We have many trillions of dollars sunk into infrastructure that depends on the local environment being what it was when the infrastructure was designed and built. If the environment changes significantly in its average or peak temperature levels, or its humidity, or its solar radiation, or any of a range of other environmental factors, then the infrastructure may see reduced functionality, increased wear, or outright failure. As climate changes start to make themselves known in earnest we will have to start chasing them to patch up all of this infrastructure which imposes a tremendous cost on us. Instead of maintaining our existing bridges, road systems and hospitals we will need to come up with a hasty plan to relocate the Netherlands, build sea walls around Manhattan, allocate new areas and develop them to house everyone who needs to leave their old homes on the Equator, etc.
While the Antarctic may eventually become habitable, relocating e.g. a hundred million displaced Chinese there is going to be tremendously expensive and a huge drag on the global economy that we might have avoided with relative ease by simply stopping coal subsidies and letting market forces phase in solar for us.