It may be a see-saw course, but it’s riding an uphill train. A bit ago I wrote , regarding climate and tipping points: The concept of “tipping point” — a change beyond which there’s no turning back — comes up a lot in climate discussions. An obvious tipping point involves polar ice. If the earth keeps warming — both in the atmosphere and in the ocean — at some point a full and permanent melt of Arctic and Antarctic ice is inevitable. Permanent ice first started forming in the Antarctic about 35 million years ago, thanks to global cooling which crossed a tipping point for ice formation. That’s not very long ago. During the 200 million years before that, the earth was too warm for permanent ice to form, at least as far as we know. We’re now going the other direction, rewarming the earth, and permanent ice is […]