What the work claims
Foote explicitly linked atmospheric CO2 concentration to climate warming. She claimed that gases with higher CO2 content would produce greater heating under solar exposure — and that this effect scaled with moisture content.
How it was done
Foote used an air pump, two glass cylinders, and four mercury-in-glass thermometers. She placed two thermometers in each cylinder and evacuated air from one while compressing it in the other. After both cylinders reached equal ambient temperatures, she exposed them to sunlight and measured temperature differences. She also tested shade versus sun, and dry versus moist air by dehydrating one cylinder and adding water to the other.
What holds up
CO2 reached 125 °F (52 °C) under sunlight — measurably hotter than air or hydrogen. The CO2-filled cylinder heated ‘very sensibly more’ and cooled ‘many times as long’ after removal from the Sun. Moisture content affected temperature results. These are all directly observed, recorded, and repeatable outcomes of her apparatus and protocol.
What does not
Her method could not isolate infrared absorption. She did not measure wavelength-specific absorption. She did not quantify CO2 concentration effects across gradients. She did not model or extrapolate to planetary scale. She did not establish a causal mechanism for greenhouse warming beyond solar heating of gas.
Why it matters beyond the lab
It matters because Foote identified CO2’s thermal dominance over other common gases in 1856 — decades before Tyndall’s widely cited infrared experiments — and grounded her claim in reproducible, quantitative observation. It repositions the origin of experimental climate physics away from sole attribution to male European scientists.
Is it worth your time
Yes — it is the earliest known experimental demonstration linking CO2 concentration to atmospheric heating, using direct measurement and controlled comparison. Its simplicity and clarity make it worth understanding as a foundational act of climate science.