That&#39;s my understanding, Lorne. As I&#39;ve wr...

That's my understanding, Lorne. As I've written before there's no way of knowing for sure if we've actually crossed a climate "tipping point" that triggers natural feedback mechanisms and, potentially, runaway climate change.

The 2C target is supposed to give us a 66% chance of avoiding runaway global warming but it's based on a load of assumptions that could be optimistic. What's been going on in the Arctic, especially over the past decade, leaves me unsure.

The leading expert on the Greenland Ice Sheet, Jason Box, sees a "feedback loop" already underway. The warming Arctic is resulting in more wildfires that are covering the ice sheet in soot, leaving it ever darker. That accelerates warming and melting, increasing sea level rise. Warming Arctic water temperatures are impacting on glacier calving rates.

http://www.independent.co.uk/environment/greenlands-dark-snow-may-start-global-warming-feedback-loop-9742159.html

Box recently reported that sea level rise due to melting of the Greenland ice sheet is now doubling every five to ten years. If he's right and there's no way to arrest this Arctic black soot problem then, perhaps, all bets are off on runaway climate change.