So now soot in the air aids plant growth and fights the scourge of global warming?

Air pollution helps plants blunt climate change: study

Cleaning up skies choked with smog and soot would sharply curtail the capacity of plants to absorb carbon dioxide and blunt global warming, according to a study released on Wednesday.
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"Surprisingly, the effects of atmospheric pollution seem to have enhanced global plant productivity by as much as a quarter from 1960 to 1999," said Linda Mercado, a researcher at the Met Office Hadley Centre in Britain, and the study's lead author.
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The findings underline a cruel dilemma: to the extent we succeed in reducing aerosol pollution in coming decades, we will need to slash global carbon dioxide emissions even more than we would have otherwise.

"Aerosols offset approximately 50 percent of the greenhouse gas warming," Knut Alfsen, research director at the Centre for International Environmental Research in Oslo, Norway, said by phone.
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Any increase above 2.0 C, the panel said, would unleash a maelstrom of human misery, including drought, famine, disease and forced migration.

NASA GISS suggests aerosols play a large role in Arctic warming « Watts Up With That?

Clean air regulations passed in the 1970s, for example, have likely accelerated warming by diminishing the cooling effect of sulfates. Credit: Drew Shindell, Goddard Institute for Space Studies