Which American scientist showed in 1856 that carbon dioxide warmed more in sunlight?

Eunice Newton Foote showed in 1856 that carbon dioxide warmed more in sunlight. Her experiment made her an early pioneer of climate science and the study of what is now called the greenhouse effect.

Foote placed gases, including ordinary air, hydrogen, and carbon dioxide, in glass cylinders fitted with thermometers. After exposing them to sunlight, she found that carbon dioxide reached a higher temperature and retained heat longer than the other gases. She referred to carbon dioxide by its older name, “carbonic acid gas.”

Foote presented her findings at the 1856 meeting of the American Association for the Advancement of Science. Because women had limited opportunities to present research publicly, Joseph Henry of the Smithsonian read her paper. Her conclusion anticipated the modern idea that changes in atmospheric carbon dioxide can influence Earth’s temperature.

A common mix-up credits John Tyndall alone with discovering the greenhouse effect. Tyndall’s 1859 work was more detailed and helped explain infrared absorption, but Foote’s 1856 experiment came first. Her work was largely overlooked until historians revisited it in the twenty-first century.