San Francisco Frontiers - Record-breaking heat wave grips western US

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

One spot in the desert area at Martinez Lake, Arizona registered 43C -- a US national record for March. Already, 65 cities have seen new March highs, ranging from Arizona and California to Idaho, weather.com reported.

Death Valley on Thursday scorched in 40C degrees while the often cool and foggy San Francisco tied its historic March record at 29C degrees, and skiers in Colorado were hitting the slopes shirtless.

The National Weather Service issued extreme heat warnings Friday for much of the southwest, ranging from Los Angeles and coastal southern California to the desert gambling capital of Las Vegas.

Warnings were issued against leaving children or pets in cars.

The phenomenal heat when winter is only just ending alarmed climate watchers, who saw evidence of dire change.

"This heatwave would be virtually impossible for the time of year in a world without human-induced climate change," World Weather Attribution scientists said in a report.

They called the event so rare that despite overall rising temperatures something this serious is only "expected to occur about once every 500 years."

"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 one of the study's authors, Friederike Otto, a climate science professor at Imperial College London.

"In the US West, the seasons that people and nature were used to for centuries are disappearing, putting many, including outdoor workers and those without air conditioning in danger," she said. "The threat isn't distant -- it is here, it is worsening, and our policy must catch up with reality."

- Global warming -

Scientists say there is overwhelming evidence that today's heat waves are a clear marker of global warming, a process driven chiefly by humanity's unchecked burning of fossil fuels.

With the northern hemisphere only exiting official winter on Friday -- the first day of astronomical spring -- the soaring temperatures were wreaking havoc on wildlife in the West.

Many plants and trees are already blooming, and vegetation is growing at a fantastic clip, fuelled by heavy rains in December and January.

Terry Salas, who was out and about in Los Angeles on Thursday, told AFP the climate across the United States in recent weeks had been crazy.

"This is very unusual. We're still in winter," she said. "But this is global warming. The East Coast is just tornadoes and snow, and here we are, we're sizzling."

"We're having summer temperatures that we never, ever had in March."

H.Reyes--SFF