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Monte Heil (Daily Bee, March 31, 2019) claims that it is a “scientifically proven fact” that atmospheric CO2 cannot reach life-threatening concentrations because “our earth is not surrounded by a retaining wall or bubble.” He appears to be arguing that any CO2 in excess of a concentration favorable to life will by some unspecified mechanism automatically off-gas into outer space. He makes this argument despite the fact that there is strong evidence CO2 levels have exceeded this limit multiple times in the past. It would be informative if Mr. Heil would provide a source for what he calls a “proven fact.”

The science I am familiar with shows that, in order for a gas molecule to diffuse into space from the atmosphere, it must overcome the downward force of gravity. That science also shows that, due to the mass of the CO2 molecule, it does not normally reach sufficient escape velocity to overcome that force. This explains why the CO2 humans are now producing from burning fossil fuels is accumulating in the atmosphere. (Search for “Why wouldn’t Earth’s atmosphere escape into space? Quora”)

The concentration of CO2 in the atmosphere is now approximately 410 ppm. (It was 280 ppm before the Industrial Revolution.) At the current rate of production of human-caused emissions, the concentration will reach some 500 ppm within the next 50 years. Mainstream climate scientists agree that, at that level, the consequences will be disruptive to many ecosystems. (Search for “How the World Passed a Carbon Threshold and Why It Matters.”)

JACK DeBAUN

Sandpoint