by Wen Tsui
SACRAMENTO, United States, March 21 (Xinhua) -- A record-breaking heat wave swept across the western United States this week, shattering March temperature records in dozens of cities.
A corporate public relations professional who flew in from Toronto, Canada, described the temperature shift as a "physical shock," with her home city at around minus 10 degrees Celsius at departure and San Jose near 30 degrees upon arrival -- a staggering 40-degree swing.
The U.S. National Weather Service (NWS) Bay Area office said a downtown San Jose climate station reached 31.1 degrees Celsius, breaking the previous March 20 record of 25.6 degrees Celsius set in 2004.
By Friday, more than 550 daily high-temperature records had been set across the western United States since March 11, with at least 65 locations logging all-time March highs, according to media reports, spanning Arizona, California and Idaho.
The highest reading reported by the NWS came from a desert area near Martinez Lake, Arizona, where temperatures reached 43.3 degrees Celsius on Thursday, surpassing the previous U.S. March record of 42.2 degrees Celsius set in Texas in 1954.
Further reports showed additional extremes in Arizona and Southern California. In Phoenix, Arizona, temperatures rose to 40.6 degrees Celsius, matching the city's all-time April record -- in March.
The World Weather Attribution group said in a rapid, non-peer-reviewed analysis that the event "would have been virtually impossible without human-induced climate change," estimating fossil fuels added 2.6-4 degrees Celsius to observed temperatures and placing the event's return period at about 500 years under current conditions.
"These findings leave no room for doubt," said Friederike Otto, a climate science professor at Imperial College London and co-author of the analysis. "Climate change is pushing weather into extremes that would have been unthinkable in a pre-industrial world."
Daniel Swain, a climate scientist with the University of California Agriculture and Natural Resources, said the atmospheric ridge driving the heat wave was the strongest ever observed over the southwestern United States in March, linking recent extremes -- including heat and wildfires -- to climate change. He warned that April 1 snowpack levels across western watersheds could fall to record lows, threatening summer water supplies.
Russ Schumacher, Colorado's state climatologist and a professor at Colorado State University, told the San Francisco Chronicle there is "no analog in March - not even close." ■
