Do we really know what's going on? (Score 1)

Everyone claims that global warming IS happening because of what's happened in the past 20-30 years. Can we claim that we know everything from those 30 yrs? It's pretty arrogant if you think that you know exactly what's going on with the earth from 30 yrs considering that the earth has a 4.5 billion year history. All I know is that the weather has been getting warmer over the years.