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When soot particles emerge from the smokestack of a cargo ship, where do they go? And how do they affect the atmosphere? Those traveling particles are among many aerosols that Hailong Wang studies to determine their role in Earth's climate.

Some aerosol types, such as black carbon, absorb light and can cause melting when they land on snow and ice. Others, like sulfate, can form a layer in the air that reflects sunlight back into the atmosphere. Wang is working to improve how these complex aerosol effects are represented in climate models.

According to a 2019 study by Wang and colleagues, the drop in snow cover over land and sea ice accounted for about 70 percent of the satellite-observed reduction in Arctic surface reflectiveness since the 1980s. This research challenged the traditional view that diminishing sea ice retreat was the primary driver of the change in how much sunlight is reflected into the atmosphere from the Arctic surface.

Wang has also developed a method for tagging sources of emissions, attributing them to specific regions or economic sectors.

“Our aerosol source tagging can show how the air quality and climate will respond to changing emissions from specific regions or sectors,” Wang said. “This can provide guidance for policymakers when they plan climate change mitigation strategies.”

He has worked on improvements to Earth system models such as the Energy Exascale Earth System Model. The updated versions of these models have been widely used to better understand and quantify the effects of aerosols on cloud formation, precipitation, air quality, and climate. He is also investigating whether injecting aerosols into clouds—a form of geoengineering—could help enhance their reflectiveness, a concept known as cloud brightening.

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“Ice loss causing Arctic to reflect less heat.” November 11, 2019, BBC News.