A new study has found that as the climate gets warmer and dryer, forest fires will become as much as three times more common in parts of the American West, which would impact air quality and damage human lungs.
Even as forest fires seem to be appearing more often in media reports, scientists only began documenting the extent of the trend in the last few years.
According to a report in Discovery News, records now show that, in the western United States, the amount of area burned annually by fires was more than six times higher between 1987 and 2003 than it was between 1970 and 1986.
Increases have also been documented in Canada and Alaska.
Scientists know that burning wood and underbrush spews gasses and particles into the air that are pushed around by winds.
Those particles can irritate lungs but are especially dangerous to people who have trouble breathing as a result of asthma and other chronic conditions.
Figuring out just how much pollution a fire emits, however, is complicated.
The relationship depends on the types of wood involved, how hot the air is, how much fuel is lying around on the ground and more.
The researchers looked at 25 years' worth of fire records to first quantify how big a fire will become given weather-based factors like temperature and humidity.
sing standard climate models to project the future, they estimated that by the 2050s, fires could burn 80 percent more area in the Pacific Northwest.
In the Rocky Mountains, fires could burn 175 percent more land. Overall, an average of 50 percent more area could burn across the American West.
From there, the researchers created another computer model that combined future fire projections with previous calculations linking fires with the amount of carbon emissions they produced.
The model estimated a 40 percent rise in lung-irritating carbon aerosols by the 2050s.
"Going into this, we expected to see an increase in forest fires simply because temperatures are going to be warmer 40 or 50 years from now," said Jennifer Logan, an atmospheric chemist at Harvard University in Cambridge, Massachusetts.
"We didn't know how big it was going to be and we didn't know what affect it was going to have on air quality," he added.
According to Gabriele Pfister, an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colorado, "We have to be aware that because of our impact on the environment, we are having an impact on these fires as well.
If they get worse, they're not natural anymore."