Eunice Foote and the 1856 Experiment That Found the Greenhouse Effect

In late August 1856, the American Association for the Advancement of Science held its annual meeting in Albany, New York. The country's leading men of science gathered to read papers on geology, astronomy and natural philosophy. On August 23, Joseph Henry, the secretary of the young Smithsonian Institution and probably the most respected physicist in the United States, rose to read a paper that was not his own. It was titled "Circumstances Affecting the Heat of the Sun's Rays," and its author was a woman named Eunice Newton Foote. She had placed thermometers inside glass cylinders filled with different gases, set them in the sun, and watched what happened. The cylinder filled with what she called carbonic acid gas, the substance we now call carbon dioxide, became the hottest of all, and it stayed hot longer after it was taken out of the sunlight. From that result she drew a conclusion that would take the rest of the world more than a century to absorb: an atmosphere with more of that gas would make the Earth warmer. Henry introduced the work with a few gracious remarks about science belonging to women as well as men. Then the paper, and the woman, all but disappeared from history.

In short: Eunice Foote, a scientist, inventor and women's rights activist, published experiments in 1856 showing that carbon dioxide absorbs heat from sunlight and suggesting that more of it in the air would warm the planet. The credit for discovering the greenhouse effect went for generations to the Irish physicist John Tyndall, whose more precise work came three years later. Her story is about science, and about who gets to be remembered for it.

A woman of Seneca Falls

Eunice Newton was born in 1819 in Goshen, Connecticut, and grew up in upstate New York. She studied at the Troy Female Seminary, the school Emma Willard founded to give young women an education in subjects, including science, that most schools reserved for men. Students there attended lectures in chemistry and biology at a nearby college. It was an unusual education, and it shows in her later work.

She married Elisha Foote, a lawyer and judge who was himself an amateur scientist and inventor and who later served as the U.S. commissioner of patents. The couple lived in Seneca Falls, New York, in the 1840s. In July 1848, when the first women's rights convention in American history met there, Eunice Foote was among the signers of the Declaration of Sentiments, the document that demanded equal rights for women, including the right to vote. She also served on the committee that prepared the convention's proceedings for publication.

That detail is worth carrying forward. The woman who discovered that carbon dioxide traps heat was also a woman who signed her name, at real social cost, to a demand that women be counted as full citizens. Eight years later, at a scientific meeting, she would not be the one to speak her own findings aloud.

The experiment in glass

Foote's apparatus was simple. She used two glass cylinders, each holding a thermometer. She could pump air out of one or compress it into the other, or fill them with different gases: dry air, moist air, hydrogen, carbon dioxide. She placed the cylinders side by side in sunlight and recorded the temperatures.

She found that moist air heated more than dry air, and that compressed air heated more than thin air. Above all, she found that the cylinder with carbon dioxide heated far more than the one with ordinary air and cooled more slowly afterward. The temperature differences were large enough to see easily.

She then made the leap. Her paper suggested that if the atmosphere held more carbon dioxide, the Earth would be warmer, and she speculated that the gas might help explain warmer periods in the planet's past. She had connected a laboratory measurement to the climate of the whole planet in a single sentence.

The paper appeared in the American Journal of Science and Arts later in 1856, one of the most important scientific journals in the country. Scientific American also wrote about her work that year, in a short article praising women who did science.

A scientific world with few doors open

The association that met in Albany in 1856 was only eight years old, and it was a different kind of institution than it is now. Its meetings mixed university professors with clergymen, physicians, surveyors and gentlemen naturalists, and anyone with a serious interest could take part. Even so, women were rare. The astronomer Maria Mitchell, who had discovered a comet in 1847 and won a medal from the king of Denmark for it, was elected to the association in 1850, the first woman to be admitted. A handful of others followed slowly.

There was no rule that said a woman could not stand and present her own paper. There did not need to be. Custom handled it. Respectable women were not expected to address mixed public audiences, a convention that women's rights activists of the same era were challenging at their own conventions, at real cost to their reputations. So a paper by a woman would typically be read aloud by a man, often a distinguished one, which lent it authority and at the same time made her a guest in her own work.

The published proceedings of the meeting tell part of the story. Elisha Foote's papers from the same meeting appeared in the association's official volume. Eunice's paper, as far as historians have been able to establish, did not. Her work survived because it ran in the American Journal of Science and Arts, and because one curious reader found it there more than 150 years later.

Then came Tyndall

In 1859, John Tyndall, working in London at the Royal Institution, began a series of experiments that would become famous. He built a more sophisticated instrument that measured how different gases absorbed radiant heat, what we would now call infrared radiation. He found that water vapor and carbon dioxide absorbed heat strongly while oxygen and nitrogen, the main components of air, were nearly transparent to it. Tyndall understood that this property of the atmosphere kept the Earth warm, and he explained the mechanism carefully.

For more than 150 years, textbooks credited Tyndall with discovering the physics behind the greenhouse effect. There is no clear evidence that he knew of Foote's work. Scientific communication across the Atlantic was slower and patchier than it is now, and a paper by an American woman, read by someone else at a regional meeting, was not likely to travel far.

What she found, and what she did not

Fairness to the history requires some precision, and the scientists who have studied Foote's paper have provided it. Her apparatus measured how gases heated when exposed to full sunlight, which includes visible and infrared light. The greenhouse effect, strictly, is about how gases absorb the infrared radiation that the Earth's warm surface gives off. Foote's experiment did not separate those effects, and some of what she observed may have come from other factors. Tyndall's work was more rigorous on exactly the question that matters for climate.

So it is too simple to say that Foote discovered everything and Tyndall stole the credit. A better summary is that Foote was the first person known to have shown experimentally that carbon dioxide absorbs heat and to have linked a higher level of it in the atmosphere to a warmer climate. Tyndall explained the physics more fully. Both deserve a place in the story. For generations, only one of them got it.

Foote also published a second paper, and she patented inventions, including improvements to shoe soles and to machinery. She kept working. She died in 1888, and her obituaries did not lead with her science.

The chain of discovery after her

Foote's experiment was the first link in a long chain, and following it forward shows how slowly ideas about climate grew and how firmly they were established long before modern politics touched them.

After Tyndall in 1859 came the Swedish chemist Svante Arrhenius, who in 1896 worked through tedious calculations by hand to estimate how much the Earth would warm if carbon dioxide in the air doubled. His answer, five to six degrees Celsius, ran higher than today's best estimates, but it was the right order of magnitude, worked out with a pencil a decade before the first airplane flew. Arrhenius expected the change to unfold over a very long time and thought a warmer climate might even be welcome in cold Sweden. In 1938, a British steam engineer named Guy Stewart Callendar gathered temperature records and carbon dioxide measurements and argued that the warming had already begun and that burning fossil fuels was the cause. Many experts dismissed him.

Then, in 1958, came the precise measurements on Mauna Loa that showed carbon dioxide rising year after year. By the late 1970s, the National Academy of Sciences was warning that doubling carbon dioxide would likely warm the planet by about three degrees Celsius, give or take. Every one of those steps rested on the same simple observation that Foote recorded with her thermometers. The jar of carbonic acid gas got hotter.

How she was found again

The rediscovery came from an unexpected direction. In 2010, a retired petroleum geologist named Ray Sorenson came across Foote's paper while reading old scientific journals and published an article about it in 2011. Historians of science picked up the thread. In the decade that followed, articles, a short film and conference talks brought her name back into circulation. Climate scientists now commonly mention her alongside Tyndall, and in 2026 she is much better known than she was in 2010.

It is a nice irony that an oil-industry geologist helped restore her name. Science is a commons. The record belongs to everyone, and sometimes the person who reads the old journal closely is not the one you would expect.

Why she was forgotten

Several reasons stack up. She was an amateur, without a university post or a laboratory staff, at a time when science was professionalizing. She published little. She did not present her own work, and the man who read it was so prominent that he could easily seem the important figure in the room. And she was a woman, at a time when women were excluded from most universities, most scientific societies and the vote.

Her case is not unusual. The history of science is full of women whose work was credited to colleagues, husbands or supervisors, a pattern the historian Margaret Rossiter named the Matilda effect. The pattern matters beyond fairness. When we lose track of who found what, we lose a sense of how long we have known it. The basic physics that links carbon dioxide to warming has been on the record since before the Civil War. Every argument since then about whether burning fossil fuels warms the planet has been, in a sense, an argument with a woman in a sunlit room in New York.

What her story means for the climate fight

Here is the argument we would make. The climate debate is sometimes framed as a new and uncertain science, with the implication that it is reasonable to wait for more evidence. Foote's story is a corrective. The basic science is old, simple and confirmed many times over. What has been missing is not knowledge but the political will to act on it, and the power to overcome the industries that profit from delay.

People who are skeptical of climate policy often raise legitimate questions about costs: what higher energy prices mean for working families, rural communities and industrial jobs. Those are real concerns, and good climate policy has to answer them, with help for workers and regions that depend on fossil fuels, and clean energy that is cheaper rather than more expensive. But the question of whether carbon dioxide warms the planet is not one of them. That was answered in 1856.

And her story is a reminder of who gets left out of the room. Climate change hits hardest the people least likely to be in the hearing room or on the scientific panel: frontline communities, poor countries, workers outdoors in the heat, and the young. Foote signed the Declaration of Sentiments because she believed women belonged in public life. The climate movement is at its best when it remembers that everyone affected deserves a voice.

What you can do

• Watch the line she predicted. The climate data page shows carbon dioxide measured at Mauna Loa, the global temperature record, the U.S. power mix and clean power by state. The numbers she would have wanted to see are there.
• Teach her name. If you are a teacher, a parent or a scout leader, Foote's experiment can be recreated with jars, thermometers and a lamp or a sunny window. It is a vivid way to show a child that the science is simple.
• Find a local group. Environmental and science-education nonprofits in your state are listed in our directory of organizations by cause. Many welcome volunteers who are not scientists.
• Keep up with climate policy. Our page on climate policy follows what Congress, the states and the courts are doing with the science we have had since 1856.