Global warming Temperature changes Dust and dirt
Dust and dirt in the air come from natural sources such as volcanos, erosion and meteoric dust. People also add to it. Some of this dirt is large, so it falls out within a few hours. Some is so small that it could stay in the air for years. This big dirt is still very small. It's about the width of a human hair. The big dirt does not stay in the air for years though because rain hits it and brings it to the surface.