Scientists using NASA satellite data have found the most intense global pollution from fires occurred during droughts caused by El Nino. The most intense fires took place in 1997-1998 in association with the strongest El Nino event of the 20th century.
Bryan Duncan, Randall Martin, Amanda Staudt, Rosemarie Yevich and Jennifer Logan, from Harvard University, used data observed by NASA's Total Ozone Mapping Spectrometer (TOMS) satellite to quantify the amount of smoke pollution from biomass burning over 20 years.
"It's important to study biomass burning, because those fires produce as much pollution as use of fossil fuels. Most of the pollution from fires is produced in the tropics, while pollution from fossil fuel use occurs in North America, Europe and Asia," Logan said.
One of the missions of NASA's Earth Science Enterprise, which partially funded the research, is to learn how the Earth system responds to natural and human-induced changes, such as droughts and worldwide fires caused by El Nino. NASA's Goddard Space Flight Center, Greenbelt, Md, developed the smoke data, the unique Aerosol Index product from the TOMS satellite.
The Harvard scientists recently published a study in the Journal of Geophysical Research — Atmospheres that describes how they combined the Aerosol Index data from TOMS with Scanning Radiometer and Sounder (ASTR) fire count data from the European Space Agency's European Remote Sensing-2 satellite.
The study assessed the effects of the 1997-1998 El Nino events on global biomass burning. They concluded biomass burning around the world was unusually high during the 1997-1998 El Nino, greater than in any other period between 1979 and 2000. The amount of carbon monoxide emitted in 1997 and 1998 was about 30 percent higher than the amount emitted from worldwide motor vehicle and fossil fuel combustion.
"We found that fires typically produce the most pollution in Southeast Asia in March, in northern Africa in January and February, and in southern Africa and Brazil in August and September," Logan said. During the El Nino of 1997-1998, Indonesia, Mexico, and Central America experienced extreme droughts, and forest fires raged out of control.
The smoke from the fires in Mexico and Central America was blown northward in May 1998, worsening air-quality and reducing visibility over much of the eastern United States. The fires in Indonesia burned tropical forests over an area equivalent to the size of southern New England and released enormous amounts of pollutants. The team estimated the Indonesian fires produced about 170 million metric tons of carbon monoxide, which equals about one-third of the carbon monoxide annually released from fossil fuels.
Biomass burning is the combustion of both living and dead vegetation. It includes fires generated both by lightning and human activity. Humans are responsible for about 90 percent of biomass burning, with only a small percentage of natural fires contributing to the total amount of vegetation burned.
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