Justin Gillis had a great piece on trees and carbon dioxide in the NYT. The basic shape of things is this. Plants remove carbon dioxide from the atmosphere. So where you have a great big lush forest, you have a powerful engine to partially offset the greenhouse gas emissions associated with burning fossil fuels. But there’s a problem. When weather patterns shift sharply, forests have a way of dying off. New bugs come into place that destroy them. Or they don’t get the right amounts of water at the right time. If a forest dies somewhere, presumably something new will eventually grow in its place. But great big trees take many years to grow big, so when there’s a big die-off you have a reduction in the planet’s ability to absorb greenhouse gas emissions. It’s a reduction that further accelerates the process of warming.
This kind of thing is what’s really scary about the climate science that’s out there. The central tendency forecast of what we think is most likely to happen is pretty scary. But there also appear to be difficult-to-quantify risks of tripping self-reinforcing cycles that could put us a fast track to disaster.