text: Humans are a very small cost of global warming.  Anthropogenic greenhouse gases in the atmosphere only account for 4% of all greenhouse gases.  If you look at graphs scientists make up of the temperature over the past 100,000,000 years you can see that we are just at another warm period in our earths history.  There has been warmer times before.  I don't really know how the scientists can figure out what the temperature was 100,000,000 years ago but i have a graph in my environmental science text book that shows that they have.