Jacobson's climate model is the first global model to use mathematical equations to describe the physical and chemical interactions of soot particles in cloud droplets in the atmosphere. This allowed him to include details such as light bouncing around inside clouds and within cloud drops, which he said are critical for understanding the full effect of black carbon on heating the atmosphere.
"The key to modeling the climate effects of soot is to account for all of its effects on clouds, sea ice, snow, and atmospheric heating," Jacobson said. Because of the complexity of the processes, he said it is not a surprise that previous models have not correctly treated the physical interactions required to simulate cloud, snow, and atmospheric heating by soot. "But without treating these processes, no model can give the correct answer with respect to soot's effects," he said.
Jacobson argues that leaving out this scale of detail in other models has led many scientists and policy makers to undervalue the role of black carbon as a warming agent.
The strong global heating due to soot that Jacobson found is supported by some recent findings of Veerabhadran Ramanathan, a professor of climate and atmospheric science at the Scripps Institute of Oceanography, who measures and models the climate effects of soot.
"Jacobson's study is the first time that a model has looked at the various ways black carbon can impact climate in a quantitative way," said Ramanathan, who was not involved in the study.
Black carbon has an especially potent warming effect over the Arctic. When black carbon is present in the air over snow or ice, su
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