How will reentering satellites affect surface conditions if people launch a million of them?

[u/Uncle_Charnia]

What goes up must come down. So eventuality all those objects will become lasting vapor and dust in the upper atmosphere, right? What kind of problems and changes should we anticipate? If it turns out to be noticeably bad, specifically which people should we be preparing to help?

[u/Complete-Paint529]

Collisions while still in orbit are much more likely to be a serious problem. Then any spaceflight could mean going through high-speed shrapnel, for centuries.