California Fire Updates: Getty Fire Forces Evacuations in West Los Angeles as Kincade Fire Burns

In the case of the increasingly frequent wildfire disasters in California, I argued the other day that they have multiple causes: poor maintenance by PG&E, expanded human settlement at the margins of fire-prone woodlands, and global warming. But I don’t think any of them explains either the suddenness or the persistence of the change that Californians have experienced in the last three years.

When it comes to the weather, and the climate, my views here are strongly informed by discussions with my colleague Park Williams, an expert on wildfire and climate whose research is directly relevant. That research shows that the area burned by fires each year in the summer months has increased drastically, and this is consistent with the influence expected from global warming.

But, as explained by Dr. Williams in his recent research article, and in The Times on Friday, the headline-making fires of the last three years have all occurred in fall. In that season, temperature has a role, but other factors are likely to be more important — first and foremost, the dry Diablo and Santa Ana winds.

Those are mainly fall and winter phenomena, and clearly critical factors in the recent and current fires. But these winds are actually projected to occur less frequently as the climate warms (with no clear trend yet apparent in the observations). So the fires may be attributable to weather, but the most critical aspect of the weather isn’t directly attributable to human activity — nor, as far as I can tell, to any other, identifiable, larger cause.

So what is going on?

My guess is that the best scientific answer goes something like this. The sparking might have gotten worse over time. But more important, in the last three years, it has encountered the hot, dry downslope winds markedly more often. And global warming is probably making those winds a little hotter, but the wind events themselves, the most important proximate causes, may well be only explainable, ultimately, as “natural variability.” That means they are inherently unpredictable. Bad luck, in other words. If this is true, it would suggest a decent chance that next year shouldn’t be as bad.

Or maybe the causes are in principle knowable, but current science just doesn’t know them. Maybe climate change is proceeding more rapidly and dangerously than we understand. But it’s good to understand what the limits of our knowledge are. That should keep us humble about our place on the earth.

Reporting was contributed by Nicholas Bogel-Burroughs, Ivan Penn, Jacey Fortin and Lauren Hepler.