I hate being that person, but I have to honestly ask, if the scientific community as a whole cannot agree on exactly how much effect humans personally cause to the environment today, how can anyone claim with the level of surety that these people seem to have that something major is going to happen, that humans can mitigate, within a lifetime?
Public uncertainty does not prevent isolated individuals from getting science done. There's no reason to suspect that publicized uncertainty about global warming has anything to do with objective difficulty in obtaining solid evidence rather than its tendency to attract polemicists, cranks, and opinionated amateurs.
