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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 .Atmospheric carbon dioxide levels have now touched 400 parts per million and keep rising.
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3 .So who's responsible?
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4 .Scientists peg the start of this seemingly inexorable rise to about 1750, when people started burning coal to run steam engines.
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5 .But the CO2 increase also stems from activities like clearing forestlands for farming.
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6 .Now a new analysis assigns national blame for CO2 pollution and its ensuing global warming.
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7 .The seven biggest contributors both historically and today are, in alphabetical order: Brazil, China, Germany, India, Russia, the United Kingdom and the United States.
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8 .The report is in the journal Environmental Research Letters.
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9 .The undisputed champion of greenhouse gas pollution is no surprise: the U.S.
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10 .Our emissions to date mean we're responsible for 0.15 degree Celsius of the 0.8 degree Celsius rise in global average temperatures: 19 percent of the total.
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11 .That's more than twice as much as the next highest country, China.
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12 .The worst polluting country per person? The tiny U.K.
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13 .Unfortunately, China looks set to pass the U.S., unless their reliance on coal changes in short order.
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14 .As for us, after several years of our greenhouse gas pollution falling, CO2 emissions rose again in 2013.
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15 .Here's one area in which the U.S.shouldn't want to lead.
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16 .Your minute is up, for Scientific American 60-Second Earth. I'm David Biello.
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