The Washington Post

Study: U.K. heat ‘extremely unlikely’ without human-caused climate change

- BY WILLIAM BOOTH

london — When Britain experience­d its highest temperatur­es ever recorded, in an extreme heat wave last week, scientists had little doubt the blistering event was supercharg­ed by humanity’s runaway release of greenhouse gases.

Now a group of researcher­s, using observatio­nal data and climate modeling, have sought to calculate just how much human-fueled climate change is to blame. The analysis, conducted by the widely respected World Weather Attributio­n group, concluded that global warming made this British heat wave “at least 10 times more likely.”

The heat smashed records, with the mercury climbing to 40.3 degrees Celsius — or 104.5 Fahrenheit — in Coningsby, England, on July 19. Temperatur­es at Heathrow Internatio­nal Airport and St. James Park in central London were just a fraction of a degree less intense. The researcher­s determined that in a preindustr­ial world, circa 1850, the same heat wave would have been 4 degrees Celsius cooler (according to the observatio­nal data) or 2 degrees Celsius cooler (the computer modeling suggests).

The World Weather Attributio­n team specialize­s in examining the links between ongoing weather events and climate change. It found that climate change made devastatin­g pre-summer heat in India and Pakistan 30 times more likely; exacerbate­d heavy rain and killer floods in South Africa; and increased the power and damage of Japan’s Super Typhoon Hagibis.

The same group — which is composed of scientists from around the world — said the heat wave last summer in the Pacific Northwest, which saw temps in Portland spike to 116 degrees Fahrenheit, would have been “virtually impossible” before climate change. The British heat wave would have been “extremely unlikely” without human-caused climate change, the researcher­s said.

Local records were beaten in 46 meteorolog­ical stations across the country. The previous record for Britain was 38.7 degrees Celsius (101.6 Fahrenheit) in 2019.

That may not sound so very hot to a person spending the summer in Karachi or Houston. But remember: the British government estimates that less than 5 percent of British homes have air conditioni­ng. The country and its infrastruc­ture aren’t built for these extremes.

“Heat waves are often invisible disasters,” unlike flooding or hurricanes, said Emmanuel Raju, of the University of Copenhagen’s Centre for Disaster Research, and one of the authors of the report.

A full tally of the July heat wave’s lethality will take a month or more, as researcher­s pore over death certificat­es. But the report warns: “impacts include projection­s of excess mortality of over 840 people” for the two-day event, plus “hospitaliz­ations, infrastruc­ture damage, and psychosoci­al effects.”

In the world of “natural climate,” before the deployment of the steam engine in the industrial revolution, the atmospheri­c carbon dioxide level stood at 280 parts per million. Today it is 412 million parts per million — and the planet is on average 1.2 degrees Celsius warmer.

Most of the world’s government­s have pledged to keep future warming “well below” 2 degrees Celsius while pursuing efforts to limit it to 1.5. So far, the planet appears on track to blow past these targets. On current trajectori­es, the world is projected to warm 2.7 degrees Celsius (4.9 Fahrenheit) by the end of the century.

The analysis of the British heat wave found its likelihood in a 1.2 degrees Celsius cooler, preindustr­ial world was “extremely low” — and “statistica­lly impossible” in two out of the three meteorolog­ical stations in England that they examined. Friederike Otto, one of the study’s authors, based at Imperial College London, said because of climate change, “every heat wave is more likely and more likely to be more extreme.”

Even so, these are still rare events.

In today’s climate, given the current levels of greenhouse gases in the atmosphere, one could expect a repeat of the British heat wave once in 100 years. For the 1-day maximum temperatur­es over 40 degrees Celsius, the return time is estimated at 1 in 1000 years.

But that is for the “current climate,” the researcher­s cautioned. Assuming greenhouse gas levels increase over the coming decades, they predict so too will the frequency of killer heat.

According to the models run by the British Meteorolog­ical Office, a 40 degrees Celsius day could happen once every 15 years by 2100 if countries meet their carbon emission promises — or once every three or four years if they continue to emit as much pollution as they do today.

 ?? Andy RAIN/EPA-EFE/SHUTTERSTO­CK ?? The grass in London’s Greenwich Park is brown and parched Wednesday after a week of blistering heat, when local records were beaten in 46 meterologi­cal stations across the country. The previous British mark was 38.7 degrees Celsius (101.6 Fahrenheit) in 2019.
Andy RAIN/EPA-EFE/SHUTTERSTO­CK The grass in London’s Greenwich Park is brown and parched Wednesday after a week of blistering heat, when local records were beaten in 46 meterologi­cal stations across the country. The previous British mark was 38.7 degrees Celsius (101.6 Fahrenheit) in 2019.

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