August 14, 2022

People sleep in a cooling shelter set up during an unprecedented heat wave in Portland, Oregon, the United States, June 27, 2021.

Maranie Staab | Reuters

SANTA MONICA, California – The deadly heat wave that hit triple-digit temperatures in the Pacific Northwest and Western Canada, killing hundreds of people, was virtually impossible without man-made climate change, according to a new analysis by an international team of 27 scientists.

The temperature records were so extreme – 116 degrees Fahrenheit in Portland, Oregon and 121 degrees Fahrenheit in Canada’s British Columbia – that researchers said it was difficult to quantify how rare the heat wave was. The team working under the umbrella of Oxford University’s World Weather Attribution estimated it was a once-in-a-millennium event.

The scientists from the United States, Canada, United Kingdom, the Netherlands, France, Germany, and Switzerland estimated that human-made climate change increased the likelihood of such a heatwave by at least 150 times.

“An event like the heat wave in the Pacific Northwest in 2021 is still rare or extremely rare in today’s climate, but would be practically impossible without human-made climate change,” wrote the team of scientists. “As the warming continues, it will become much rarer.”

Researchers called for adaptation measures that address the increasing risk of heat waves, including action plans with early warning systems for high temperatures, as well as more ambitious targets to drastically reduce the greenhouse gas emissions that warm the planet.

The researchers also found that in a world with a warming of 2 degrees Celsius, which could occur this century without a significant reduction in greenhouse gas emissions, such a heat event would occur roughly every five to ten years.

According to the World Meteorological Organization, the earth has already warmed up by more than 1 degree Celsius compared to the pre-industrial level.

World Weather Attribution’s analysis, which performs rapid analyzes to determine whether there is a relationship between climate change and certain extreme weather events, has not yet been peer-reviewed. However, it uses processes that have been peer reviewed for the past 10 years.

Scientists used computer simulations that compared a hypothetical world with no greenhouse gas emissions to the existing world to estimate the effects of climate change on weather events. The research is later published in peer-reviewed journals.

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The study, released on Wednesday, is in line with previous research on the effects of climate change on the frequency and severity of heat waves and droughts.

The most recent historic heat wave, which began in late June, resulted in forest fires, threatened water scarcity, and resulted in hundreds of deaths in Oregon, Washington, and British Columbia. The official death toll is expected to rise.

Experts say more than a third of global heat-related deaths during warm seasons are due to climate change. Heat also kills more people than any other weather-related disaster in the US

“Our results are an urgent warning: Our rapidly warming climate is breaking new ground that has significant consequences for health, well-being and livelihoods,” the scientists write.

North America just had its hottest June, according to scientists at the Copernicus Climate Change Service, with 2021 almost certainly going to be one of the 10 hottest years on record.