I keep on saying that the “forcing” effects of CO2 are logarithmic while the cooling response of the planet rises exponentially. I’m not the only one saying this, serious heavy weight skeptics like Lindzen are saying the same thing. So what do these terms really mean? OK, a bit of background and then onto the pictures.
What is often quoted is that CO2 doubling causes an increase in radiance to earth’s surface of 3.7 watts/meter squared, which in turn raises temperatures about 1 degree Celsius. Why the reference to “doubling”? Because we’re talking about light and filtering materials. Consider that you have several pairs of sun glasses, each of which blocks 50% of the light. If you put two pairs in a row, do they block 100%? Of course not. The first pair blocks 50% and the second pair blocks 50% of what is left, which is 25% of the original light. The third pair would only block 12.5% of the original light. CO2 suffers from the same law of diminishing returns. What keeps getting left out of the climate discussion is what happens after the first doubling. The pre-industrial levels (1900 AD or so) of CO2 are commonly quoted at 278 PPM (parts per million) and the current levels are at about 385 ppm. If we look at this graph, it becomes pretty clear that we would have to generate a LOT of CO2 to get much more effect than we are already: Continue reading







