I think that man can be pretty clever when we have an obstacle to overcome.
Heat is a wonderful resource and I would bet they could think of better things to do with it than dissipate it. When dissipation is absolutely necessary, there are lots of places to put it: oceans (who cares what temperature the ocean gets? if it boils away that makes more land surface.), mantle, outside air (again, once you decide to do away with the ecosphere, who cares what temp the air gets to?), space. We have known for a long time that you don't need arable land to make food.
Also man can be pretty clever when it comes to making compromises and accepting a lower standard of living.