Like the burning of gasoline in your car, fires release carbonmonoxide, hydrocarbons (molecules made of carbon and hydrogen atoms), andnitrogen oxidesall of which, when exposed to sunlight, take part in thechemical reactions that create ground-level ozone. Unlike the ozone in thestratosphere, which absorbs dangerous ultraviolet light, ozone near theEarths surface is a harmful air pollutant. While urban and industrialcontributions to pollution go on year round, wildfires can add to globalpollution levels in seasonal, intense bursts.
Carbon monoxide observations collected from satellites are a good way totrack the spread of emissions from fires. This pair of images shows globalcarbon monoxide concentrations in the summers of 2004 (top) and 2005 (bottom)collected by the MOPITT (short for Measurements of Pollution in theTroposphere) sensor on NASAs Terrasatellite. A record fire season in Alaska in 2004 spread smoke across theNorthern Hemisphere and elevated carbon monoxide levels across North America andEurope. Red indicates high concentrations, while yellow indicates lowconcentrations. The high levels over China (far right) are caused by industrialand urban pollution.
The record-breaking 2004 fire season coincided with an international researchcampaign that used a combination of ground-, aircraft-, and satellite-basedsensors to study global pollution drift. As part of the research project,scientists used fire detection information from NASA satellites to estimate howmuch pollution the Alaskan fires released, and then used atmospheric chemistryand weather models to predict where the pollution would spread. The researchrevealed that the fires produced approximately 30 teragrams of carbon monoxide(1 teragram is about 2.2 billion pounds), roughly equal to all thehuman-generated carbon monoxide for the entire continental United States duringthe same period. The scientists estimated that the boost in carbon monoxide andother fire-emitted pollutants increased ground-level ozone up to twenty-fivepercent in the northern continental United States, and by up to ten percent inEurope.