Keeling curve

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CO2 Levels Highest in Human History

Carbon dioxide reaches 400ppm milestone

(Newser) - Scientists have been anticipating this milestone for a while, but they won't be breaking out the champagne now that it's here: Carbon-dioxide levels in the atmosphere passed the mark of 400 parts per million yesterday for the first time in human history, reports the BBC . The National Oceanic... More »

Greenhouse Gas Levels About to Hit Bad Milestone

Carbon dioxide ratio in atmosphere close to symbolic 400 parts per million

(Newser) - We're probably going to hear a lot about the "Keeling curve" and references to "400 parts per million" in the coming weeks. The curve measures the ratio of carbon dioxide in the Earth's atmosphere, and that ratio is about to cross the 400-ppm level for the... More »

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