This is where people who think space access is only for satellites and LEO space stations have no imagination. We’re at a place now where if global warming did suddenly start to run away, within a year, we could realistically launch enough solar shades to meaningfully impact the situation. It’s far fetched, but this is why innovation in general is important. Not for what we know now, but for all the unknown ways it could be used in the future.
Right now we're still not close to that kind of capacity.
I suspect just painting all the rooftops and tarmac white will be about as effective as 2000 Starship launches filled with mylar sheets, plus an L1 delivery system because one thing you really don't want for a global warming mitigation is for them to fall out of LEO and burn up almost immediately from the huge drag-to-inertia ratio.