Arrheniuss Greenhouse

In 1898, Arrhenius put forward a theory we now call the greenhouse effect. A simplified explanation is that shortwave solar radiation can pass through the clear atmosphere relatively unimpeded, but longwave infrared radiation emitted by the warm surface of the Earth is absorbed partially and then re-emitted by a number of trace gases—particularly water vapor and carbon dioxide—in the cooler atmosphere above. On average, the outgoing infrared radiation balances the incoming solar radiation, so both the atmosphere and the surface will be warmer than they would be without the greenhouse gases. Using Stefan's Law (better known as the Stefan Boltzmann Law), Arrhenius formulated his greenhouse law. In its original form, it reads as follows: "if the quantity of carbonic acid increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression." This is still valid in the 1998 simplified expression by G. Myhre:

Arrhenius estimated that halving of CO2 would decrease temperatures by 7-9 degrees F (4-5 degrees C) and a doubling of CO2 would cause a temperature rise of 7-11 degrees F (5-6 degrees C). Although some of Arrhenius's calculations turned out to be wrong, current (2007) estimates from the Intergovernmental Panel on Climate Change (IPCC) say this value (the climate sensitivity) is likely to be between 3-8 degrees F (2-4.5 degrees C).

Nevertheless, over the decades after he developed this, Arrhenius's work was criticized, then reinforced, then criticized again. Many disregarded his conclusions, pointing to his simplification of the climate and how he failed to account for changes in cloud cover and humidity. The oceans would absorb any extra CO2 pumped into the atmosphere, and any remainder would be absorbed by plant life, leading to a lusher landscape, skeptics argued.

Until about 1960, most scientists dismissed the hothouse/greenhouse effect as implausible for the cause of ice ages, as Milutin Milankovitch had presented a mechanism using orbital changes of the earth (Milankovitch cycles) that has proven to be a powerful predictor of most of the millions of past climate changes. Today, the accepted explanation is that orbital forcing sets the timing for ice ages, with CO2 acting as an essential amplifying feedback.

Arrhenius was offered many opportunities to move to other European universities, and he delivered important lecture series at universities in the United States, but he always returned to Stockholm. He was elected as a foreign member of the Royal Society in 1911, was awarded the Society's Davy medal, and also the Faraday Medal of the Chemical Society (1914). Among the many tokens of distinction that he received were honorary degrees from the Universities of Birmingham, Cambridge, Edinburgh, Greifswald, Groningen, Heidelberg, Leipzig, and Oxford. In 1903, he received the Nobel Prize in chemistry, and in 1905, he was made director of the newly-created Nobel Institute for Physical Chemistry.

Nevertheless, Arrhenius was destined to have a bigger impact than he or anyone at that time could have imagined. Far beyond his mainstream work, he uncovered secrets of the Earth's atmosphere, inargu-ably becoming the father of climate change science. In doing so, he triggered research into what many see as the biggest threat to modern humans. Arrhenius was a contented man, happy in his work and family life. During World War I, he made successful efforts to release and repatriate German and Austrian scientists who had been prisoners of war. He was twice married—in 1894 to Sofia Rudbeck, by whom he had one son, and in 1905 to Maria Johansson, by whom he had one son and two daughters. He died at Stockholm on October 2, 1927.

sEE ALso: Global Warming; Greenhouse Effect; Greenhouse Gases.

BIBLIoGRAPHY. Svante August Arrhenius, "On the Influence of Carbonic Acid in the Air Upon the Temperature of the Ground', Philosophical Magazine (v.41, 1896); Svante August Arrhenius, Varldarnas utveckling (Worlds in the Making) (Harper & Bros., 1906/1908).

Ingrid Hartmann Independent Scholar

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