NOAA, June 15, 2016: “The Earth passed another unfortunate milestone May 23 when carbon dioxide surpassed 400 parts per million (ppm) at the South Pole for the first time in 4 million years. The South Pole has shown the same, relentless upward trend in carbon dioxide (CO₂) as the rest of world, but its remote location means it’s the last to register the impacts of increasing emissions from fossil fuel consumption, the primary driver of greenhouse gas pollution.   “The far southern hemisphere was the last place on earth where CO₂ had not yet reached this mark,” said Pieter Tans, the lead scientist of NOAA’s Global Greenhouse Gas Reference Network. “Global CO₂ levels will not return to values below 400 ppm in our lifetimes, and almost certainly for much longer.”