The main point is that the "tiny bit" of polution that humanity is causing could have some pretty major effects. We really don't know either way. A scenerio similar to the movie could in fact, happen, we don't know what the melt down point is. A simple drop of a degree or two more could signifigantly change the environment catastrophically. Or it might not.
However, I still think that what we're doing currently isn't helping the planet anyway. We're killing species off by the hundreds + yearly and making the place a little worse off for us to live. If you think the 2% (not sure if that's accurate or not) of CO2 that we're producing isn't going to make a difference, then by all means keep doing it. Just remember 2% is a heck of a lot more (in the global scheme of things) of C02 then before we came around.
