Yes I think that Biden truly thinks this is entirely possible.
Yes it might be a very affordable way of decreasing sunlight to the earth.
You put large tinfoil sheets in orbit of the planet. King of like starlink, if you put up enough of them it could work.
You don't have to blank out the sky just a tiny bit of it. It's expensive but there's no wind and no gravity, so something can be massive with only a minor support structure. I'm not saying it make sense now.
But it could be economical if you can get launch costs down to 100 grand per ton.
Granted it might just be easier to coat part of the sahara etc with like arrays of reflective material.