Worst heat in years threatens to take down California's grid

[SACRAMENTO] One of the most extreme heat waves in generations is smothering California this week and pushing the region's power grid to the brink of collapse.

In the past 72 hours, the state has declared two grid emergencies and instituted the first rolling blackouts since the 2001 energy crisis to protect a system strained by people blasting air conditioners and power plants tripping offline. The region's electricity system operator has warned of more rotating outages through Wednesday with temperatures forecast to reach as high as 44 degrees Celsius in some parts of the state.

By 7.30 am local time it was already 26 degrees Celsius in Sacramento. With temperatures climbing, demand for power in the state is expected to reach more than 49,700 megawatts Monday afternoon, just shy of the all-time record set in 2006.

Since Friday, millions of Californians have been abruptly plunged into darkness with little notice as utilities work to keep the state's grid from collapsing. With Covid-19 still spreading, the powerless have faced a difficult choice between enduring the heat at home and seeking relief elsewhere in a state that's reported more infections than any other.

These blackouts are hitting less than a year after California's utilities deliberately cut power to millions to keep their electrical lines from sparking fires during unusually strong windstorms, all extreme weather events made more frequent by climate change.

Monday and Tuesday "will be quite hot, and there will be a number of records again," said David Roth, a senior branch forecaster with the US Weather Prediction Centre. "It is pretty much the whole West."

The relentless heat is starting to take a physical toll on California's power system. Transformers - the metal cylinders sitting atop power poles - can malfunction and catch fire if they don't cool off at night. And temperatures in some parts of Southern California are expected to remain in the low 20's overnight. During a deadly, 10-day heatwave in 2006, the state's utilities lost more than 1,500 of these devices, with each knocking out service to one neighbourhood in the process.

The heat wave gripping the West Coast stems from a stubborn, high-pressure system that has parked itself across the Great Basin spanning Nevada and other western states. It essentially acts as a lid trapping hot air, and there aren't any indications it's going to budge soon.

Such phenomenons, sometimes called heat domes, are getting worse because the Earth's climate is changing. As the planet warms, the contrast between the heat at the equator and the cold at the pole decreases. That saps the strength of the jet stream, which otherwise would be able to shove the ridges out of the way. It explains in part why extreme heat has blanketed regions around the world in recent weeks.

BLOOMBERG