Over the last few years we’ve heard story after story about massive wildfires in the western USA which threatened thousands of homes and lives and cost people billions of dollars. California seemed especially hard hit, especially last year. For me, the story of a great-grandmother dying in a fire with her two great-grandsons in her arms, is a sadness too great to bear.
So I’ve been glad that this year, I haven’t noticed such news stories about truly horrific gargantuan western wildfires. Until … now. In California.
Why, one wonders, has the situation gotten out of hand? There are many factors, but one thing that we know, without doubt, affects wildfire is the climate. Ask firefighters. One of the faces of climate change, is a change of the average weather — and weather affects wildfire profoundly. The hotter and dryer it is, the more likely it becomes for fires that do spark — and fires will spark — to explode in size and fury with such speed we have no hope of keeping up. Ask firefighters.
The climate is changing, and in SoCal this shows most clearly as a rise in average temperature. Here’s what it’s been up to during the summer months (June, July, and August) since 1895 in the “South Coast Drainage” climate division of California:
The temperature increase is as plain as day. Higher temperature makes wildfire worse. Ask firefighters.
Another obvious weather effect is precipitation. However, we haven’t really seen any trend in precipitation amounts during the southern California summer; there are hints, but nothing “statistically significant.” What this means is that we can expect (for the time being at least) the same behavior we’ve seen in the past. We’ll get wet summers in southern California, we’ll get dry ones. The dry ones will be extra-vulnerable to wildfire, and they’ll come at unpredictable but unavoidable times. And when they do, temperatures will be hotter.
The combination of dry and hot is getting far more frequent, because these days a “hot” summer is a sure thing. These days, a “very hot” summer is a sure thing. That’s making wildfire worse, not just in SoCal but all over the western USA. Ask firefighers.
Some people try very hard to persuade you that fighting climate change won’t help with the wildfire problem. Some even try to convince you that climate change has nothing to do with it. It’s all about the fact that there are more people at risk, more property in vulnerable areas, so of course there’s more damage. It’s all about how we’ve mismanaged forest fire suppression, making things more dangerous. Climate change, they argue, is either too small an effect to be relevant, or none at all.
I sugest they talk to some firefighers.
Those risk factors are real. They even give us valuable clues about how to mitigate the damage. If we have less development in fire-prone areas, we’ll suffer less. If we manage fires with a view toward not just suppressing fire, but suppressing fire conditions, we can help significantly. We really should pay attention to those things, and act on that knowledge.
But if you don’t believe that climate change is a significant factor, not just a trivial one, then you need to talk to firefighters. A lot of them.
The American southwest is hardly the only place on earth suffering such conflagrations. Last year we saw them not just explode, but turn deadly all over the northern hemisphere, including places you wouldn’t expect like the Arctic circle. The southern hemisphere hasn’t gone unscorched either; they’re feeling the heat in Australia and New Zealand too. Why? In Australia, a nation that’s already inherently dry is getting hotter too. Here’s what summertime average temperature has been doing in the Australian state of New South Wales (hard hit by wildire, which they call “bushfire,” right now; Australian states are big, like Texas) during the summer season (summer in the southern hemisphere being December, January, and February):
As hot as it is already in California, in Australia, in most of the world, because of climate change, it will get hotter. That means wildfire is going to get worse. Really. It’s already bad, it’s already serious. Imagine that as much as it’s costing us now, it gets twice as bad. Imagine it gets five times as bad. Or more. That’s what we’re headed for, because as temperatures continue to rise it will transform the ecosystem, and in southern California and Australia and other places, much of that transformation will revolve around wildfire. Hotter makes wildfire worse, especially encouraging large wildfires.
The important question is: how much worse will it get? That’s where fighting climate change comes in: how much worse it gets depends, significantly, on how much hotter it gets. I don’t know how much worse it will get even if we do shoulder the burden of option #1: get serious about fighting climate change, or if we stick with option #2: do nothing (business as usual). But this much I do know: option #2 is a lot worse than option #1. A lot.
We can pay now, or we can pay later. Now is expensive as hell. Later is hell.
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Open Mind 
As someone who lives in South Australia, often referred to as the driest state in the driest inhabited continent, I can attest to your comments. We’ve had our share of bad bushfires, as has Victoria and other states, most recently Queensland and NSW (as you say). I’m sure our firefighters (many of who are volunteers in the country) would give a similar story to their US counterparts; about 200 Australian and NZ firefighters went to help with Californian wildfires this time last year.
[Response: We say a sincere thanks, and we are proud of their courage and service.]
https://static.pressfrom.info/upload/images/real/2018/11/13/california-s-camp-fire-burned-hot-enough-to-melt-aluminum-in-cars__611011_.jpg?content=1
Maybe even scarier:
http://bravenewclimate.proboards.com/thread/160/ecological-impacts?page=1#post-6044
To be fair to that SJ Mercury News article, it is true that if you look only at the wetness of the previous winter, high wetness does delay onset of fires, because even the resulting extra fuel is wetter, and the soil is wetter. That extra fuel becomes problematic when it dries enough to outweigh the safety from the extra moisture. High VPD increases the rate of drying. So there is an interaction of previous winter wetness with summer and fall VPD.
Also, if there happens to be little fire in a summer-fall season following a wet winter, that extra fuel remains available in the following fire season.
Perhaps, Tamino, you might write a journal article on those two aspects, unless Williams or others already covered them.
[Response: They do a pretty good job of it. The paper by Williams et al. is also quite well written; I can’t recommend it strongly enough.]
I live in the Santa Cruz Mountains in California, in the woods and so at high risk of fire. Until the surge in fires over the past month or so, this summer folks were relieved at the lack of fires, compared to the recent past years. The explanation was remnant moisture in vegetation and soil from the wet winters—I think mention was made of remnant moisture from even two years ago! So the drying can take quite a while, complicating causal analysis of fires.