The deniers will point out that the vast amount of CO2 emissions are naturally occurring (95-97%?). The advocates will point out that man-made emissions have never been higher, are increasing rapidly and have/are pushing things over the tipping point at which our planet can recover. Basically arguing that while we may only account for 3-5%, but that's 3-5% that our planet has never had to deal with before.
I think this a huge point. Things in nature while robust and adaptable are still fragile. Take a freshwater lake and make it 5% salt and watch what happens. We have no idea what % could be the tipping point and we probably should try our best not to find out.
Edit, wrote this before seeing your post on tipping points.
Last edited by Sudden_Death; 12-02-2012 at 07:42 PM.