There is zero doubt in my mind that we are causing the planet to warm. It just makes sense, more people, more industry, more activity, things heat up. Think about when you are cooking in your house, or you have a few people over, it warms up inside.
What I don't know, and I don't even think the "experts" have a full grasp on is whether or not the global climate shift is going to be the death of us all.
I think the bigger concerns are over population, less natural resources, and the fact that emerging economies like China and India don't give two shits about the pollution they are creating so that we can have our nickle trinkets...