G. S. Callendar

In the first half of the twentieth century, the carbon dioxide theory of climate change had fallen out of favour with climatologists. Beginning in 1938, Guy Stewart Callendar (1898-1964), a noted steam engineer and amateur meteorologist, revived this theory by arguing that rising global temperatures and increased coal burning were closely linked. Working from his home in West Sussex, England, Callendar collected weather data from frontier stations around the world, formulated a coherent theory of infrared absorption by trace gases, and demonstrated that the carbon dioxide content of the atmosphere, like the temperature, was indeed rising.

Noting an upward trend in temperatures for the first four decades of the twentieth century, Callendar combined these results with studies of the retreat of glaciers, measurements of rising concentrations of atmospheric carbon dioxide since pre-industrial times, and information newly available concerning the infrared absorption bands of atmospheric constituents. He concluded that the trend toward higher temperatures was significant, especially north of the forty-fifth parallel; that increased use of fossil fuels had caused a rise of the concentration of carbon dioxide in the atmosphere of about ten percent from nineteenth century levels; and that increased sky radiation from the extra carbon dioxide was linked to the rising temperature trend.

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