I would encourage you to look at the IPCC graph of greenhouse gases and when the increse started. It started to increase dramaticly during the industrial revolution started. Also they give a computer simulation of human imposed greenhouse gases, natural greenhouse gases, and both. the Computer came very close to the actual graph of green house gases when both were calculated together.
Unfortunately, we are the cause. Our population growth in the last 100 years is astonishing. Our planet can only take care of 9.6 billion people. We are over 6 billion right now. When Kennedy was inaguarated we were at 3 billion.
I linked a video many posts back…check it out. Even if you don’t believe in global warming. He gives a very good argument.