As was so succinctly put by Salon's Andrew Leonard in a post about the controversy last week: "Nuance is a bitch". Indeed, in the wake of the wildfires that ravaged large sections of Southern California, a debate that had largely remained on the sidelines - whether global warming was causing an increase in the number/intensity of fires - surged to the fore with environmental groups, scientists and pundits alike weighing in with their respective takes on the issue.
Oregon State University's Ronald Neilson, a proponent of the theory that global warming helps account for the increase in the number of wildfires, stated: "This is exactly what we've been projecting to happen, both in short-term fire forecasts for this year and the longer term patterns that can be linked to global climate change". He explained that the rise fell largely in line with his latest models, which had projected that two years of increased precipitation would create heavier biomass loads and, thus, a "tremendous fuel load" susceptible to warmer, drier weather regimes. The Los Angeles Times took a noticeably different tack, citing research done by Anthony Westerling, a climate scientist at UC Merced, to knock the suggestion that climate change was to blame for the wildfires. Westerling and his colleagues showed in a study published last year in Science that while the amount of land in Western federal forests nearly septupled between 1987 and 2003 - compared to the previous 17 years - Southern California, which has a different climate regime, experienced no increase in the number of fires as a consequence of rising temperatures.
"That is a fire-prone environment regardless of whether we are in a climate-change scenario," said Tom Wordell, a wildfire analyst at the National Interagency Fire Center - a sentiment echoed by Westerling, who noted that, "it's hot and dry much of the year" in Southern California (i.e. perfect conditions for a fire).
"In dry ecosystems where fire risks are limited by fuel availability, warmer temperatures may not increase fire activity significantly. Warmer temperatures and greater evaporation in some places could actually reduce fire risks over time if the result is reduced growth of grasses and other surface vegetation that provide the continuous fuel cover necessary for large fires to spread. The effect of climate change on precipitation is also a major source of uncertainty for fuel-limited fire regimes. However, in some places these are the same ecosystems where fire suppression and land uses that reduce fire activity in the short run have led to increased fuel loads today as formerly open woodlands have become dense forests, increasing for the immediate future the risk of large, difficult-to-control fires with ecologically severe impacts," he explained.
In other words - in already dry areas, you're not likely to get an increase in the number of fires even if temperatures go up. Unusually high precipitation patterns in those areas, however, can cause an uptick in fires by providing the ideal source of fuel. A slight, but essential, distinction, Leonard notes.
What we can all agree on is that California's future - and, to a larger extent, much of the United States' - is more wildfires.
Via ::New Scientist Environment: California wildlifes: Climate change or not? (blog), ::Los Angeles Times: Global warming not a factor in wildfires (newspaper), ::Salon: Cry "fire" and let loose the dogs of climate change! (blog), ::Newsweek Lab Notes: Why California's Wildfires are America's Future (blog)
See also: ::What Turns Fires into Disasters? Politics and Planning, ::Wildfires Causing Further Deterioration of Southern California's Air Quality, ::Southern California Facing "Perfect Drought", ::NASA Satellite Pictures Capture Wildfires' Breadth