This is a quickie for curiousnc, obviously an alias, that wonders how to confront the more devout minions of the Great and Powerful Carbon. First, there is nothing "anti" science about being skeptical. There is actually more that is "anti" science about being a naive believer of everything "science" like it is some replacement for a lost divinity. Scientists are people and every very smart people screw up.
You will notice that the dT(CO2) 1 C per doubling of CO2 equivalent concentration just hits the peaks of the various "surface" temperatures. Looking at the impact this way you would not be including volcanic, solar and other possible "cooling" impacts that could impact your estimate.
That is why some are skeptical.