On May 9, instruments atop Hawaii’s Mauna Loa volcano pegged the atmospheric concentration of carbon dioxide (CO2) — the gas that contributes most to global warming — at slightly above 400 parts per million (ppm).
Carbon Dioxide Hits 400 ppm — Does It Matter?
In May, the amount of CO2 in our atmosphere crossed this long-hyped threshold, setting off a storm of media coverage. But how significant is the milestone?
By Tom Yulsman
Jan 7, 2014 6:25 PMNov 19, 2019 9:36 PM
(Credit: Leonello Calvetti/Shutterstock)
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