400 ppm …. yikes!
400 ppm is an artificial milestone of course, and yet perhaps also a significant one. We are apparently travelled back in time to the Pliocene, a time roughly 3 million years ago when the earth was a lot warmer and sea level was a lot higher. The global average temperature in the mid-Pliocene was 2-3°C higher than today, and global sea level was a lot … Read more