I will say it again:
Musk is not an engineer. E.g. he has not played Kerbel Space Program.
He demonstrably does not understand the tyranny of the rocket equation, and how obscenely uneconomical getting anything to, and doing anything in, space is: https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation
Geoengineering is something worth seriously discussing (and TBH I hope he draws attention to it), and "solar shades" are theoretically neat, but this is not the way. Not with the trajectory of launch tech we have.