Climate-related 'one-two punch' seen driving Los Angeles wildfires

By Andrew Hay

(Reuters) - Wildfires around Los Angeles have burned rapidly in the past week after vegetation growth and record heat blamed on climate change, and Southern California blazes could get worse once seasonal winds start, according to climate scientists.

Three blazes in mountains around the second-largest U.S. city have destroyed more than 230 houses and other structures, forcing tens of thousands of people to evacuate suburbs and towns since Sept. 5.

The Los Angeles mountains are ripe for fire after consecutive wet winters created an abundance of grass and brush that dried out during recent triple-digit heat.

"That one-two punch, that sequence, means you grow all this extra potential fuel for fires and then you dry it out to extreme levels," said Daniel Swain, a UCLA climate scientist whose research suggests California's rising temperatures create wetter winters.

Gusty winds have sent wildfires largely eastward, away from suburbs and towns. Santa Ana winds that typically start this month blow westward toward densely populated areas.

"As long as the Santa Ana winds are blowing, we run the risk of big fires until we really get our first rains," said Alex Hall, a professor in UCLA's Department of Atmospheric and Oceanic Sciences.

Hall said authorities and residents need to rethink any activities that cause human-made sparks and flames responsible for nearly all fires.

The Airport Fire in the Santa Ana Mountains 45 miles (72 km)southeast of Los Angeles began with a spark from a digger moving boulders to block vehicle access to a wilderness area.

The 24,000-acre (9,700-hectare) blaze, now 31 percent contained, has destroyed 160 houses and other structures.

Fires often are a natural occurrence in the mountains. Their suppression over the past century has led to a build up of fallen trees, scrub and other fuel.

The Bridge Fire about 35 miles (56 km) northeast of downtown last week grew tenfold to 49,000 acres (20,000 hectares) in 24 hours as it tore over fuel-packed mountains that had not burned in at least two decades. That blaze is now at 55,000 acres (22,000 hectares) and 37 percent contained.

California wildfires have so far burned nearly four times as much land in 2024 as at the same time during last year's benign fire season, according to Department of Forestry and Fire Protection or CAL FIRE data. Burned acreage this year is slightly above the five-year average.

Nine of the state's 10 largest wildfires on record have been in the past decade.

Nationally, wildfires have scorched 7.3 million acres (2.95 million hectares) this year, more than the full-year average of around 7 million acres (2.83 million hectares) over the past decade, according to National Interagency Fire Center data.

(Reporting by Andrew Hay; Editing by Will Dunham)