I've been thinking about this claim: The effectiveness of green-houses and cold-frames has been known since medieval times. And Wickipedia tells us that in th

I've been thinking about this claim: The effectiveness of green-houses and cold-frames has been known since medieval times. And Wickipedia tells us that in the 1920's Joseph Fourier proposed that the "greenhouse effect" is responsible for the warming of the earth. At any time after that, the amount of heating which would come from increased levels of CO2 (and other gasses) could have been directly calculated. So none of this is at all controversial to atmospheric scientists. About the only "unknown" was just how quickly our use of fossil fuels would alter the earths atmosphere. However the actual level of CO2 in the atmosphere has been tracked since 1958 at the Mauna Loa Volcanic Observatory.