Burning fossil fuels and biomass has a larger impact on climate than scientists had previously estimated, according to a an international research project led from South Korea's Gwangju Institute of Science and Technology, which examined how climate warming results from the incomplete combustion of carbon fuels.
Wildfires and the millions of inefficient stoves across the developing world, along with inefficient internal combustion engines (ICEs) and power generators put out vast quantities of black carbon, a.k.a. soot, into our atmoshpere. It's long been known that "black carbon" clouds rising up into the atmosphere absorb heat and sunlight and shield the ground from sunlight, which prevents water evaporation that stalls the hydrological cycle.
Also known as "dark smoke," clouds of black carbon aren't the only agents of climate change produced by burning of fossil fuels and biomass, according to a ClimateWire report (subscription required). Published last week in the Proceedings of the National Academy of Sciences, the Gwangju U. research team, led by Chul Chung, found that other biomass emissions, especially those from "brown carbon," also have a warming effect on climate globally, one that's been largely overlooked.
Carbon fuel combustion and climate warming
When biomass and fossil fuels are burned, or combusted, "first you see the smoke is black in color when it's flaming," report co-author Veerabhadran Ramanathan was quoted in ClimateWire's report. "Then the smoke after that is whitish. The white stuff is what is called organic particles."
As they reflect sunlight, these organic particle emissions have been presumed to have a cooling effect on climate. Ramanathan, a distinguished climate scientist at the University of California's Scripps Institute of Oceanography and the Gwangju U. researchers found that this "white smoke" isn't as white as it appears and absorbs more energy than many researchers had calculated, thereby underestimating its climate-warming effect.
The research team combined satellite- and aircraft-based remote sensing technology along with ground-level aerosol sensors to determine how much heat brown carbon can absorb. They found that their heating and cooling effects essentially offset each other, so that their net impact is near zero.
The ramification of this is that so-called "climate forcing" due to black carbon emissions is 85 percent higher than what the UN Intergovernmental Panel on Climate Change (IPCC) has estimated, with brown carbon emissions contributing 20 percnet of solar absorption from carbon aerosols.
"What our work means is that our carbonaceous aerosols would heat the planet more and dry out the planet more," ClimateWire quoted Ramanathan.
Greater-than-thought heat absorption from brown carbon emissions can create "devastating feedbacks, especially for wildfires," according to the researchers and other experts.
"The record-breaking wildfires in the western United States are part of a vicious cycle amplified by global warming. Climate change dries the forests and fuels the fires, and the fires fuel climate change," president of the Institute for Governance and Sustainable Development Durwood Zaelke stated in a press release.
Though abundant, the brown carbon particles don't last long in the atmosphere, only remaining there for a few weeks. Other greenhouse gases, such as CO2, in contrast, can remain in the atmosphere for centuries.
Looking to make greater use of the data they've gathered, the research team wants to input it into simulations to find out how the climate effects of black and brown carbon emissions vary in different parts of the world.
Black carbon emissions are a particular concern for the Indian sub-continent and across Asia, as it's thought they can alter, delay and negatively impact the onset of the monsoons, which are vital to agriculture, food production and water supplies. Ramanathan also aims to use the data in simulations in Africa, particularly sub-Saharan Africa, to find out how these aerosols are affecting climate there.