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Carbon Dioxide Measurements Could Pass 400 ppm By Mid-May, Warn NOAA Researchers

Apr 30, 2013 01:57 PM EDT

Carbon dioxide measurements at the Mauna Loa observatory in Hawaii are liable to cross the 400 parts per million (ppm) by mid-May, warn researchers from the Earth System Research Laboratory for the National Oceanic and Atmospheric Administration (NOAA).

The graph, updated weekly, showed a daily average of 399.72 ppm on April 25. The weekly average posted on Monday was that of 398.5 ppm with several hourly readings jumping north of the 400 ppm threshold.

The last time the Earth reached what scientists consider to be a symbolic milestone - that of 400 ppm - was the geologic era between 3 million and 5 million years ago known as the Pilocene epoch.

Based on fossil records, scientists estimate the world’s climate during this period was generally warmer and wetter than today with savannas and woodlands covering what is now the North African desert and tropical and subtropical marine life inhabiting areas northward along the U.S. Eastern Seaboard.

The period was also marked by frequent, intense El Nino cycles, which caused intense flooding as well as an absence of significant ocean upwelling. This in turn would have suppressed fisheries along the west coasts of the Americas and deprived seabirds and marine mammals of food, according to the Scripps Institute of Oceanography.

However, while carbon dioxide levels may compare to those of the Pilocene era, what doesn’t compare is the speed at which the Earth is currently surpassing 400 ppm today, according to geologist Richard Norris. Previously, it took as long as 1,000 years or more for the world to experience a 10 ppm increase; now the planet is poised to reach the 1,000 ppm level in just 100 years should current trajectories remain steady.

Still, Norris believes the same ecosystem changes will occur, with the main lagging indicator being the sea level due to the long period of time needed to heat the world’s oceans and melt the ice.

“Our grandchildren will inhabit a radically altered planet, as the ocean gradually warms up in the response to the buildup of heat-trapping gases,” said Scripps geoscientist Jeff Severinghaus.

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