http://earthobservatory.nasa.gov/Library/Giants/Arrhenius/ A hundred years ago, Swedish scientist Svante Arrhenius asked the important question “Is the mean temperature of the ground in any way influenced by the presence of the heat-absorbing gases in the atmosphere?” He went on to become the first person to investigate the effect that doubling atmospheric carbon dioxide would have on global climate. The question was debated throughout the early part of the 20th century and is still a main concern of Earth scientists today. Ironically, Arrhenius’ education and training were not in climate research, but rather electrochemistry. His doctoral thesis on the chemical theory of electrolytes in 1884 was initially regarded as mediocre by his examination committee, but later was heralded as an important work regarding the theory of affinity. In 1891, Arrhenius was a founder and the first secretary of the Stockholm Physical Society, a group of scientists whose interests included geology, meteorology, and astronomy. His association with this society would later help stimulate his interests in cosmic physics—the physics of the Earth, sea, and atmosphere. In 1903, Arrhenius was awarded the Nobel Prize for Chemistry for his work on the electrolytic theory of dissociation. In the years following his international recognition, Arrhenius lectured throughout Europe and was elected to numerous scientific societies. Arrhenius did very little research in the fields of climatology and geophysics, and considered any work in these fields a hobby. His basic approach was to apply knowledge of basic scientific principles to make sense of existing observations, while hypothesizing a theory on the cause of the “ Ice Age.” Later on, his geophysical work would serve as a catalyst for the work of others. In 1895, Arrhenius presented a paper to the Stockholm Physical Society titled, “On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground.” This article described an energy budget model that considered the radiative effects of carbon dioxide (carbonic acid) and water vapor on the surface temperature of the Earth, and variations in atmospheric carbon dioxide concentrations. In order to proceed with his experiments, Arrhenius relied heavily on the experiments and observations of other scientists, including Josef Stefan, Arvid Gustaf Högbom, Samuel Langley, Leon Teisserenc de Bort, Knut Angstrom, Alexander Buchan, Luigi De Marchi, Joseph Fourier, C.S.M. Pouillet, and John Tyndall. Arrhenius argued that variations in trace constituents—namely carbon dioxide —of the atmosphere could greatly influence the heat budget of the Earth. Using the best data available to him (and making many assumptions and estimates that were necessary), he performed a series of calculations on the temperature effects of increasing and decreasing amounts of carbon dioxide in the Earth's atmosphere. His calculations showed that the “temperature of the Arctic regions would rise about 8 degrees or 9 degrees Celsius, if the carbonic acid increased 2.5 to 3 times its present value. In order to get the temperature of the ice age between the 40th and 50th parallels, the carbonic acid in the air should sink to 0.62 to 0.55 of present value (lowering the temperature 4 degrees to 5 degrees Celsius).” During the next ten years, Arrhenius continued his work on the effects of carbon dioxide on climate, and published a two-volume technical book titled Lehrbuch der kosmischen Physik in 1903; but this work was not widely read, as it was a textbook for a discipline that did not yet exist. A few years later, Arrhenius published Worlds in the Making, a non-technical book that reached a greater audience. In this book Arrhenius first describes the “hot-house theory ”of the atmosphere, stating that the Earth's temperature is about 30 degrees warmer than it would be due to the“ heat-protection action of gases contained in the atmosphere,”a theory based on ideas developed by Fourier, Pouillet, and (especially) Tyndall. His calculations demonstrated that if the atmosphere had no carbon dioxide, the surface temperature of the Earth would fall about 21 degrees Celsius, and that this cooler atmosphere would contain less water vapor, resulting in an additional temperature decrease of approximately 10 degrees Celsius. It is important to note that Arrhenius was not very concerned with rising carbon dioxide levels at the time, but rather was attempting to find an explanation for high latitude temperature changes that could be attributed to the onset of the ice ages and interglacial periods. By 1904, Arrhenius became concerned with rapid increases in anthropogenic carbon emissions and recognized 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.” He eventually made the suggestion that an increase in atmospheric carbon dioxide due to the burning of fossil fuels could be beneficial, making the Earth's climates “more equable,” stimulating plant growth, and providing more food for a larger population. This view differs radically from current concerns over the harmful effects of a global warming caused by industrial emissions and deforestation. Until about 1960, most scientists dismissed the notion as implausible that humans could significantly affect average global temperatures. Today, however, we know that carbon dioxide levels have risen about 25 percent—a rate much faster than Arrhenius first predicted—and average global temperatures have risen about 0.5 degrees Celsius. --

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