I'm not sure about the NUMBER of fires. That might be hard to count. If five small fires emerge and are put out, there are five fires. If five fires emerge, join into one configuration, and wipe out a handful of mountain villages in the Rockies, that's one fire. It might be better to look at acreage burned per year.
My friend John Abraham has used the data supplied by National Interagency Fire Center to make a graph of acreage burned per year since 1960. The graph is a 10-year running mean of millions of acres burned in the US.
Here is the graph:
The annual rate of acreage burned in forest fires in the US seems to be increasing, presumably related to global warming.
Looks like a bit of an upswing.
For comparison, here is a section of a graph from this source showing temperatures (blue line) in the US Lower 48 for the roughly equivalent time period:
Tamino's done his usual statistical wizardry on these wildfire numbers at his blog as well.
I posted the following at Tamino's site....but I'm putting a copy here for your readers...
Tamino shows a statistically significant trend, but you don’t even attempt to attribute it to warming. Wildfire is one of those areas where multiple human causes are at play, including changing forest management practices. You might want to look at the excellent paper by Littell et al, 2007 “Climate and wildﬁre area burned in western U.S. ecoprovinces, 1916–2003″ [google it] for a longer term view. It turns out there were large areas burned in the 1920′s — as large as in the 2000′s. A clear dependence on climate emerges from their analysis, but the importance of warm temperatures as a determinant of acres burned differs from region to region.
Thanks for that link.
Surely there are multiple causes of dramatically increased fires. For earlier periods, I wonder about bad lumbering practices in the west in some areas (that may not have been a factor, just wondering). Certainly, Minnesota burned down a couple of times because of that.
Warming leads to tree death and increased parasite activity, which leads to tree and tree tissue death, all of which lead to fire risk. But ozone pollution can also lead to increased tree tissue death. But the effects of ozone are enhanced by warming. So even without drought, there is a complex of causes in addition to bad management that involve climate change and other factors that are at play.
Then we add drought and that seems to be a major factor.
A tree is at the end of a large number of complex interconnected causal chains!
And we've not even talked about how fires start...
Many years ago, I read an article in one of the hunting and fishing magazines about roadside fires. The article said that the majority of roadside fires were the result of focusing the sun by pieces of broken glass rather than carelessly tossed cigarettes. I never saw anything more about it. If the article is correct, I think the advent of plastics should have cut down on the amount of roadside broken glass.
A couple of years ago, we drove from Dallas to Austin on I 35. This was soon after the big fires around Bastrop. Every four or five miles, we would see where there had been a burn confined to the right of way. I only saw one which had crossed a fence and gotten a little bit of pasture. There was a helicopter in the distance, dropping water. i never knew what had gone on there. Were several firetrucks driving up and down the road putting out little fires, or what?
Ok, well, where I live, you can get a job as a volunteer fire fighter available to fight brush fires. It's volunteer but you get something like 50 bucks every time you are called out on a crew. A couple of years ago, a guy who had lost his business (because he got caught defrauding people or something) had one of these positions. That year there were a LOT of roadside fires, including one that burned up much of the Conrad Averly Wildlife Refuge.
One day that guy was caught driving along the road in a marshy area (the marshes are low in the early spring so they are tinder boxes) shooting fireworks into the dry brush, staring one fire after another. I assume his plan was to pick up an extra fifty bucks a couple of times a week.
After he was arrested, a two or three year period of an unusual number of roadside fires came to an end. We've not had a significant brush fire in the area since then, save one last fafll, and even that one was not very big.
Jim @3: In some places controlled burns are a part of wildfire management. The idea is that if you use up the available fuel in a small fire, it won't be there to contribute to a larger fire. (Also, some plant species in the prairies and forests of western North America have evolved to depend on occasional wildfires to aid their reproductive cycles.) DON'T TRY THIS AT HOME, KIDS! If the humidity is too low or winds are too strong, these so-called controlled burns can go out of control. At least one major wildfire, in the Los Alamos area circa 2000, started when a controlled burn went out of control.
I have no idea whether this is what they were doing in Texas, but it fits all the facts known to me, including the fact that one or two of these fires did get out of control.
We worked at prairie restoration on a couple of acres on campus, near St. Louis. We had a yearly controlled burn, with permit, and firetrucks standing by. It was quite spectacular.
The roadside burns mentioned above were in in dry roadside grass, mostly Bermuda and red fescue.
For several months, I got to help with the burning program at a major national park in Africa. Lighting the savanna on fire was fun.
This trend was discussed during a session at the fall 2012 AGU meeting in San Francisco:
Thanks I'll give that a whole blog post of its own!