In the 19th century great scientists such as John Tyndall and Svante Arrhenius anticipated greenhouse theory, arguing (in Tyndall’s words) that “rays from the sun and fixed stars could reach the earth through the atmosphere more easily than the rays emanating from the earth could get back into space” (1863) and that concentrations of CO2 could trigger feedbacks that would account for rising global temperatures (Arrhenius 1896). This in fact became conventional wisdom until critics in the early 20th century suggested other factors to explain climate change than human production of CO2. The critics included T. C. Chamberlin who pointed to changes in oceans as a key cause, Knut Angstrom, Charles Greely Abbott and F. E. Fowle who believed water vapour would absorb infrared radiation. By 1929 G. C. Simpson was able to say confidently that CO2 could have no real effect on climate. This became the orthodoxy until Guy Callendar strongly challenged it in 1939.

[source: Fleming, Callendar Effect ]

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