In fact, many climate scientists have been warning about atmospheric carbon levels passing 400 parts per million — which happened last year. (dailycaller.com)
The new research shows atmospheric carbon levels returned to normal within a few thousand years after the first pulse, probably as carbon dissolved in the ocean. (sciencedaily.com)
It is tough to stay positive when atmospheric carbon levels seem to be rising with no end in sight. (kleinmanenergy.upenn.edu)