I can not help but think back to the scientist who sid Mt St. Helens eruption put out more CO2 than all of humakind ever did. That happened over a couple days, right? Well, look at what Vesuvius did in 1944, or the eruption in the Phillipines, or the multitude of other volcanos that are constantly erupting.
Having that evidence glaring at me, I am left to conclude that the human population can effect the environment to a point short of themro nuclear war, but the Earth itself can do far more damage than we could ever hope to.
In conclusion, I think Skuzzy put it best when he said that no one here on Earth understands all the factors that are a part of climatology. They will never fully be understood, until it is too late. By then, we will probably realise that all the rediculous paper work and bad will generated by ploitics were the biggest problem for the planet.