The Part-Time Climate Scientist

O n a Wednesday in February 1938, Guy Stewart Callendar—a rangy, soft-spoken steam engineer, who had turned 40 just the week before—stood before a group of leading scientists, members of the United Kingdom’s Royal Meteorological Society. He had a bold idea to share: Humans’ burning of fuel was making the planet warmer.

By Callendar’s calculations, over the past half century, humanity had added 150 billion tons of CO2 to the atmosphere, raising the average global temperature about 0.03 degrees Celsius per decade—a trend, he noted, that could accelerate.

Callendar, an engineer whose day job was concerned with steam engines and turbines, knew he was going up against mainstream scientific wisdom. As he wrote at the very beginning of the paper detailing his findings, he was well aware that few scientists “would be prepared to admit that the activities of man could have any influence upon phenomena of so vast a scale.”1 But calmly, methodically, he proceeded.

Sure enough, Callendar’s presentation immediately met skepticism. Sir George Simpson, a prominent scientist soon to head the Royal Meteorological Society, dismissed the proposed link between rising CO2 levels and temperature as “rather a coincidence.” He also implied that a non-expert could not possibly understand atmospheric processes well enough to calculate the effects of solar radiation which Callendar had asserted was being absorbed in greater quantities by increased CO2 in the atmosphere. Others pointed to alleged shortcomings such as the supposed unreliability of Callendar’s data.

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