Jul 9, 2018

Go deeper: "Human fingerprint" on California's blistering heat wave

The remains of a destroyed car stand infront of a destroyed home in the aftermath of the Holiday Fire on July 7, 2018 in Goleta, California. Credit: Mario Tama/Getty Images

Southern California's intense heat wave, which has shattered dozens of temperature milestones, including all-time records, is exactly the kind of event that is becoming more likely and severe due to global warming, scientists told Axios.

Why this matters: The heat wave has sparked destructive wildfires and threatened public health for millions of Californians, and is a stark reminder that even a small amount of global warming can push climate extremes into new and far more dangerous territory.

By the numbers

Consider some of the records that have been set so far during what now ranks as one of Southern California's all-time hottest heat waves.

  • 82° Fahrenheit: Hottest all-time overnight low temperature on record for any month in Burbank, California.
  • 79°F: Hottest overnight low temperature on record for the month of July in L.A. on July 7.
  • 111° F: Hottest daytime high temperature ever recorded at the UCLA weather station in Los Angeles, set on July 6. This beat the old record of 109°F, set in 1939.
  • 114°F: Hottest all-time temperature on record at Burbank Airport, recorded on July 6.
  • 120° F: Highest temperature — set in Chino on July 6 — ever recorded by any automated weather station in the valleys or coastal areas around Orange, Riverside, San Bernardino and San Diego Counties.

The big picture: This event occurred months earlier than usual, and still set all-time records. California's hottest time of year tends to be in the early fall, when dry, down-sloping winds, known as the Santa Ana, blow from east to west, compressing and heating up the air as it flows into Los Angeles and San Diego.

Computer model simulation showing extremely hot temperatures in southern California on July 6, 2018.
What they're saying

Climate scientists told Axios that global climate change is a significant factor behind the heat event, even though it's not the proximate cause.

  • Stanford University climate scientist Noah Diffenbaugh has published studies showing how a relatively small shift in the global average surface temperature of just 1° Celsius, or about 1.8°F, in the past century has dramatically upped the odds of severe heat events.
“When we look around the world at record hot events we find there’s already a human fingerprint at 80% of the events where we have observational records.”
— Diffenbaugh
  • Daniel Swain, a climate scientist at UCLA, noted that there has not yet been a formal study on the connection between this heat wave and climate change, since that could take a few weeks to complete. Such studies are known as "climate attribution" research. However, the climate change link to this event is already evident, he said.
“The reality is when it comes to heatwaves now there’s almost always a human fingerprint. One of the clearest consequences of global warming is more heat, higher temperatures.”
— Daniel Swain, climate scientist at UCLA
The bottom line

Michael Wehner of Lawrence Berkeley National Laboratory, who is working to conduct extreme event attribution studies in advance of an event, told Axios via email, that "[i]n probabilistic terms, climate change increased the chances of the heat wave by about 20 to 50 times," adding that there is at least a 99% likelihood that human-induced climate change "increased the severity of this heat wave."

Go deeper

In photos: Authorities issue warning as Americans venture out for Memorial Day weekend

Venice Beach in Los Angeles on May 24. Photo: David McNew/Getty Images

Authorities urged Americans to maintain social distancing and wear masks against the coronavirus amid reports of packed beaches and bars during the Memorial Day weekend.

Driving the news: Law enforcement stepped up beach patrols, authorities on Florida's Gulf Coast closed parking lots because they were full and there were crowded scenes at Lake of the Ozarks bars in Missouri, per AP, which reports a shooting injured several people at a packed Daytona Beach in Florida.

Coronavirus dashboard

Illustration: Aïda Amer/Axios

  1. Global: Total confirmed cases as of 9:30 p.m. ET: 5,405,029 — Total deaths: 344,997 — Total recoveries — 2,168,408Map.
  2. U.S.: Total confirmed cases as of 9:30 p.m. ET: 1,642,021 — Total deaths: 97,698 — Total recoveries: 366,736 — Total tested: 14,163,195Map.
  3. World: White House announces travel restrictions on Brazil, coronavirus hotspot in Southern Hemisphere Over 100 coronavirus cases in Germany tied to single day of church services — Boris Johnson backs top aide amid reports that he broke U.K. lockdown while exhibiting symptoms.
  4. Public health: Officials are urging Americans to wear masks headed into Memorial Day weekend Report finds "little evidence" coronavirus under control in most statesHurricanes, wildfires, the flu could strain COVID-19 response
  5. Economy: White House economic adviser Kevin Hassett says it's possible the unemployment rate could still be in double digits by November's election — Public employees brace for layoffs.
  6. Federal government: Trump attacks a Columbia University study that suggests earlier lockdown could have saved 36,000 American lives.
  7. What should I do? Hydroxychloroquine questions answeredTraveling, asthma, dishes, disinfectants and being contagiousMasks, lending books and self-isolatingExercise, laundry, what counts as soap — Pets, moving and personal healthAnswers about the virus from Axios expertsWhat to know about social distancingHow to minimize your risk.
  8. Other resources: CDC on how to avoid the virus, what to do if you get it, the right mask to wear.

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Updated 1 hour ago - Politics & Policy

Republicans sue California over mail-out ballot plan

California Gov. Gavin Newsom during a February news conference in Sacramento, California. Photo: Justin Sullivan/Getty Images

President Trump accused Democrats of trying "Rig" November's general election as Republican groups filed a lawsuit against California Sunday in an attempt to stop Gov. Gavin Newsom (D) from mailing ballots to all registered voters.

Driving the news: Newsom signed an executive order this month in response to the coronavirus pandemic ensuring that all registered voters in the state receive a mail-in ballot.