The main cause of this is from the "green house effect". The greenhouse effect is caused by Bruning fossil fuels, gasoline, oil, coal and wood. This effect makes the heat that comes into earth cant get out beacuase of gasses that are surrounding the earth's atmosphere making the world increase in tempurature. The way to cure this problem is using the concept Reduce, Reuse & Recycle. The idea of this concept is using your things more than once, sorting the garbage you put in and using more fuel efficient cars.