"Droughts over Indonesia are often brought on by a shift in the atmospheric circulation over the tropical Pacific associated with El Nino conditions," said David Edwards, of the National Center for Atmospheric Research in Boulder, Colo. "Although the current El Nino is rather weak compared to that of 1997-98, we have found dramatic increases in wildfire activity and corresponding pollution."
Edwards and his colleagues used NASA satellite and rainfall data for their research.
When rainfall sharply decreased during the last quarter of 2006 in Indonesia's tropical rainforests, the exceptionally dry conditions allowed wildfires to spread, and large amounts of soot and dust delivered unhealthy pollution levels to the area, he said.
The Measurements of Pollution in the Troposphere (MOPITT) instrument aboard NASA's Terra satellite tracked wildfire pollution plumes spreading from Indonesia to the Indian Ocean and measured increases in carbon monoxide levels, NASA reported.
"Even though fires in South America and southern Africa typically produce the greatest amount of carbon monoxide, the pollution from Indonesian fires is likely responsible for most of the year-to-year variation in pollution levels throughout the Southern Hemisphere," Edwards said.