Forest fires burn their way into climate change

New evidence suggests wildfires are a wild card in climate change. The chemical junk that forest fires spew into the air might affect atmospheric chemistry in a manner similar to - and on a scale similar to - the impact of sulfurous chemicals from volcanic eruptions. This further complicates the complex challenge scientists face in trying to understand what's happening to Earth's climate.

Volcanic debris moving through the lower atmosphere washes out fairly quickly. But chemicals that reach the stratosphere spread around the world. They undergo reactions that produce a pall of sulfuric acid droplets. This haze reflects some incoming sunlight and cools the underlying atmosphere. The effect of a single eruption can last for several years.

Scientists have known that forest-fire smoke also spreads widely. But they haven't realized how high it can reach. Now Michael Fromm with Computational Physics in Springfield, Va., and René Servranckx with the Meteorological Service of Canada in Montreal have found that it, too, penetrates the stratosphere. They published their evidence last week in Geophysical Research Letters.

They show that dense smoke from a 2001 Canadian forest fire reached into the lower stratosphere. There the fire chemicals caused "atmospheric effects similar to those seen during a volcanic eruption," according to the paper's announcement. It notes that powerful updrafts in so-called "supercell" thunderstorms can carry wildfire debris to stratospheric heights where it can "affect environmental conditions, including cloud formation and climate change."

There can be more than a copycat relationship between wildfires and volcanoes. Writing in the same issue of Geophysical Research Letters, Baerbel Langmann and Hans Graf at Germany's Max Planck Institute for Meteorology in Hamburg explain how Indonesian forest fires extend the volcanic-climate impact. Even when quiescent, Indonesian volcanoes emit sulfurous gases constantly. Rains settle these chemicals into the soil of the local peat forests. When the dry season comes, the dried-out peat often catches fire, releasing the sulfur-containing chemicals back into the atmosphere. Once there, thunderstorms can lift them to the stratosphere.

Scientists are only beginning to understand the role of wildfires in climate change. Yet two points are clear. Their influence on climate is more subtle than scientists have realized. Moreover, Drs. Fromm and Servranckx suggest it is likely to grow as warming temperatures encourage more fire outbreaks in high northern latitudes.

Second, there is a significant difference between the volcanic and forest-fire wild cards. We can't control volcanic eruptions. We can minimize wildfires. Many fires result from human carelessness or outmoded slash-and-burn farming. Lack of proper forest maintenance also encourages conflagrations. It may be difficult to do such maintenance in remote parts of high latitude northern forests. Yet in many other areas, such as the Western United States where fires now rage, there is no excuse to delay fire management planning.

Protection of forest resources and the lives and property of forest dwellers is reason enough to raise the status of forest fire management on the list of national and international priorities. Concern about climate change should enhance the sense of urgency.

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