A large number of our governance problems are due to the childish attitude to governance held by so many, especially those on the left.

it's worth pointing out here how big the mismatch is between how movies think end-of-the-world global governance looks like as compared to what would happen in the real world.

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...

In the real world there are no Really Smart People or any other experienced or qualified groups that could devise some workable plan. This type of thinking is a vestige of early childhood when some adult or parent really was your only hope, and really did have seemingly vast power. This phase should pass long before puberty, but for some in the extended childhood of institutional life it sometimes lasts longer or they relapse, regress to childish views.

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.

... Unless the End of the World matched perfectly onto a pre-existing international organization, my hunch is that the great powers would start up something de novo.

Never waste a crisis. The purpose of a crisis is to enable greedy people to elevate themselves, though it only pays off if it isn't really the end-of-the-world.