I've become convince that scientists really don't have enough data to accurately assess man's influence on the global climate. Our planet has experienced several major climate shifts over its lifetime which are caused by an almost infinite number of variables that all intertwine and affect each other. There is simply no way for us to be able to discern what affect man is having on the global climate because we are just one of those variables.
I am note refuting the fact that the global climate is changing but for scientists to continue claiming that man is the major contributing factor to this change is not something I'm willing to buy into. Environmentalists should focus more on the negative affects pollution has on people in the short term and at the local level. Talking about global warming makes you look as ridiculous as The Day After Tomorrow. Talking about how the local coal plant or car emissions are causing an increase in major health problems gets people's attention and makes them more likely to side with you.
These major climate shifts happened over a very long period of time, while this is happening very quickly. Scientists have come a long way in understanding the variables which affect the climate and these are not idle claims. It's you who look ridiculous by denying something that is becoming universally accepted.