I went to a cross european political seminar on this and other global warming effects and generally the answer is that while it might get pretty bad, we are on

I went to a cross european political seminar on this and other global warming effects and generally the answer is that while it might get pretty bad, we are on target for 4 or so degrees of warming if we stopped all our existing climate control measures. However, the effects at this level of warming are very much unknowns and things like the permafrost releasing a terrible exponential effect are theorised possibilities but very much untestable hypothesis. However, we tend to assume this won't happen, for various reasons. It's more of an unlikely worst-case scenario. I like to think of it as similar to the people who theorised that CERN could produce a black hole or that atmospheric testing of nuclear weapons could cause the entire atmosphere to ignite. They were broadly plausable if a little far fetched, but ultimately the only way to be sure was to test it. One of the important things to remember is that we have made significant progress towards the 'hole in the ozone layer' to the point where you dont hear about it much anymore because its actually getting better - that is, the hole is closing up. Its possible that a mixure of good science and public policy could deal with this problem as well, although it is closely tied with politics. Especially the fact that the largest polluter in the planet (China) is on track to increase its pollution exponentially. If we can deal with this problem, much of our estimates will be revised down a lot.