Does it really matter who or what is causing global warming, whether it is being sped up or not, or if it has occured before? It is happening, and can have serious financial, economical, and health problems for future generations.
If you wish, give me one week, and I will come up with 5 real scientific papers to back up my points. It isn't hard to do, I do it for school all the time.
The earth warms and cools. There is no reason it cannot be a new trend if it takes 1/1000th the normal amount of time to raise one degree (celcius). But if it's man made or not, it will seriously affect man, and man's environment. So take charge of the earth and don't let it happen!