The asteroid NASA found enters our atmosphere and triggers a completely unforeseeable reaction upon reaching earth: it ignites the pollution, methane, and smog/particulate matter we've been spewing into the atmosphere for 150+ years. Climate change occurs over night as the atmosphere smolders. Ceasefires in conflict zones are called indefinitely. Intensive mining and resource extraction halts. After a few weeks/months, all the combustible pollution is gone, along with a sizable portion of the breathable atmosphere. People are forced to stay inside and generally limit their movements, finally allowing covid (and quite a few other communicable diseases) to burn itself out. Mutual aid networks and locally produced goods and services become the norm for supply networks. Surviving farm animals break free of their captivity and domesticated genetic breeding. New habitats form where they were previously leveled for golf courses and parking lots. Life resumes, quieter, safer, and more peaceful. Humanity is, at long last, humbled.