Carbon dioxide levels hit landmark in Northern Hemisphere

Half the world sees full month at or above symbolic 400 parts per million CO2 level

By Beth Mole, 16:41 PM May 28, 2014

April was the first month in recorded history with average carbon dioxide levels at or above 400 parts per million across the Northern Hemisphere, according to a May 26 announcement by the World Meteorological Organization.

Climate scientists first recorded the troubling peak in the greenhouse gas in the Arctic in 2012 and in Hawaii last year (SN: 12/28/2013, p. 26), but the rest of the globe had yet to consistently hit the high mark. The 400 ppm level is largely symbolic, representing nearly ...

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