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Wildfires Play Bigger Role in Climate Change than Previously Thought

Aug 04, 2014 03:12 PM EDT
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Wildfires and other types of fires involving plant matter play a much bigger role in climate change and human health than previously thought, according to a recent study. Pictured: Colorado wildfire.
(Photo : Reuters)

Wildfires and other types of fires involving plant matter play a much bigger role in climate change and human health than previously thought, according to a recent study.

Scientists have long known that biomass burning - burning forests to create agricultural lands, burning savannah as a ritual, slash-and-burn agriculture and wildfires - figures into climate change and public health. But this study, published in the Journal of Geophysical Research: Atmospheres, is the first to measure the degree of that contribution.

"We calculate that five to 10 percent of worldwide air pollution mortalities are due to biomass burning," Mark Z. Jacobson, a Stanford University professor of Civil and Environmental Engineering, said in a statement. "That means that it causes the premature deaths of about 250,000 people each year."

The map above shows the predicted global warming impact of all anthropogenic emissions, including biomass burning, on global near-surface air temperature since 1850. The map below shows the observed change in global near-surface air temperature since 1900. The average modeled increase in temperature since 1850 is 1.0 K. The average observed increase since 1900 is 0.92 K. Most increases in temperature occur over the Arctic, which is melting quickly.
(Photo : Mark Jacobson) The map above shows the predicted global warming impact of all anthropogenic emissions, including biomass burning, on global near-surface air temperature since 1850. The map below shows the observed change in global near-surface air temperature since 1900. The average modeled increase in temperature since 1850 is 1.0 K. The average observed increase since 1900 is 0.92 K. Most increases in temperature occur over the Arctic, which is melting quickly.

Most carbon emissions linked with global warming are the result of human activities like the burning of fossil fuels. Most people's main concern is carbon dioxide (CO2) emissions, but other forms of carbon include the methane gas (CH4) and the particles generated by wildfires - the tiny bits of soot, called black carbon, and motes of associated substances known as brown carbon.

According to Jacobson and his team, biomass burning accounts for 18 percent of all human-generated carbon emissions.

This research points out that the public's focus should also be on other forms of carbon pollution besides CO2 emissions alone. Black carbon and brown carbon maximize the thermal impacts of biomass burning. They essentially allow this practice to cause much more global warming per unit weight than other human-associated carbon sources.

When these carbon particles enter the minuscule water droplets that form clouds and are then penetrated by sunlight, the carbon absorbs the light energy, creating heat and accelerating evaporation of the droplet. This causes the cloud to dissipate. And since clouds reflect sunlight, cloud dissipation causes more sunlight to transfer to the ground and seas, ultimately resulting in warmer ground and air temperatures.

In addition, carbon particles released from burning biomass settle on snow and ice, contributing to further warming.

"The bottom line is that biomass burning is neither clean nor climate-neutral," Jacobson said. "If you're serious about addressing global warming, you have to deal with biomass burning as well."

Exposure to biomass burning particles is strongly associated with human health problems like cardiovascular disease, respiratory illness, lung cancer, asthma and low birth weights.

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