Earth CO2 levels: Have we crossed a point of no return?

Categories: Big picture
Published on: October 2, 2016

The Christian Science Monitor / Weston Williams / 28 September 2016

co2-400ppm_standard“The last time our planet saw 400 ppm carbon dioxide in our atmosphere was about 3.5 million years ago, and global climate was distinctly different than today,” David Black, associate professor in the School of Marine and Atmospheric Sciences at Stony Brook University in New York, tells The Christian Science Monitor in an email.

“In particular, the Arctic (north of 60°) was substantially warmer than present, and global sea level was anywhere between 15 and 90 feet higher than today,” Professor Black says.

“It took millions of years for the atmosphere to reach 400 ppm CO2 back then, and it took millions of years for the atmospheric CO2 to drop to 280 ppm right before the industrial revolution. One of the things that really concerns climate scientists is we as humans have taken only a few centuries to do what nature took millions of years, and most of that change was just in the last 50-60 years.”

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