Last April on Radio Ecoshock (links below) they broadcast a very very interesting interview with Nate Lewis about climate change issues. Especially he talked about honest science regarding carbon & global warming ..
Among the things he said ... repeating as well as I can ... It doesn't take a rocket scientist to recognize that when you burn oil, that the carbon in the oil goes somewhere.
It's well known science the amount of CO2 (and other gasses) that are emitted from a car burning gasoline or other ways of burning oil. e.g. the 'smog check' methods are one way of showing what gasses are emitted by burning gasoline.
It's also well known how much oil (gasoline etc) is being burned across the country and to some extent it's well known how much is being burned worldwide.
It's also known how much carbon (and other gasses) are building up in the atmosphere.
It's also known that the carbon buildup matches the amount of oil being burned.
Therefore the carbon buildup is directly attributable to human activity.. not cows farting, not volcanos, but to humans burning fossil fuel oil.
He did admit it's not a 100% proved thing that the carbon buildup absolutely will cause a warming of the environment. He did point out that with 700,000 yrs of data (e.g. from ice core data) it's well known that every time CO2 concentration was high in the atmosphere it was matched by high temperatures on the planet. And that the CO2 levels we're heading towards are much higher than any recorded time in that 700,000 yrs.