CO2 concentration reaches 400 ppm
This is historical : carbon dioxide concentration has reached in several places over the arctic a concentration of 400 parts per million. This doesn’t seem to be much, but pre-industrial levels were of 280 ppm.
As you might remember, the safe level is considered by the scientific community to be at 350 ppm. CO2 concentration keeps on increasing by two or three parts per million per year, pressing even more greenhouse gases emissions cuts.