The year is 1856. Eunice Foote, a physicist from Seneca Falls, New York, is about to conduct an experiment. She wants to measure the warming effect of sunlight on gases in Earth’s atmosphere.
Foote places glass cylinders filled with different gases in the sun and measures the temperature of each over time. She finds that certain gases absorb more heat than others and that carbon dioxide (CO2) gas traps the most heat—by far. From this, Foote comes to a groundbreaking conclusion. She proposes that a greater amount of carbon dioxide in the atmosphere would cause temperatures on Earth to rise.