Is global warming causing more, larger wildfires?

Add this to the fact that glaciers in the Western U.S. are melting at a much more excelerated pace than predicted thus causing drier conditions (California's water shortages are a testament to that) and the atmosphere is indeed ripe for these fires to be more prevalent and bigger. And the vicious cycle of it all is that these fires put into the atmopshere more CO2 thus exacerbating the situation that had a hand in starting them, and then you need water to put them out that you have less of due to less rainfall from the drier air evaporating it. I know there are yearly fires and the Santa Ana winds and all that, however, I agree that fires will be more intense as the air becomes drier and warmer. And not only are humans affected, but all species that live in those forests. Where do they go now as well? And half a million people evacuated? Something has to change.


http://www.sciencemag.org/cgi/content/full/313/5789/927

Originally published in Science Express on 6 July 2006
Science 18 August 2006:
Vol. 313. no. 5789, pp. 927 - 928
DOI: 10.1126/science.1130370
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Perspectives
CLIMATE CHANGE:
Is Global Warming Causing More, Larger Wildfires?
Steven W. Running*

On 3 April 2006, the U.S. weekly news magazine Time ran a report on global warming with the cover title "Be worried, be very worried." Similar coverage of global warming has emerged in other general-interest magazines in recent months, triggered by scientific studies that are finding evidence for adverse impacts of global warming occurring today, not merely projected for future decades. These adverse impacts--from higher probabilities of category 4 and 5 hurricanes (1, 2) to higher rates of sea-level rise (3)--are found not in some distant unpopulated region, but rather right in our own back yards.

On page 940 of this issue, Westerling et al. (4) come to a similarly discomforting conclusion for wildfires. They show that warmer temperatures appear to be increasing the duration and intensity of the wildfire season in the western United States. Since 1986, longer, warmer summers have resulted in a fourfold increase of major wildfires and a sixfold increase in the area of forest burned, compared to the period from 1970 to 1986. A similar increase in wildfire activity has been reported in Canada from 1920 to 1999 (5).

Westerling et al. used the most comprehensive data set of wildfire occurrences yet compiled for the western United States to analyze the geographic location, seasonal timing, and regional climatology of the 1166 recorded wildfires with an extent of more than 400 ha. They found that the length of the active wildfire season (when fires are actually burning) in the western United States has increased by 78 days, and that the average burn duration of large fires has increased from 7.5 to 37.1 days. Based on comparisons with climatic indices that use daily weather records to estimate land surface dryness, Westerling et al. attribute this increase in wildfire activity to an increase in spring and summer temperatures by ~0.9°C and a 1- to 4-week earlier melting of mountain snowpacks. Snow-dominated forests at elevations of ~2100 m show the greatest increase in wildfire activity.

The hydrology of the western United States is dominated by snow; 75% of annual stream-flow comes from snowpack. Snowpacks keep fire danger low in these arid forests until the spring melt period ends. Once snowmelt is complete, the forests can become combustible within 1 month because of low humidities and sparse summer rainfall. Most wildfires in the western United States are caused by lightning and human carelessness, and therefore forest dryness and hot, dry, windy weather are the necessary and increasingly common ingredients for wildfire activity for most of the summer. Snowpacks are now melting 1 to 4 weeks earlier than they did 50 years ago, and stream-flows thus also peak earlier (6, 7).

Westerling et al. found that, in the 34 years studied, years with early snowmelt (and hence a longer dry summer period) had five times as many wildfires as years with late snowmelt. High-elevation forests between 1680 and 2690 m that previously were protected from wildfire by late snowpacks are becoming increasingly vulnerable. Thus, four critical factors--earlier snowmelt, higher summer temperatures, longer fire season, and expanded vulnerable area of high-elevation forests--are combining to produce the observed increase in wildfire activity.

... contributes to the warming cycle even more.


I feel the pace quickening.

We sure have screwed ourselves.

Climate change is here and we now have to deal with it.

Their results show that large wildfire activity increased "suddenly and dramatically" in the 1980s with longer wildfire seasons and an increased number and more potent wildfires. The researchers found large fires occurred about four times more often during the 1987-2003 period than during the 1970-1986 period, and almost a seven-fold increase in the area of forested federal land burned during the latter period.

http://news.mongabay.com/2006/0706-fires.html

Longer summers also make for warmer, drier conditions. I live in the Northeast and had to put a fan on yesterday because it is still warmer than what fall should be. The weather has been every erratic here as well.

of So Cal, not necessarily. Snow melt doesn't affect these areas at all. The brush that grows there burns naturally every few years. Always has, always will. There needs to be buffers between homes and these natural landscapes.

firebreaks around homes in the hills. Unfortunately, they don't do much good in 100+ heat with hurricane-force winds like we have had recently.

Those burning embers get carried quite some distance.

About 100 years ago the Forest Service started an aggressive program to stop forest fires, remember Smokey the Bear? The forests are meant to burn to get rid of the under growth. We stopped those natural fires so the growth was left unchecked. So now you have all this fuel that explodes when lit. So Global Warming is NOT the main cause...just one of the causes.

And drier warmer conditions just make its combustion all the more possible.

global warming is probably more of a factor over all.

They have changed that doctrine in the last few years, to the "Let it burn" protcol, where only fires that threaten people and structures are aggressively faught. They now let fires in the wilderness burn themselves out.

Kicked and recommended.

Thanks, RG.

Dana Perino mentioned today in her press briefing that Al-Qeada has been planning to start wildfires. Better get Bush his 46 billion before they burn the rest of the country.

The ignorance is astounding.

I've been feeling a little depressed, surrounded by dense smoke here in LA County. I don't feel a whole lot better reading this, but you've helped resolve some of my unsettled mental state over "Why is it so much worse than usual". It's good to give a name to your pain.

I wish you all the best out there and I understand exactly what you mean. Hang in there.

... conditions become so volatile that even attempts to reduce the fuel load (via things like the "Healthy Forests" policy) will likely not make much of a difference. So there are definitely situations where climate becomes the major factor.

In conditions where the brush becomes almost explosive (low humidity, winds, etc.), there's very little one can do to stop a fire from spreading. He did his work in the boreal zone, but there are a lot of similarities to other ecosystems (and the Mediterranean-type vegetation in California is particularly flammable because of all the natural oils and other such compounds).


Twenty years ago (yikes!) I did my MSc on climate change and fire projections along the Canadian subarctic treeline (where there wasn't much interest in fire suppression, hence less of a fuel load). I've since learned that one of my major forecasts has come true in that region (increase in burned area) -- and the researchers have linked this with global warming.

What are your personal feelings regarding this? Have we indeed reached a tipping point?

Not just because of the trace-gas forcing, but we've also got a huge flood of nutrients (like nitrogen and phosphorus) that have been pouring into the environment for the past half-century). And increasing numbers of invasive species (like the water hyacinth that altered the ecosystem of Lake Victoria in only a few years).

I am hoping that this phase is "metastable" and won't snowball into feedbacks (like some of the tipping point theories suggest could happen).

Sorry, I can't remember the name of the river, but just read it is dead from algae. The people who relied on it in the millions for their water can no longer use it. It is dead. And people killed it with pollution and what they thought was "progress." And scientists now say we are seeing positive feedback loops in Greenland and the Ayles Ice Shelf in the Antarctic broke in half with oceans being reported at the saturation point regarding their ability to absorb CO2. I think we need to be seeing this as more than a phase now.

As others have mentioned , all the carbon let loose in the air and all the trees gone that absorb this will only increase global warming .

We need rain but now if we have alot then we will have mudslides and more damage .

The entire thing is a disaster .

I pray the area gets only enough rain to put out the fires and to bring relief. It is so sad to see so much natural beauty gone and lives effected as they are now.

and I never recall hearing about hurricane-force Santa Ana winds. Unfortunately this may become a new norm.