peat fire
Forest fires burntheir way into climate change
31 July2003
By Robert C. Cowen
New evidence suggests wildfires are a wild card inclimate change. The chemical junk that forest fires spew into the air mightaffect atmospheric chemistry in a manner similar to – and on a scale similar to- the impact of sulfurous chemicals from volcanic eruptions. This furthercomplicates the complex challenge scientists face in trying to understand what’shappening to Earth’s climate.
Volcanic debris moving through the lower atmospherewashes out fairly quickly. But chemicals that reach the stratosphere spreadaround the world. They undergo reactions that produce a pall of sulfuric aciddroplets. This haze reflects some incoming sunlight and cools the underlyingatmosphere. The effect of a single eruption can last for several years.
Scientists have known that forest-fire smoke alsospreads widely. But they haven’t realized how high it can reach. Now MichaelFromm with Computational Physics in Springfield, Va., and René Servranckx withthe Meteorological Service of Canada in Montreal have found that it, too,penetrates the stratosphere. They published their evidence last week inGeophysical Research Letters.
They show that dense smoke from a 2001 Canadian forestfire reached into the lower stratosphere. There the fire chemicals caused”atmospheric effects similar to those seen during a volcaniceruption,” according to the paper’s announcement. It notes that powerfulupdrafts in so-called “supercell” thunderstorms can carry wildfiredebris to stratospheric heights where it can “affect environmentalconditions, including cloud formation and climate change.”
There can be more than a copycat relationship betweenwildfires and volcanoes. Writing in the same issue of Geophysical ResearchLetters, Baerbel Langmann and Hans Graf at Germany’s Max Planck Institute forMeteorology in Hamburg explain how Indonesian forest fires extend thevolcanic-climate impact. Even when quiescent, Indonesian volcanoes emitsulfurous gases constantly. Rains settle these chemicals into the soil of thelocal peat forests. When the dry season comes, the dried-out peat often catchesfire, releasing the sulfur-containing chemicals back into the atmosphere. Oncethere, thunderstorms can lift them to the stratosphere.
Scientists are only beginning to understand the role ofwildfires in climate change. Yet two points are clear. Their influence onclimate is more subtle than scientists have realized. Moreover, Drs. Fromm andServranckx suggest it is likely to grow as warming temperatures encourage morefire outbreaks in high northern latitudes.
Second, there is a significant difference between thevolcanic and forest-fire wild cards. We can’t control volcanic eruptions. We canminimize wildfires. Many fires result from human carelessness or outmodedslash-and-burn farming. Lack of proper forest maintenance also encouragesconflagrations. It may be difficult to do such maintenance in remote parts ofhigh latitude northern forests. Yet in many other areas, such as the WesternUnited States where fires now rage, there is no excuse to delay fire managementplanning.
Protection of forest resources and the lives andproperty of forest dwellers is reason enough to raise the status of forest firemanagement on the list of national and international priorities. Concern aboutclimate change should enhance the sense of urgency.
