You claim there is some impending or inevitable catastrophe - what is it? You don't know anything, and all we know is the global temperature is increasing.
I realized something this weekend, out enjoying a beautiful mid-September day, that ultimately even knowing global warming to be true, a large amount of people simply will not care.
We will continue to get weather disasters, but you know what, they're really no more frequent than before. People have short memories. And know what? This is where people as a community adapt. We move communities further from flood zones, or we build office towers that can withstand earthquakes. We know how bad hurricanes can get and learn immensely from each disaster. We've been adapting to catastrophe for centuries.
The other, perhaps less talked about reason, is the net effect for a large amount of people will be more positive. In my area, rarely have we had such beautiful weather into September. We have to deal with a lot of long and harsh winters, so a longer summer or more mild winters would be fully welcomed. Sure, this really sucks for people living in some areas, probably along the oceans. Oh well, you've been living a lot of nice mild days while we toughed out winters inland. Sucks to be you, as with most things on this planet. You'll move when shit happens, even if just slightly inland, as people have been doing for our entire history.