Carbon and solar radiation
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Since antiquity, astronomers have identified three motions of the Earth: rotation (the daily cycle), revolution (the annual cycle), and the precession of the equinoxes (a cycle of twenty-five thousand years). The temperature changes associated with the first two cycles are obvious. Scholars, including the French mathematician Joseph-Alphonse Adhémar (1797–1862), developed a theory to explain the third, the astronomical cycle. But the existence of glacial periods was not confirmed until the 1970s. Ice caps affect the climate because of their very high albedo (reflectivity).
Conversely, the climate (through its thermal influence) alters the extent of the ice caps. The greenhouse effect was already known in the 19th century. In 1896, Svante Arrhenius, a Swedish chemist, was the first to confirm that air rich in CO2 (carbon dioxide) retains more heat from solar radiation, causing air temperatures to rise. Changes in the carbon cycle can explain major climatic variations. Ultimately, a decrease in CO2 concentration may have caused the glacial periods.
Can the two theories be reconciled to link the ice caps, the climate, and atmospheric CO2? Glacial periods may result from the internal oscillation of a coupled system…
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Global warming: the origins of a public issue
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