A new study from the University of Wyoming suggests that the wave of South African wildfires that usually take place around the summer months has had an unexpectedly positive effect, one that could counter the ongoing problem of global warming.
Previous research had suggested that smoke has an overall negative effect on how clouds cool the environment, as it would absorb light that would normally be reflected by clouds located below the aerosols. While the new research did not exactly contest that effect, the researchers did observe that clouds were more reflective of light than once thought, thereby giving them a climate cooling effect. According to the University of Wyoming website, this is because the smoke from South African wildfires was observed to be closer to cloud layers than expected, with the aerosol particles from the smoke allowing cloud droplets to form.
“If you change the particles, you are changing the composition of the cloud,” read a statement from University of Wyoming professor Xiaohong Liu that explained the findings of the new paper.
“For our study, we found the smoke comes down and can mix within the clouds. The changed clouds are more reflective of sunlight. Brighter clouds counteract the greenhouse effect. It creates cooling.”
Using computer modeling to come up with the figures, Liu stated that the greenhouse effect of human activities since the start of the industrial era is at 1.66 watts per square meter, with that figure evenly distributed across the planet. This figure, however, is trumped by the cooling effect of fire smoke, which was estimated to be approximately seven watts per square meter, albeit over a select region (the southeast Atlantic) and specifically during the annual fire season. As further explained to Liu, his team’s research, which was published Monday in the Proceedings of the National Academy of Sciences, is the first to provide some figures to back up the cooling effect of smoke aerosols in clouds.
South African wildfires make up the bulk of events that take place during the country’s fire season, which starts in July and ends in October. These fires, as well as those that are purposely set in order to clear farmland, emit biomass-burning aerosols that move west toward the southeast Atlantic Ocean and intermingle with stratocumulus clouds found about one kilometer above sea level. Once this happens, the clouds become brighter and result in the climate cooling effect observed in the new study.
The idea of aerosols cooling the world’s climate is nothing new. A NASA article noted that they can sometimes work in concert with the clouds they seed and influence Earth’s climate by reflecting about a fourth of the sun’s energy back to space. However, the article also noted that the overall “direct effect” of aerosols on our planet’s radiation field could be complex, as there are some aerosols that absorb sunlight instead of reflecting it.
Going forward, Liu and his colleagues are hoping to go beyond the South African wildfires observed in their study as they seek to improve global climate models by providing more accurate measurements of how clouds interact with aerosols from cars, power plants, and other sources. The researchers also plan to determine how much our planet’s climate has been cooled by smoke aerosols, and if the phenomenon had somehow slowed down, or masked the global warming brought on by greenhouse gases.