What has to happen regarding climate change so that governments will accept drastic measures?

The only way governments will accept drastic measures to change anything is if politicians realize that it is in their political interest to do so. Politicians will overwhelmingly make decisions and apply pressure for change in accordance with what will get them reelected. I don't think governmental systems or processes will be the catalyst for the kinds of drastic change we need to happen. It will need to originate from society. Attitudes will need to radically shift in relation to our natural world before policies and money follows suit. Unfortunately, shifts in attitudes and worldviews tend to take place only gradually and incrementally. To galvanize world opinion in favor of placing environmental concerns at the forefront, ultimately I think we will need to experience a series of natural disasters. Perhaps then, people will have no choice but to pay attention.