Actually, as a physicist, I see no leap there. We know the absorption spectra of CO2. We measure an increase in the CO2 in the atmosphere. We measure the how we

Actually, as a physicist, I see no leap there. We know the absorption spectra of CO2. We measure an increase in the CO2 in the atmosphere. We measure the how well light penetrates the atmosphere, and we find it does so less well at the wavelengths that CO2 absorbs. At this point, we have a simple theory that is well supported by direct experimental evidence. What more do you need?