THE HOCKEY SCHTICK: Prof. Will Happer: Will increased carbon dioxide levels actually benefit planet?

Supposed ill effects of more CO2 are from flawed computer models in which water vapour and clouds multiply the modest direct warming by factors of up to 10

Did the world have just the right concentration of carbon dioxide at the pre-industrial level of 270 parts per million? Reading breathless media reports about CO2 "pollution" and about minimising our "carbon footprints", one might think that the earth cannot have too little CO2. Humans and most other animals would do fine in a world with no atmospheric CO2 - but most plants stop growing if CO2 levels drop much below 150 ppm, so we would starve to death without at least this minimal amount. We are probably better off with our current 390 ppm than with the preindustrial 270 ppm, and we would be better off with still more CO2. For example, there is evidence that California orange groves are about 30 percent more productive today than they were 150 years ago because of the increase of atmospheric CO2.

What atmospheric levels of CO2 would be a direct threat to health? Both the United States Navy and NASA have performed extensive studies of human tolerance to CO2. As a result of these studies, the navy recommends an upper limit of about 8,000 ppm for cruises of 90 days and NASA recommends an upper limit of 5,000 ppm for missions of 1,000 days. We conclude that atmospheric CO2 levels should be above about 150 ppm to avoid harming green plants and below about 5,000 ppm to avoid harming people.

That is a big range, and our atmosphere is much closer to the lower end than the upper end. We were not that far from CO2 anorexia when massive burning of fossil fuels began. At the current rate of burning fossil fuels, we are adding about 2 ppm of CO2 per year to the atmosphere, so getting from our current level of about 390 ppm to 1,000 ppm would take about 300 years—and 1,000 ppm is still less than most plants would prefer, and much less than either the NASA or the navy limit.

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William M. Briggs, Statistician » Logical Probability And The IPCC’s Ambiguous Forecasts

Thus, if A did not happen, the IPCC would point to its prediction and say, “See! We told you so. We said A was nearly impossible and it didn’t happen.” But if A did happen, it could say, “Well, A happened, it’s true. But it happens about 1 out of 4 times, which isn’t that unlikely. We can be satisfied with our prediction.”

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