While denial of global warming is without a doubt from bandwagon appeal furthered by campaign donations, I get the impression that the acceptance of global warming by politicians is also primarily a result of the bandwagon effect. The bandwagon fallacy being
[An argumentum ad populum] that concludes that a proposition is true because many or most people believe it: "If many believe so, it is so."
The main reason I think so is because it is not a major issue for most of them. I get the impression that if they knew how serious it is, then it would be a major issue for them, and they would have made more efforts to combat it.