Very, very (too much repetition of that space-taking 'filler' word but, I think, needed in this instance) very bad idea. It would be a huge mistake to 'block' any amount of sunlight that now reaches the atmosphere, just to 'help' offset global warming. No one one can predict the outcome of doing that just as no one, 150 years ago, could've predicted the outcome of burning fossil fuels that got us into our current predicament. There are much better ways to deal with the life-threatening issue of global warming in what is a long-term geologic cooling period, just not the political will to take those necessary steps.

Eureka! Let's just block some of the sunlight (not even a large contributor to atmospheric warming) and allow fossil fuel usage to continue to dump more greenhouse gases into the atmosphere and problem solved. Which would be the inevitable outcome, as long as 'dark money', i.e. lobbyists, continue the stranglehold big oil has on Politian's. Even the idea of spraying reflective particles into the stratosphere, which has been suggested, is nothing less than inviting disaster. We've already done terrible things to the atmosphere and it would be stupid to do another terrible thing to mitigate the terrible thing we've already done. As is said, two wrongs don't, and never will, make a right.