A climate change tutorial – why there is no existential threat

 Here is a link to to a paper by Howard Hayden, Emeritus Professor of Physics, University of Connecticut, titled "CO2 and Climate: A Tutorial.

It does not appear that CO2 is an existential threat.

Here are some excepts from the paper.

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At higher CO2 concentrations, adding more CO2 does little to increase the greenhouse effect, for the simple reason that most (not all) of the IR that CO2 can absorb is already absorbed. (The equivalent phenomenon in economics is called diminishing returns.) In fact, the current discussion among climate scientists is about how much greenhouse effect there would be if the increase in CO2 concentration were 400 parts per million (i.e., the concentration would be doubled from 400 to 800). The temperature rise due to a doubling of CO2 concentration (with all that entails) is lovingly called the sensitivity to doubling. A second doubling (from 800 ppmv to 1,600 ppmv) would cause the same temperature rise.

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A doubling of CO2 concentration—adding as much CO2 as we presently have, from our present 400 ppmv to 800 ppmv—would increase the blocking from 150 W/m2 to 153.5 W/m2. The “forcing” would cause the surface temperature to rise—all other things being equal— by 0.65 ºC (1.1 ºF). Well, that needs be corrected to account for the fact that 20% of the enhanced IR will be blocked. We add 25% to the 3.5 W/m2, and get 4.375 W/m2, with a corresponding temperature rise of 0.8 ºC (1.4 ºF). In other words, the warming that would be caused by the next 400 ppmv would be about one-tenth as much as caused by the first 400 ppmv.