South African Wildfires Are Cooling The Earth

Posted: Mar 6 2018, 3:58am CST | by , Updated: Mar 6 2018, 4:44am CST, in News | Latest Science News

South African Wildfires are Unexpectedly Cooling The Earth
Credit: NASA/Kirk Knobelspiesse

New study says that fire smoke combined with low-level clouds creates a reflective process that actually helps cool climate and counteract the greenhouse effect

Researchers have found that South African wildfires may be playing a role in cooling Earth’s climate. In the latest study published by University of Wyoming, researchers describe how the wildfire smoke originating from South Africa interacts with the clouds over Atlantic Ocean and significantly enhances their brightness, which in turn creates a reflective process that sends sunlight back into the space and results in a cooling effect.

“If you change the particles, you are changing the composition of the cloud,” said Xiaohong Liu, a professor in the Department of Atmospheric Science in Wyoming University. 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.”

Scientists have already established that different types of clouds affect the Earth's climate in a different manner. For instance, low-lying clouds help cool the Earth. However, until now, no positive connection between biomass smoke and cloud’s ability to reflect heat was ever made. In fact, scientists believed that overall, the smoke reduces the clouds' cooling effect by absorbing light that the clouds beneath otherwise would reflect. However, new findings contradict the previous understanding and have implications for global climate models.

"The purpose of this paper is to look at these competing processes. Which one is more important?" asks Zhibo Zhang, a co-author of the study.

To investigate the phenomenon, researchers used data from a LiDAR system on the International Space Station that measures the location, composition and distribution of pollution, dust, smoke, aerosols and other particulates in the atmosphere. Wildfires in central and southern Africa usually get more intense from July through October and create so much smoke that it's clearly visible from space.

When researchers looked at the data, they found that that South African wildfire smoke and cloud layers are much closer to each other than previously observed. That means that the smoke can physically interact with the clouds, changing their composition and accelerating their cooling effect.

By running advanced computer model, researchers calculated that wildfire smoke produces a much larger cooling effect: 7 watts per square meter over the southeast Atlantic during the fire season of each year.

“Our group is the first to quantify this brightening effect,” said Liu. “This (smoke aerosols in clouds) reflects more solar radiation to space, which results in less solar radiation reaching the Earth’s surface. This creates a cooling effect.”

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Hira Bashir covers daily affairs around the world.




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