Serious consideration is being given to technological solutions to global warming as insurance policies in case we approach an environmental crisis This is from the NY Times.
Some recently funded space studies. One of which is : Roger Angel investigates the feasability of a 2000 kilometer solar shield at L1 to counter global warming (if global warming problems become serious enough to justify it this megascale intervention)
Wikipedia on global cooling
Wikipedia on global warming
Wikipedia on the global warming controversy