The issue is that it has become a political issue before we were sure what the issue was. Now we don't know whether or not we should act, instead of deciding what we should do.
Well, it was a plausible scenario, if not definitely certain. It would have been wise to reduce the worldwide emission of greenhouse gases while the science was being done, but were in a typical prisoner dilemma situation here, and convincing everyone has proven impossible (notoriously because of the USA, China, India and probably others).