Geoscience Reference
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of East Anglia.
Callendar estimated that during the past half-century, “by fuel combustion Man
has added about 150,000 million tons of carbon dioxide to the air.” About three-
quarters of it had remained in the atmosphere; the rest the oceans had absorbed.
The atmospheric concentration of CO
2
had risen from 274 ppm in 1900 to between
289 and 310 ppm in 1936, he said. (A year later, he revised these figures to 280
ppm in 1900 and 300 ppm in 1936.)
