But Shindell said Jacobson's model was also the study's "strongest limitation." Many other studies on black carbon's climate influence have used models that have been used in reports by the Intergovernmental Panel on Climate Change.
The new study "is the kind of result I would like to see confirmed in the more road-tested climate models, but it's more than food for thought," Shindell said. "Still, I think that the results are consistent with some other analyses."
They include a paper Shindell published last year in Nature that found a one-two punch of decreasing sulfate emissions -- which help scatter light from the sun, cooling Earth -- and increasing black carbon emissions -- which have the opposite effect -- has "substantially contributed to rapid Arctic warming during the past three decades."
Jacobson said he agreed that "models need to be continuously tested," and noted that the model he used in this study is one he's been refining since 2002, which has formed the basis for several pieces of published research.
Global warming's quicker fix?
Meanwhile, Ramanathan said that Jacobson's conclusion that black carbon might be the second-largest contributor to warming -- behind only CO2 -- tracks with his own experiments based on observations of actual climatic conditions.
While the uncertainty in the results from Jacobson's model and his own experiments is large, Ramanathan said he "wouldn't rule out that black carbon is the second-largest global warmer."
Meanwhile, another group of researchers published a commentary yesterday in the journal Nature Geoscience that argues cutting black carbon, methane and other short-lived substances that influence climate could not only limit warming but improve climate models, if done correctly.
"Earth's climate can only be stabilized by bringing carbon dioxide emissions under control in the twenty-first century," they write. But reducing emissions of short-lived substances that help heat the planet "could significantly reduce the rate of warming over the next few decades."
And by carefully measuring and modeling the resulting changes in atmospheric composition, scientists could improve their estimate of how sensitive Earth's climate is to CO2, said lead author Joyce Penner, a professor of atmospheric science at the University of Michigan whose work focuses on improving global climate models and their ability to model the interplay between clouds and aerosol particles.
That would narrow estimates of how much warming the world can expect for a given level of CO2 in the atmosphere.
"Why should we go another 20 years without knowing whether we're on high [warming] curve or the low curve?" said Penner.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500