Space debris is science biggest mistake contributed to mankind?

Ok, first things first, some scientists have proposed sending many tiny objects (pieces of metal and the like) far outside of earths atmosphere to block the sun some to slow down global warming. This makes the idea of space junk harming the climate absurd. The junk has to be out of low-earth orbit to stay up there for more than a few months. Sputnik 1&2 fell back to earth decades ago. Aside from these facts, how in the world is some paint chips and fuel salauge warm up a celetial body thousands of miles across. The whole idea is absurd.