A new study by Indian glaciologists suggests black carbon from forest fires may affect the “reflectance” or albedo of glaciers in a manner that reduces their mass balance. The report indicates that the change in reflectance in 2009 was higher than in any other year from 2000 to 2012 and could only be explained by the extensive forest fires that year, the number of which was significantly higher than any other year between 2001 and 2010. The scientists noted that many small low-altitude Himalayan glaciers are currently melting by as much as 1 meter per year, more than double previous estimates.
In addition to the Indian study, a new study conducted by researchers at the Los Alamos National Laboratory has found that climate models have underestimated the contribution of wildfires to global warming. Existing climate models assume that wildfires emit a mixture of warming black carbon particles along with organic carbon, thought to cause cooling by reflecting sunlight. The combination and ratio of the two types of particles was thought to cause net cooling or a neutral climate effect.
The researchers, who began looking at wildfires after the 2011 Las Conchas fire threatened their own laboratory, found that wildfires also emit tiny, black balls of tar, at a rate ten times higher than these other particles. Further the black and organic carbon emitted by the fires are covered in an organic coating which acts like a lens to focus sunlight, increasing the warming by a factor of 2 or more.
A series of studies led by Dr. V. Ramanathan of Scripps Institute of Oceanography have also found that that co-called brown carbon has a more a potent warming impact than many models account for, offsetting up to 60 to 90% of the cooling caused by other lighter organic carbons. Based on recent field studies Dr. Ramanathan and co-researchers estimate that the warming contribution of brown carbon causes organic carbon’s net impact to be close to zero, meaning that it does not offset the warming caused by co-emitted black carbon, which has been estimated to be the second most powerful climate forcer, behind only CO2.
“The combination of these findings has important implications for climate models and climate mitigation,” said Durwood Zaelke, President of the Institute for Governance & Sustainable Development. “Wildfires and agricultural burning in Africa, Asia, and South America, once thought to have little or no effect on the climate may contribute significantly to global warming.”
“Wildfires are only expected to increase as the climate warms,” added Zaelke. “So urgent action to reduce the rate of warming immediately can contribute to limiting such positive feedbacks, where the consequences of increased warming, such as forest fires, themselves increase warming.
The Divecha Centre study is here.
The Nature Communications study is here.
IGSD’s Primer on Short-Lived Climate Pollutants is here.
