You need to write an essay on global warming. Well, first in an essay like this you have to give numbers and facts. That’s why you have to do a big research before starting to write something. Let me give you some information about the global warming. The IPCC stated that for the last century the Earth was warmed by 0.74C. Of course, this is not the exact information, because most of the US stations are unable to fix the exact Earth temperature. What affects it? Probably humans, you can note that in your essay or dissertation. By the last centuries humans were affecting more harm to the planet than the sun radiation.