Svante August Arrhenius (19 February 1859 – 2 October 1927) was a Swedish scientist and one of the founders of the science of physical chemistry. He received the Nobel Prize for Chemistry in 1903.
Arrhenius developed a theory to explain the ice ages, and in 1896 he was the first scientist to attempt to calculate how changes in the levels of carbon dioxide in the atmosphere could alter the surface temperature through the greenhouse effect. Already in 1897, Arrhenius projected that fossil fuel combustion would increase carbon dioxide levels in the atmosphere, and estimated, by hand, that doubling CO2 would increase surface temperatures by between 5 and 6 degrees Centigrade. He used the infrared observations of the moon to calculate the absorption of infrared radiation by atmospheric CO2 and water vapour. Using Stefan Boltzmann law, he formulated his greenhouse law. In its original form, Arrhenius’ greenhouse law reads as follows:
If the quantity of carbonic acid [H2CO3] increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression.
Arrhenius’ absorption values for CO2 and his conclusions met criticism by Knut Ångström in 1900, who published the first modern infrared spectrum of CO2 with two absorption bands, and published experimental results that seemed to show that absorption of infrared radiation by the gas in the atmosphere was already “saturated” so that adding more could make no difference. Arrhenius replied strongly in 1901 (Annalen der Physik), dismissing the critique altogether. He touched the subject briefly in a technical book titled Lehrbuch der kosmischen Physik (1903). He later wrote Världarnas utveckling (1906) (English: Worlds in the Making) directed at a general audience, where he suggested that the human emission of CO2 would be strong enough to prevent the world from entering a new ice age, and that a warmer earth would be needed to feed the rapidly increasing population:
“To a certain extent the temperature of the earth’s surface, as we shall presently see, is conditioned by the properties of the atmosphere surrounding it, and particularly by the permeability of the latter for the rays of heat.” (p46)
“That the atmospheric envelopes limit the heat losses from the planets had been suggested about 1800 by the great French physicist Fourier. His ideas were further developed afterwards by Pouillet and Tyndall. Their theory has been styled the hot-house theory, because they thought that the atmosphere acted after the manner of the glass panes of hot-houses.” (p51)
“If the quantity of carbonic acid [CO2] in the air should sink to one-half its present percentage, the temperature would fall by about 4°; a diminution to one-quarter would reduce the temperature by 8°. On the other hand, any doubling of the percentage of carbon dioxide in the air would raise the temperature of the earth’s surface by 4°; and if the carbon dioxide were increased fourfold, the temperature would rise by 8°.” (p53)
“Although the sea, by absorbing carbonic acid, acts as a regulator of huge capacity, which takes up about five-sixths of the produced carbonic acid, we yet recognize that the slight percentage of carbonic acid in the atmosphere may by the advances of industry be changed to a noticeable degree in the course of a few centuries.” (p54)
“Since, now, warm ages have alternated with glacial periods, even after man appeared on the earth, we have to ask ourselves: Is it probable that we shall in the coming geological ages be visited by a new ice period that will drive us from our temperate countries into the hotter climates of Africa? There does not appear to be much ground for such an apprehension. The enormous combustion of coal by our industrial establishments suffices to increase the percentage of carbon dioxide in the air to a perceptible degree.” (p61)
“We often hear lamentations that the coal stored up in the earth is wasted by the present generation without any thought of the future, and we are terrified by the awful destruction of life and property which has followed the volcanic eruptions of our days. We may find a kind of consolation in the consideration that here, as in every other case, there is good mixed with the evil. By the influence of the increasing percentage of carbonic acid in the atmosphere, we may hope to enjoy ages with more equable and better climates, especially as regards the colder regions of the earth, ages when the earth will bring forth much more abundant crops than at present, for the benefit of rapidly propagating mankind.” (p63)
Arrhenius clearly believed that a warmer world would be a positive change. Most scientists dismissed the greenhouse effect as implausible for the cause of ice ages, as Serbian scientist Milutin Milanković had presented a mechanism using orbital changes of the earth (Milanković cycles). Nowadays, the accepted explanation is that orbital forcing sets the timing for ice ages with CO2 acting as an essential amplifying feedback.
The Arrhenius equation, lunar crater Arrhenius and the Arrhenius Labs at Stockholm University are named after him.