The negrosphere is a sub-category of the troposphere. Lying approximately ten to twelve feet above the ground level. The negrosphere was formed when blacks began smoking weed, in the early 1420's. The make-up of the negrosphere changes depending on your locale, and the illegal substances exhaled in your region. The negrosphere also has an interesting effect over parts of southern California, where it mixes with the intense amount of Coor's mist - Which is itself a bi-product of brodom. This effect known as the Negroe-Coor's effect (or NCE for short) is what caused the great earthquake and subsequent separation of California from the continent of North America in 2002.
Dude. Mike went too high into the negrosphere when he jumped his dirtbike. He's now permafaded... and half black.
Scientists have recently confirmed that the reason heat rises in a house is caused when certain gases become trapped in the negrosphere and cause a positively charged reaction, similar to that of cashing a bowl.