">But assuming one could wave a wand and banish all CO2 from the atmosphere, it's unknown if this would significantly effect global temperatures.

It's pretty well known that if you cut the CO2 content to zero, it _would_ affect temperatures.

Using IPCC numbers, for example, you get a reduction of about 3 deg C to 7 deg C (out of a total greenhouse warming of 33 C, water vapor being the largest contributor)."

A 3 degree drop in average global temperature does not make an earth which is a "ice ball" though it would be a significant effect on global temperatures. A 3 degree drop gets us into a situation similar to Little Ice age- hardly what I think of as a "ice ball". So EVEN taking IPCC numbers we don't get a "ice ball". But I think relying on IPCC numbers is particularly a wise thing to do- afterall they are being directed by a fellow who gave us the "hockey stick". And UN is known to run organizations that rapes children- and puts nations engaging in trafficing in human being on "human right commissions". Not something that inspires much confidence for me.

But I don't say it wouldn't affect temperatures, I said it's "unknown if this would significantly effect global temperatures". You are saying that for each 100 ppm increase or decrease in CO2 it's affecting global temperature by 1 or more degrees. Though I might assume that could be right, I seen little to give me much confidence in this.

"Find me any credible citation that CO2 does not contribute to increasing the Earth's average surface temperature."

I think it pretty obvious at this point in time that CO2 levels don't cause ice ages- though I agree we have never had the low levels of CO2 that can achieved by waving a magic wand. It also obvious that CO2 levels are not responsible warm periods. I would accept that without any CO2 that Earth would on average be cooler- I'm not willing to say there would no affect, and if there was 1% or more CO2 this would be an even more significant factor.