The two warmest years the Earth has had were in 1990 and 1991, because each year about 20 tons of carbon dioxide entered the atmosphere. And the reason that the two warmest years occured in 1990 and 1991 was because the strong effects of El Nino and La Nina happen every thousand years. America's cars and trucks produce 20 percent of United States carbon dioxide emissions. Carbon Dioxide emission is the primary global warming pollutant and the problem is getting worse. As they guzzle gas, these vehicles serve as personal global warming machines, polluting our children's air and threatening the enviroment.
Aerosol particles are like hair spray or other aerosol products.
According to one authority, it now amounts to about fifty million tons annually and is about ten to twenty percent of all atmospheric aerosols. Scientist believe that aerosol particles have recently cooled the Northern Hemisphere by about 0.5 degrees Celsius, thus counteracting the rise in temperature caused by carbon dioxide. While other scientist don't rule out the possibility that they have recently had a warming effect at the surface in the same area.