Surprised? Scientists knew about Greenhouse gases long ago

imgresIt was fascinating to learn that the concept of “global warming” (or cooling) by the presence (or absence) of certain gases in our atmosphere was discovered about two hundred years ago, as discussed in a recent article in Distillations, the magazine of the Chemical Heritage Foundation. This is how scientists came to this knowledge.

Joseph Fourier, best known for his mathematical genius, made calculations to try and determine what set the temperature of the earth. He balanced the energy coming from the sun against the outgoing energy (in infrared form) and concluded that the average earth’s temperature should be around zero degrees Fahrenheit. He didn’t know or understand about the effect of atmospheric gases trapping infrared radiation. Another French scientist, Claude Pouilet speculated that water vapor and carbon dioxide might act to do this. A British scientist, John Tyndall  in 1859 set up an experiment to measure the amount of radiant heat absorbed by various gases. He demonstrated that oxygen, nitrogen and hydrogen are transparent to infrared radiation, while water vapor, carbon dioxide, and methane absorbed such radiation. Tyndall speculated, perhaps concluded, that aqueous water vapor was responsible for the higher-than calculated (by Fourier) earth temperature and therefore created the beneficial climate of our planet.

Several decades later Arrhenius thought about this and continued Fourier’s calculations, now also thinking about carbon dioxide. He recognized that the amount of water vapor in the air varies substantially with the seasons, while the amount of carbon dioxide is relatively constant, though very slowly increasing. He calculated that a doubling of carbon dioxide could increase the earth’s temperature 11-14 degrees F. (This remarkably close to current models which postulate a 5.5 to 9 degrees F  increase for a doubling of CO2) .He also concluded that historical ice ages could have come about due to a large decrease in atmospheric CO2.

Living in a cold climate, Arrhenius did not worry about a possible rise in the earth’s temperature. In fact, he suggested that an increase in atmospheric CO2 would beneficially affect the colder regions of the earth, bringing about more abundant  crops, etc.

So, it seems that the scientific community has long been aware of the effect of Greenhouse gases. But there was more concern about the possibility of another ice age than about the melting of glaciers and the rise of ocean levels. This is now our problem.

 

 

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