Record-breaking heat wave grips western United States

A record early heat wave striking the western United States on Friday is a one-in-500-year event and almost certainly the result of human-caused climate change, experts say.

The heat has been toppling records this week and is set to continue into the weekend across western cities while expanding eastward.

Four locations in the desert area near the California-Arizona border registered 44.4 degrees Celsius on Friday, a US national record for March. The readings were recorded near Yuma and Martinez Lake in Arizona, and around Winterhaven and Ogilby in California.

Read: Intense heatwave grips US, triggering record-breaking temperatures

Already, 65 cities have recorded new March highs, ranging from Arizona and California to Idaho, Weather.com reported.

Death Valley reached 40°C on Thursday, while typically cool and foggy San Francisco tied its historic March record at 29°C. In Colorado, skiers were seen hitting the slopes shirtless.

The National Weather Service issued extreme heat warnings on Friday for much of the southwest, from Los Angeles and coastal southern California to Las Vegas. Authorities also warned against leaving children or pets in cars. The unusually intense heat, arriving as winter ends, has alarmed climate experts.

“This heat wave would be virtually impossible for the time of year in a world without human-induced climate change,” the World Weather Attribution network said in a report.

“These findings leave no room for doubt. Climate change is pushing weather into extremes that would have been unthinkable in a pre-industrial world,” said Friederike Otto, a professor at Imperial College London.

The scientists described the event as so rare that, despite rising global temperatures, such extremes would be expected only once every 500 years.

“In the US West, the seasons people and nature relied on for centuries are disappearing, putting many — including outdoor workers and those without air conditioning — at risk,” she said. “The threat isn’t distant — it is here, it is worsening, and policy must catch up with reality.”

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‘This is global warming’

Scientists say there is overwhelming evidence that today’s heat waves are a clear marker of global warming, driven primarily by the burning of fossil fuels.

With the northern hemisphere exiting winter and entering astronomical spring on Friday, the soaring temperatures are already affecting wildlife in the West. Many plants and trees are blooming early, with vegetation growing rapidly after heavy rains in December and January.

“This is very unusual. We’re still in winter,” she said.

“But this is global warming. The East Coast is seeing tornadoes and snow, and here we are, sizzling.”

Terry Salas, a resident in Los Angeles, said recent weather patterns across the United States had been unusual.

“We’re having summer temperatures that we never, ever had in March.”