Sure, I'll take a crack at the first one, involving 'a few' Falcon Heavy launches. Falcon Heavy can get (very roughly) 16 tonnes to L1. Ignoring critical station-keeping and rigidity issues entirely for the sake of simplicity, and assuming the sail is a single sheet of aluminized mylar at 10 g/m^2, that's 1.6 square kilometers of coverage. To put the planet in shadow would require about 100 million such shades.
More importantly, people who won't do anything about the problem now while it's getting worse will not do anything if we had a temporary fix in place. This should be obvious from human nature, if it's not obvious, you can observe those temporary fixes permanently installed as infrastructure and business operations all over. We don't need more time to think about it, we just need to get started.
More importantly, people who won't do anything about the problem now while it's getting worse will not do anything if we had a temporary fix in place. This should be obvious from human nature, if it's not obvious, you can observe those temporary fixes permanently installed as infrastructure and business operations all over. We don't need more time to think about it, we just need to get started.