South Pole reaches 400 ppm of carbon dioxide

This graphic shows the rise in daily average carbon dioxide levels at the South Pole to 400 parts per million on May 23. It’s the first time this has happened in at least four million years. Data for 2014-present recorded NOAA’s greenhouse gas monitoring network. Graphic courtesy NOAA.

The concentration of carbon dioxide in the atmosphere above our planet’s South Pole reached the worrisome threshold of 400 parts per million.

At least four million years have past since the last time carbon dioxide was so plentiful in the air above the South Pole, according to a statement announcing the milestone released Wednesday by the National Oceanic & Atmospheric Administration.

No region of Earth remains below the 400 ppm threshold.

“The far southern hemisphere was the last place on earth where CO2 had not yet reached this mark,” Pieter Tans, the lead scientist of NOAA’s Global Greenhouse Gas Reference Network, said. “Global CO2 levels will not return to values below 400 ppm in our lifetimes, and almost certainly for much longer.”

The South Pole is slower to demonstrate increases in atmospheric greenhouse gas concentrations driven by human combustion of fossil fuels because that region is so remote from the populated, and economically developed, areas of Earth.

Another federal government entity, the National Center for Atmospheric Research in Boulder, Colo., recently warned that the South Pole would soon cross the 400 ppm threshold.

This graphic illustrates the atmospheric concentration of carbon dioxide near Antarctica in January, just as air masses over the Southern Ocean began to exceed 400 parts per million of CO2. Graphic courtesy Scripps Institution of Oceanography, illustration by Eric Morgan.

“Throughout humanity, we have lived in an era with CO2 levels below 400 ppm,” Ralph Keeling, director of the CO2 Program at the Scripps Institution of Oceanography, said in an NCAR statement released May 12 . “With these data, we see that era drawing to a close, as the curtain of higher CO2 spreads into the Southern hemisphere from the north. There is no sharp climate threshold at 400 ppm, but this milestone is symbolically and psychologically important.”

NOAA data obtained at the South Pole indicates that the atmospheric concentration of carbon dioxide there was about 336 ppm in 1980 and has generally been rising since that time.