The answer to all of these questions is yes.

[Read more about Smokey Bear and the question of personal responsibility in preventing wildfires.]

A fire needs a spark. If PG&E’s wires provide that, then the company is responsible, just as I would be if I started a fire with a tossed cigarette or an unattended campfire. Californians are right to try to hold PG&E accountable, and the evidence suggests that it has been poorly managed, deferring crucial maintenance for years.

At the same time, the fire wouldn’t spread so far and be so catastrophic if the weather weren’t right for it. And while the proximate causes of the National Weather Service’s fire weather watches and red flag warnings lie in the more or less random fluctuations of day-to-day weather, there is compelling evidence that global warming has increased the risk substantially. Heat dries out what scientists who study the problem clinically refer to as “fuel” — that is, trees and shrubs and such — so that they burn more quickly and easily.

[How PG&E ignored fire risks in pursuit of profit.]

Then again, tree rings show that there have been droughts even worse than those in the past century, and that fire has been a part of the natural history of California and the western United States for millenniums. So human greenhouse gas emissions are by no means solely to blame.

But they make the problem worse than it would otherwise be, since the natural climate variability is already a given, in exactly the same way that bad habits, like smoking, increase the risks of diseases that one would already stand some risk of getting due to bad luck alone.