The carbon dioxide content of the Earth's atmosphere was 411.276 parts per million (ppm) on May 15. On that date one year ago the count was 406.97 ppm.

A record high of 412.63 ppm was recorded on April 26.

"Scientific American" magazine had this to say about the April 18 reading, the first time the measurement passed the 410 ppm mark: "On April 18, the Mauna Loa Observatory recorded its first-ever carbon dioxide reading in excess of 410 parts per million (it was 410.28 ppm in case you want the full deal). Carbon dioxide hasn't reached that height in millions of years."

Measurements are made by two independent CO2 monitoring programs (NOAA and Scripps) at the Mauna Loa Observatory in Hawaii, about 3,400 metres above sea level.


"We're just entering a new era in earth's history," Dr. Shakun said (Dr. Jeremy Shakun, Harvard). "It will be an unrecognizable new planet in the future. I think the only question is, exactly how fast does that transformation happen?"

New York Times, April 12, 2017, Justin Gillis writing about climate