Makes sense to me:
http://drezner.foreignpolicy.com/posts/2009/11/24/the_global_governance_of_apocalypses When the movies do it -- and here I'm thinking about Deep Impact, The Core, Children of Men, etc. -- there's usually a coterie of Really Smart People, or a Council of Elders, or some other expert-driven body that devises a risky but brilliant plan to solve the problem.
In the real world... well, I suspect the following would be true:
* There would be initial and profound disagreement among experts over what precisely to do;
* After a scientific consensus began to emerge, dissenters would go back to their home governments to lobby for political support
* There would be rampant suspicion of any multilateral effort by those asked to make an outsized contribution;
* The cost overruns... oh, the cost overruns;
* Conspiracy theories would pop up all over the friggin' place
* The plan wouldn't work.