Fresh research led by scientists at the University of Leeds has shown that the effects of fires in the pre-industrial era, which realised particles in the earth's atmosphere, may have been significantly underestimated.
The University believes that these new findings imply that the cooling effect of present-day man-made aerosol pollution, such as the tiny particles in car emissions and power plant stacks, may have been overestimated.
"Fires cause large amounts of tiny particles, known as aerosols, to be released into the atmosphere," the report suggested. "These aerosols, such as the soot in smoke or chemicals released by burning trees, can cool the planet by reflecting sunlight back into space and increasing cloud brightness."
Lead author of the study, Dr Douglas Hamilton, carried out this research while at the School of Earth and Environment at Leeds. He believes that fires from agricultural burning practices in the pre-industrial era have been largely negated or underestimated in datasets of fire emissions. Therefore, he thinks it was thought there were lower levels of aerosols in the atmosphere, reducing their effect on the climate.
"We know aerosols in the atmosphere have always had a significant impact on climate, but until now, the influence they had historically has been underestimated," he said.
"Our findings show there may be a significant gap between previous estimations and what was actually taking place in the pre-industrial atmosphere."
He said that this suggests the high possibility of a much smaller difference in aerosol cooling between pre-industrial and present-day than we have previously thought.
Using fire models that incorporate a more robust understanding of how humans influence global fire activity, the team was able to re-assess pre-industrial fire occurrence and estimate what the levels of subsequent aerosol emission were in 1750.
When incorporated into a global aerosol model, the fire models showed a substantial difference in atmospheric composition that has not been accounted for in climate models.
"Scientists around the world use models to predict atmospheric conditions in the past. We believe these models need to be updated to take into account our new evidence," he added.
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