Figures released by the National Oceanic and Atmospheric Administration show that Antarctica's South Pole Observatory carbon dioxide observing station cleared 400 ppm (parts per million) on May 23, 2016. This is the final, and most remote, monitoring station in the world to reach this level. This concentration has not occurred in over 4 million years.
2016 May 23, 400 Part Per Million Reached in Antarctica
Edition of 5
Pigment ink on cotton rag