Where this discovery comes from
Carbon dioxide in the air
In 1856 the American scientist Eunice Foote filled two glass cylinders, one with ordinary air and one with carbon dioxide, and set them in the sun with a thermometer in each. The one with carbon dioxide got hotter, and stayed hot longer once it was taken out of the sun.
One thing to hold: Two glass jars, two thermometers, and a sunny window.
Why it matters: She wrote that more of this gas in the air would make the Earth warmer. In March 1958 Charles David Keeling began measuring it on Mauna Loa in Hawaii: 313 parts per million. The same instrument record now reads over 420.
What we don’t know: Foote did not explain why the gas held heat; John Tyndall measured that a few years later. Her paper was read at a science meeting by a man, Joseph Henry, and was little known for a long time afterwards.
Dates:
- 1856 Eunice Foote’s two glass cylinders.
- 1958 Keeling’s first Mauna Loa reading: 313 ppm.
- 2013 The Mauna Loa record passes 400 ppm.