The level of heat-trapping carbon dioxide in Earth’s atmosphere has reached an average 400 parts per million, an historic level not seen since at least three million years ago, scientists reported on Friday.
From the New York Times:
Carbon dioxide above 400 parts per million was first seen in the Arctic last year, and had also spiked above that level in hourly readings at Mauna Loa. But the average reading for an entire day surpassed that level at Mauna Loa for the first time in the 24 hours that ended at 8 P.M. Eastern Daylight Time on Thursday, according to data from both NOAA and Scripps.
Carbon dioxide rises and falls on a seasonal cycle and the level will dip below 400 this summer, as leaf growth in the Northern Hemisphere pulls about 10 billion tons of carbon out of the air. But experts say that will be a brief reprieve — the moment is approaching when no measurement of the ambient air anywhere on earth, in any season, will produce a reading below 400.
“It feels like the inevitable march toward disaster,” said Maureen E. Raymo, a Columbia University earth scientist.
