Re: Whatever.
We who agree with the scientists and with some of the policymakers on this point think we have proof. Our reasons may not seem convincing to you but they are reasons, not assumptions. Have you looked at our reasons? Considered them in good faith?
(1) CO2 absorbs IR radiation. This goes back to John Tyndall and the 19th century. Pretty solidly established fact.
(2) The earth's heat balance involves sunlight in and IR out. To balance when the IR has to fight its way through a layer of CO2, the earth has to initially radiate more, at a higher temperature. This is pretty basic thermodynamics and it's confirmed by the fact that the moon, without any CO2 or water vapor to speak of, averages considerably colder than the earth.
(3) Atmospheric CO2 is increasing because of human fossil fuel use. This is pretty solid too. Who can pretend that we don't burn coal for electricity? Who can explain the rise in CO2 over the last century from about 300 parts per million to now near 400, as being a natural fluctuation?
(4) It's warmer than it was a century ago. This might be put down to natural events, but in view of 1, 2, and 3, it seems to us more likely to be our own doing.
(5) This is just a thumbnail sketch. For more details, go to realclimate.org or wikipedia.