>>142438291. There is no current feasible way to launch a plate that large in any form save piece by piece to be assembled in space, which would take an inordinate amount of time and resources.
2. Given the above, there are (relatively) easier ways to carry out the scheme you're proposing. One of them is pumping radiation-reflecting aerosols into the atmosphere, which is essentially what geoengineers are proposing as a potential short-term solution to global-warming. Given how urgent that threat is to humanity's survival, I think you'd actually become a saviour instead of a supervillain.
https://www.nytimes.com/2021/03/25/climate/geoengineering-sunlight.html 
