Issues on Global Warming...

What proportion of global warming is attributable to humans?

I consider myself an environmentalist. I am concerned about the amount of pollution we generate, the animals we push to extinction, and the resources we exhaust. However, I don't believe that we are the driving force behind global warming. It concerns me that whenever we hear about the effects of global warming, it is always mixed with the message that we are irrevocably destroying the earth. It can hardly be disputed that the earth is warming and the percent of greenhouse gasses in the atmosphere is increasing. I would like to know, what evidence is there that humans are contributing to this significantly? The earth's temperature rises and falls cyclically, and it has been on the increase since before the industrial revolution. We currently are not near the highest temperature that we know the earth to have reached. The polar ice caps have melted several times before. So, what percentage of the current warming trend are due to humanity and what percentage is natural? Thanks, ERNIE M. AGUAN, BSED-GenSci, MAED A&S, w/ Ed.D Units What do you think?