The Washington PostDemocracy Dies in Darkness

Record heat put thousands of Californians in the dark Friday. Scientists predicted this from climate change.

A surfer attempts to beat the heat in San Diego on Sunday. (Jim Grant via Twitter)

Temperatures shot up over 110 degrees in Southern California on Friday, obliterating all kinds of long-standing heat records, and the lights went out for tens of thousands of customers. Californians were powerless, without air conditioning, in the hottest weather many had ever experienced.

Climate scientists have known this was coming, and it may only be the beginning.

“We studied this a long time ago . . . now our projections are becoming reality,” tweeted Katharine Hayhoe, a climate scientist at Texas Tech University.

In 2006, Hayhoe and colleagues published the study “Climate, Extreme Heat, and Electricity Demand in California” in the Journal of Applied Meteorology and Climatology.

“Over the twenty-first century, the frequency of extreme-heat events for major cities in heavily air-conditioned California is projected to increase rapidly,” the study said. It warned that as temperatures soared, electricity demand would exceed supply.

Friday’s weather and the resulting blackouts illustrated their point.

“Skyrocketing electricity demand due to Friday’s triple-digit temperatures triggered power outages around Los Angeles that are still affecting about 34,500 residences and businesses,” the Los Angeles Times reported Saturday afternoon. “Peak energy demand climbed to 6,256 megawatts on Friday, knocking down the previous July record of 6,165 megawatts set in 2006,” which happened to be the same year the Hayhoe study was published.

Hot air masses are more intense

The blistering temperatures Friday, more than the power grid could handle, occurred against a backdrop of more-intense hot-air masses due to climate change.

Multiple analyses have shown that the strength of heat domes, the bulging zones of high pressure that are the source of extremely high temperatures, has trended upward in recent decades.

An analysis conducted by meteorologists at the National Weather Service in State College, Pa., and Pennsylvania State University found an increase in the intensity of heat domes over the entire Northern Hemisphere during the summer months from 1979 to 2010.

The intensity of heat domes is evaluated using a measure known as “geopotential height,” which is the height in the atmosphere at which 500 millibars of pressure occur. The higher this pressure level is, the hotter it is, because hot air is less dense than cold air and fills more space. The most intense heat domes, which are extraordinarily rare, feature geopotential heights exceeding 6,000 meters at their core.

Friday’s heat dome exceeded the 6,000-meter geopotential height threshold in several locations in the Western United States and was nearly that high (5,940 meters or higher, as shown within the red outline in the image below) over a sprawling area from Southern California to southern New England.

It was this same heat dome that led to the hottest weather ever recorded in Denver and Montreal, where dozens of heat-related deaths have occurred.

Red-hot planet: All-time heat records have been set all over the world during the past week

Data shows that hot domes this extreme are becoming more common. Last summer, Ryan Maue, a meteorologist for,  examined data back to 1958 and found almost all of the heat domes exceeding this 6,000-meter threshold in the Western United States have occurred since 1983 — with the overwhelming majority forming since 1990.

Because of the warming climate, “I’d surmise that the [6,000-meter] threshold — while an arbitrary big round number — is now more easily exceeded,” Maue told the Capital Weather Gang.

‘Jaw dropping’ records set

The massive heat dome spurred a remarkable slate of high-temperature records in Southern California. Most records for July 6 were obliterated, and quite of few of the highest temperatures were the highest for the month of July or any month of the year, known as “all-time” records.

Friday’s high of 120 degrees in Chino was the highest ever recorded by any automated weather station in the region around San Diego. “This one, to me, was absolutely jaw dropping,” tweeted Matt Lanza, a meteorologist based in Houston.

The weather station at the University of California at Los Angeles, which has kept measurements since 1933, posted a high of 111 degrees, destroying the previous July 6 record of 89 and edging past its all-time record of 109 set Sept. 20, 1939. Other locations that set all-time highs include:

  • Hollywood Burbank Airport, 114 degrees
  • Van Nuys Airport, 117 degrees
  • Ramona, 117 degrees
  • Santa Ana, 114 degrees
  • Riverside, 118 degrees (tying record from 1925)

All-time high temperature records set throughout Southern California, including Los Angeles

Not only were temperatures historically hot during the day, but they also failed to cool off much at night — placing added stress on the power grid. Downtown Los Angeles cooled to only 79 degrees Saturday, its highest minimum temperature on record for the month of July.

Only the beginning?

If projections are correct, heat waves will become worse in the coming decades, further taxing California’s energy supply. Hayhoe’s 2006 study concluded a “potential for electricity deficits as high as 17 percent” later this century.

Of course, the Catch-22 is that if cities increase electricity capacity to adapt to a changing climate using fossil-fuel-based energy sources, greenhouse-gas emissions increase, which warm the climate even more.

Demand for cooling is expected to explode in the developing world, where air conditioning is scarce. In its May story “The World Wants Air-Conditioning. That Could Warm the World,” the New York Times reported that the number of air conditioners worldwide is projected to increase more than threefold by 2050.

“Air conditioning saves lives from heat waves,” Jonathan Patz, who directs the University of Wisconsin’s Global Health Institute, told Earther. “But if the electricity to run air conditioners requires coal-fired power plants, then we have a problem.”