"If you believe that anthropogenic climate change is going to be a global disaster, you should probably reasonably assume that some country in the world is going to allocate serious resources to mitigating it."

Not when mitigating it requires ending and reversing economic growth. You're assuming there's a single nation on Earth run by good-faith actors. Furthermore, if climate-drive austerity doesn't occur, the Earth will kill billions of people until it reaches a new equilibrium.