Climate Change

The Callendar effect: Here's how this man connected humans to global warming in 1938

Guy Callendar theorized that humans were unknowingly raising Earth’s temperature by burning fossil fuels in furnaces and factories. Image: UNSPLASH/Chris LeBoutillier

Sylvia G. Dee

Assistant Professor of Earth, Environmental and Planetary Sciences, Rice University

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A page from Guy Callendar’s 1938 paper shows how he tracked and calculated CO2 changes, all in his spare time. Image: GS Callendar

Callendar found global average temperatures that match with current estimates of the average temperatures of the time. Image: Ed Hawkins/Twitter

Guy Stewart Callendar in 1934. Image: G.S. Callendar Archive/University of East Anglia

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