Yes, Human-Caused Climate Change Contributed to the Burning of Los Angeles

The Los Angeles wildfires have destroyed over 1,000 buildings, forced thousands from their homes and left at least five dead so far. The Palisades fire destroyed many historic structures, including the home of legendary comedian and actor Will Rogers. Reading some of his quotes, I conclude that the sorry episode would not have surprised him in the least. People who know me know that I have a California dimension — my father was stationed there on a couple of occasions in the Army, and I earned a degree at UCLA. I’m devastated. Some of my friends had to flee their homes.

As the experts quoted by Matt McGrath at the BBC point out, climate change certainly played a role in the destruction of Pacific Palisades and Altadena in Los Angeles, even if its precise effect has yet to be calculated.

He cites Stefan Doerr, the director of the Centre for Wildfire Research at Swansea University, as saying, “While fires are common and natural in this region, California has seen some of the most significant increases in the length and extremity of the fire weather season globally in recent decades, driven largely by climate change.”

Doerr goes on to caution that the precise contribution of human-caused climate change to the conflagration has yet to be estimated. The question is not not whether our carbon dioxide and methane emissions turbocharged the wildfires, but how much they did. Was it by 10% or 30%? There is some indication it could have been by 40%.

Climate is long-term weather patterns. Weather is a one-off. A two-day downpour can be weather. A long-term increase in rainfall over previous averages would be climate change.

The ways in which weather contributed to the Los Angeles catastrophe are easier to specify. California had a 20-year drought that ended two years ago. The plentiful rainfall since then caused a lot of shrubs and greenery to spring up. Then, the past several months have been extremely dry. The December rains did not come. Usually there would have been four inches by early January, but it was less than an inch. That water would have tamped down the fire risk. Then the Santa Ana winds blew west through the mountains. They were unusually strong and hot, and they hit places they usually missed, drying everything out further.

But why has this year been so dry, creating abundant “fuel” for the wildfire demons?

In 2021, Daniel Swain, a climate scientist at UCLA, published a study pointed to the burning of fossil fuels, putting more carbon dioxide into the atmosphere, as a cause of more frequent and longer dry autumns. Extending the dry season increases the overlap of the Santa Ana winds in fall and winter. That is a recipe for disaster. Swain cites another study showing that between 1960 and 2019, November has gotten consistently drier. But since there is a clear pattern of desiccation in the 11th month over decades, it isn’t about weather; it’s about climate.

Worse, Swain thinks we may see more of this deadly overlap as humans continue to heat the planet.

He also cites studies showing that winter rains may be concentrated later in the year. You could have some showers in October in the old days, and November could be wet. Increasingly, those months are dry, and rains fall December through February, often concentrated in January and February.

I’ve long noticed how much it rains in the Raymond Chandler mysteries set in Los Angeles. Except for February, I don’t remember it being that rainy, cool and miserable in L.A. At first, I thought it was because Chandler spent some of his formative years in Britain and he was importing his weather imagery to southern California. But after reading Swain’s report, I wonder if the rain was just spread out more in the 1930s and ’40s, and whether there used to be more of it.

So how much have humans ramped up the dangers of climate change? A 2022 paper led by Linnia R. Hawkins, then at Oregon State University, used a computer study to compare the current likelihood of autumn wildfires in California and Oregon to what it might be without human-caused climate change. They found a 40% increase in the likelihood:

Present-day anthropogenic climate change has … increased the likelihood of extreme fire weather indices by 40% in areas where recent autumn wind-driven fires have occurred in northern California and Oregon. The increase was primarily through increased autumn fuel aridity and warmer temperatures during dry wind events. These findings illustrate that anthropogenic climate change is exacerbating autumn fire weather extremes that contribute to high-impact catastrophic fires in populated regions of the western U.S.

The authors, however, cite literature that does not find a strong climate change effect for changes in the Santa Ana winds. It is possible that those 100-mile-an-hour gales hitting places they usually don’t, such as Altadena and Pasadena, were just weather. But combined with the extra heat and aridity in the fall being driving by climate change, they proved deadly.