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1 .This is Scientific American 60-Second Earth. I'm David Biello. Your minute begins now.
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2 .On March 12, researchers reported that carbon dioxide concentrations in the atmosphere moved above 400 parts-per-million en route to a springtime peak.
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3 .During spring, trees and other plants begin to draw down CO2 levels to fuel leaf growth.
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4 .But this is the second time in as many years that levels have risen above 400 ppm,
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5 .a mark never before experienced in the entire time our species has walked the Earth.
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6 .So the important question is: exactly how sensitive is the Earth's climate to these ever-increasing greenhouse gases?
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7 .Will warming happen gradually or quickly, and to what extent?
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8 .Even more importantly, how can we find out without the potentially catastrophic experiment we are presently running?
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9 .A recent study suggests that other greenhouse gases may be the key to answering this question.
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10 .Specifically soot-like air pollution and ozone.
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11 .Taking into account the unique characteristics of this localized air pollution suggests that the climate is "very unlikely" to be insensitive.
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12 .The research appears in the journal Nature Climate Change.
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13 .That means climate change with an increase of more than a degree Celsius compared with the last century is very likely already.
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14 .It's going to take cutting out most further greenhouse gas pollution to restrain further global warming.
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15 .Your minute is up, for Scientific American 60-Second Earth. I'm David Biello.
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