just over three decades ago it would have been one of the UK’s warmest years on record.”

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