The heat that demolished Britain’s records last week, bringing temperatures as high as 104.5 degrees Fahrenheit to a country unaccustomed to scorching summers, would have been “extremely unlikely” without the influence of man-made climate change, a new report scientific released on Thursday found.
The heat of last week’s intensity is still highly unusual for Britain, even at current levels of global warming, said Mariam Zachariah, a research associate at Imperial College London and lead author of the new report. The odds of seeing the daytime highs that some parts of the country saw last week were 1 in 1,000 in any given year, she and her colleagues found.
Still, said Zachariah, those temperatures were at least 10 times more likely than they would be in a world with no greenhouse gas emissions, and at least 3.6 degrees Fahrenheit warmer.
“It’s still a rare event today,” said Friederike Otto, a climate scientist at Imperial College London and another author of the report. “It would have been an extremely unlikely event without climate change.”
Severe heat has become more frequent and intense in most regions of the world, and scientists have little doubt that global warming is a major factor. As the burning of fossil fuels causes global average temperatures to rise, the range of possible temperatures also increases, making highs more likely more likely. This means that each heat wave is now exacerbated, to some degree, by changes in planetary chemistry caused by greenhouse gas emissions.
Prior to last week, the highest temperature Britain had ever recorded was 101.7 Fahrenheit, or 38.7 Celsius, a benchmark set in Cambridge in July 2019. high.
Mercury passed the old record on the morning of July 19 in the village of Charlwood, Surrey, and continued to rise. Later in the day, 46 weather stations, spanning most of England, from London in the southeast to North Yorkshire in the northeast, recorded temperatures that reached or exceeded the previous national record. Other stations beat their own local records by 5 to 7 degrees Fahrenheit.
In response, trains were slowed down for fear that the steel tracks might bend in the heat. Grass fires spread to London homes, shops and vehicles in what the city described as the Fire Department’s busiest day since World War II. More than 840 people may have died in England and Wales than would be normal, according to preliminary analysis using peer-reviewed methodology.
Last week’s heat report was produced by the World Weather Attribution, an alliance of climate scientists specializing in rapid studies of extreme weather events to assess the degree to which global warming was behind them. Using computer simulations, the scientists compare the existing world, in which humans have spent more than a century adding heat-trapping gases to the atmosphere, to a world that might not have such activity.
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The group’s analysis of heat in Britain has not yet been peer-reviewed or published in an academic journal, but is based on peer-reviewed methods.
Using similar techniques, the group found that the heat wave that ravaged South Asia this spring was 30 times more likely to occur due to planet-warming emissions.
Much of Western and Central Europe had a very hot start to summer, driven by an area of high pressure that brought in warm air from North Africa. England is having its driest July in over a century. When the soil is parched, the sun’s energy goes into heating the air instead of evaporating the water in the soil, which can contribute to even warmer temperatures.
Scientists reported this month that heat waves in Europe have grown in frequency and intensity over the past four decades, at least in part due to changes in the jet stream.
For some scientists, Britain’s recent heat has brought to mind last summer’s deadly temperatures in the Pacific Northwest, which broke records in some places by 7 degrees Fahrenheit or more. This heat was so unusual that it led some climate researchers to wonder whether hot extremes were appearing faster than their scientific models explained. It was the climate equivalent, said Erich Fischer of the Swiss university ETH Zurich, of an athlete who broke the record for the long jump by 2 or 3 feet.
So far, however, evidence suggests that such events are surprising, but not unpredictable, using current models. Dr. Fischer led a study last year that showed that global warming, with its seemingly small increases in average temperatures, was also making heat records more likely to be broken by large margins.
The question – as well as floods, droughts and other extremes – is whether policymakers will use this knowledge to start preparing better in advance.
“There are conditions that often turn these hazards into disasters, and those conditions are man-made,” said Emmanuel Raju, associate professor of public health at the University of Copenhagen and another author of the report on heat in Britain. These conditions include poor planning and a lack of attention to vulnerable groups such as homeless people, Raju said.
Vikki Thompson, a climate scientist at the University of Bristol, led a different recent study that found that while heat extremes were becoming more frequent around the world in recent decades, most of this could still be explained by higher average temperatures. highs caused by climate change. “They are increasing in intensity, but not faster than average,” said Dr. Thompson.
However, even this rate of increase is straining countries’ ability to cope. Britain’s rail system is designed to work safely only up to 80.6 degrees Fahrenheit. Most homes are designed to retain heat during freezing winters. Many Britons still see warm weather as a welcome relief from the cold and damp.
In Britain, “people are still not taking this as seriously as maybe next time,” said Dr. Thompson. “A heat wave is, by most people, thought of as a great thing to happen. They want some heat.”
“But when it’s 40 degrees,” or 104 Fahrenheit, she said, “that starts to change.”