Climate change has made Britain’s heat wave worse, scientists say

The heat that shattered records in Britain last week, bringing temperatures as high as 104.5 degrees Fahrenheit to a country unaccustomed to scorching summers, would have been ‘extremely unlikely’ were it not for the climate change influence of human origin, a new scientific report released Thursday has 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 recorded last week were 1 in 1,000 in any given year, she and her colleagues found.

Still, said Dr. Zachariah, those temperatures were at least 10 times more likely than they would have been in a world without greenhouse gas emissions, and at least 3.6 degrees Fahrenheit warmer.

“It’s still a rare event today,” said Friederike Otto, a climatologist at Imperial College London and another author of the report. “This would have been an extremely unlikely event without climate change.”

Hot weather has become more frequent and intense in most parts of the world, and scientists have little doubt that global warming is a key factor. As the burning of fossil fuels causes average global temperatures to rise, the range of possible temperatures is also shifting upwards, making searing highs more likely. This means that every heat wave is now compounded, to some extent, by changes in planetary chemistry caused by greenhouse gas emissions.

Before last week, Britain’s highest temperature on record was 101.7 degrees Fahrenheit, or 38.7 degrees Celsius, a milestone set in Cambridge in July 2019. This month, as temperatures were rising, the national meteorological authority, the Met Office, warned Britons to prepare for further highs.

The mercury passed the old record on the morning of July 19 in the village of Charlwood, Surrey, and continued to rise. By the end of the day, 46 weather stations, covering most of England, from London in the southeast to North Yorkshire in the northeast, had recorded temperatures that met or exceeded the previous national record. Other stations broke their own local records of 5 to 7 degrees Fahrenheit.

In response, the trains were slowed down for fear that the steel rails would warp in the heat. Grass fires have spread to homes, shops and vehicles across London in what the city has described as the busiest day for firefighters since World War II. According preliminary analysis using a peer-reviewed methodology.

Last week’s heat report was produced by World Weather Attribution, an alliance of climatologists specializing in rapid studies of extreme weather events to assess how much global warming was behind them. Using computer simulations, scientists are comparing the existing world, in which humans have spent more than a century adding heat-trapping gases to the atmosphere, to a world that might have existed without this activity.

The group’s analysis of the heat in Britain has not yet been peer-reviewed or published in an academic journal, but it relies on peer-reviewed methods.

Using similar techniques, the group found that the heat wave that scorched South Asia this spring was 30 times more likely to occur due to global warming emissions.

Much of Western and Central Europe experienced a very warm start to the summer, driven by an area of ​​high pressure which brought warm air from North Africa. England is experiencing its driest July in over a century. When the ground is dry, the sun’s energy is used to heat the air instead of evaporating water on the ground, which can contribute to even warmer temperatures.

Scientists reported this month that heat waves in Europe have increased 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 climatologists to wonder if extreme temperatures 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 breaking the long jump record by 2 or 3 feet.

So far, however, the 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, also increased the likelihood of heat records being broken by large margins.

The question – as with floods, droughts and other extremes – is whether decision makers will use this knowledge to begin to better prepare in advance.

“Certain conditions usually turn these hazards into disasters, and these conditions are man-made,” said Emmanuel Raju, associate professor of public health at the University of Copenhagen and another author of the Britain heat report. These conditions include poor planning and a lack of attention to vulnerable groups such as the homeless, Dr Raju said.

Vikki Thompson, a climatologist at the University of Bristol, conducted another recent study which found that while extreme temperatures have become more common around the world in recent decades, this could still be largely explained by higher average temperatures caused by climate change. “They increase in intensity, but not faster than average,” Dr. Thompson said.

Yet even this rate of increase is straining the ability of countries to cope. The UK rail system has been designed to operate safely only up to 80.6 degrees Fahrenheit. Most homes were designed to retain heat during freezing winters. Many Britons still see the warm weather as a welcome relief from the cold and humidity.

In Britain, ‘people still don’t take it as seriously as they might next time,’ said Dr Thompson. “A heat wave is, for most people, seen as something great to come. They want some warmth.

“But when it’s 40 degrees,” or 104 degrees Fahrenheit, she says, “it starts to change.”