Global concentrations of the greenhouse gas carbon dioxide are measured at Hawaii’s Mauna Loa Observatory as part of the famous “Keeling Curve” record. Readings could hit the symbolic milestone of 400 parts per million of CO2 in air this month. Scripps Oceanography created a website, keelingcurve.ucsd.edu and a Twitter feed @keeling_curve to update daily readings.
Several news organizations have reported on the impending milestone:
As CO2 Concentrations Near Ominous Benchmark, Daily Updates Begin – Scientific American
Global carbon dioxide levels set to pass 400ppm milestone – The Guardian
CO2-Allzeithoch, Sauerfisch, Religionskrieg – Frankfurter Allgemeine Zeitung