Colonization of planets (and much more likely, space habitats) off Earth *could* help rein in global warming, in the mid-term, by moving heavily polluting industrial activity off earth. I'd guess we're, best case, 200 years off being able to really move people off Earth in sufficient numbers to matter. We need to solve the problem before then.

But I object to the idea that it's all-or-nothing. We can curb population. We can restrain the release of carbon and methane into the atmosphere. We can recapture carbon. We can put sunshades in the atmosphere, or in orbit. We almost certainly *will* do all of those things.

But it's dreadfully, probably fatally short-sighted, to skip the colonization of the solar system while we're at it. 350 10-million capacity O'Neill's could move half the current population of the planet off Earth. A space elevator would make it possible to get them there, for a reasonable price. Even if, by the time we get there, the population pressures have ceased? What, we gave the human race a future off Earth when we didn't desperately have to? I can live with that.