What's the Global Fire Trend?

Wildfires that have destroyed more than a thousand homes and threaten thousands more continue to rage every years. Meteorologists point out that drought and an influx of wind from Tropical Storm Lee have fanned the flames and fueled the rash of fires, the most severe Texas has experienced in recent memory.

But what do we know about the broader context of the fires? Can we say with any certainty, for example, that fires have become more common in the United States – and across the globe – in the last few decades as global temperatures have increased?

The answer to that question, I found after hunting through various journal articles and checking in with some of Goddard Space Flight Center's fire specialists, is complex. Satellites offer the most comprehensive and reliable measure of the amount of land burned each year; however, satellite-based records of fire activity are still relatively brief.

The longest fire record I’ve seen published so far, a piece of research authored by Goddard's Louis Giglio and the University of California, Irvine’s James Randerson, goes back about thirteen years, not long enough to make particularly definitive statements about the nature of long-term fire trends. (The launch of the NPOESS Preparatory Project (NPP) will help as it will carry an instrument capable of monitoring fires that should add another five-to-ten years to the long-term record.)

Still, Giglio and his colleagues have pieced together hints of trends that are worth noting. Between 1997 and 2008, they show that the number of hectares burned across the globe has declined a significant amount from a maximum in 1998 to a minimum in 2008 (see graph above). The area burned in the United States, which is less than a percent of the total area burned each year, has seen peaks in 2000 and 2007.

What’s driving the global decline in area burned? The topic is ripe for more research, but when I asked Giglio that question he reminded me that, contrary to what one might expect, increasing global temperatures and drought do not invariably produce increases in fire activity.