Eunice Newton Foote

An amateur scientist, Foote conducted a series of experiments that demonstrated the interactions of sunlight on different gases.[1] She used an air pump, four mercury-in-glass thermometers, and two glass cylinders. She placed two thermometers in each cylinder, then by using the air pump, she evacuated the air from one cylinder and compressed it in the other. Allowing both cylinders to reach the same temperature, she placed the cylinders in the sunlight to measure temperature variance once heated and under different moisture conditions. She performed this experiment on carbon dioxide (CO₂), air, and hydrogen.[10]

Eunice Foote - "Circumstances Affecting the Heat of the Sun's Rays" (1856), American Journal of Science and Arts

Of the gases she tested, Foote discovered that CO₂ trapped the most heat, reaching a temperature of 125 °F (52 °C). She concluded: "The receiver containing this gas became itself much heated—very sensibly more so than the other—and on being removed [from the Sun], it was many times as long in cooling.[1] Looking to the history of the Earth, Foote theorized that "An atmosphere of that gas would give to our earth a high temperature; and if, as some suppose, at one period of its history, the air had mixed with it a larger proportion than at present, an increased temperature from its own action, as well as from increased weight, must have necessarily resulted."[11][12]

Foote's paper, Circumstances affecting the Heat of the Sun's Rays, was accepted at the eighth annual AAAS meeting on August 23, 1856 in Albany, New York. For reasons that are unclear Foote did not read her paper to those present—women were in principle allowed to speak publicly at the conference—and her paper was instead presented by John Henry of the Smithsonian Institution. Henry introduced Foote's paper by stating "Science was of no country and of no sex. The sphere of woman embraces not only the beautiful and the useful, but the true".[13]

Foote's paper was published in 1856 under her name in the American Journal of Science and Arts,[12] immediately following a paper by her husband, Elisha. It was not however included by the AAAS in their annual publication of the association's meetings.[12] Summaries of Foote's work were included in the 1857 edition of the Anneal of Scientific Discovery, the New York Daily Tribune, the Canadian Journal of Industry, Science and Art,[14] Scientific American (1856), Jahresbericht (1856) and the Edinburgh New Philosophical Journal (1857).[15] Both European summaries omitted her direct conclusions about the impact of carbon dioxide on climate, and the summary written in the Edinburgh New Philosophical Journal named Foote's husband Elisha as the author.[15] Foote was praised in the September 1856 issue of Scientific American titled "Scientific Ladies." Impressed with how her findings were backed up by her experiments, The authors stated, "this we are happy to say has been done by a lady.”[12]

Foote's work had shown that the heating effect of sunlight was affected by CO₂ and water vapour in the atmosphere. This may have been the first scientific research to demonstrate the existence of what are now known as greenhouse gases.[16] Three years later, John Tyndall reported his more sophisticated research which showed that various gases both trapped and emitted infrared thermal radiation rather than sunlight. His work was published by the Proceedings of the Royal Society, where he was a fellow, and is commonly regarded as foundational to climate science. He gave credit to Pouillet's work on solar radiation through the atmosphere, but appears to have been unaware of Foote's work, or did not think it was relevant.[1][17] Foote's work is discussed by Ralph Lorenz in a modern planetary climate context, who notes that the near-infrared (0.8 to 3 μm) radiation absorption reported by Foote is effectively an "antigreenhouse effect" because it involves primarily solar radiation absorption rather than absorption and re-radiation of terrestrial longwave ('thermal') infrared radiation. This distinction was not fully appreciated in the 1850s.[18]

In addition, in 1867 Foote developed a new paper-making machine that produced paper described as being 'a marked improvement on the ordinary sorts in respect to strength, smoothness and facility for tearing evenly'.

Foote worked on electrical excitation of gases and in August 1857 published an article in the Proceedings of the American Association for the Advancement of Science, which discussed her attempt to find a connection between fluctuations in atmospheric pressure and variations in its electric charge. During the 19th century, 16 physics papers were published by American women; of which two—both written by Foote—were published before 1889.[15]

Eunice Foote and her husband Elisha were both inventors. Foote received a patent in 1860 for a "filling for soles of boots and shoes" made of "one piece, of vulcanised india-rubber" to "prevent the squeaking of boots and shoes".[6][19]

In 2010, retired petroleum geologist Ray Sorenson came across Foote's work in a 1857 volume of The Annual of Scientific Discovery. He found that Foote had been the first to propose a connection between carbon dioxide and climate change and that her work had gone unrecognized,[13] In January 2011, Sorenson published his findings on Foote.

A movie about Foote's life, Eunice, was produced in 2018.[20] In May 2018, a symposium on Foote's work, Science Knows No Gender: In Search of Eunice Foote Who 162 Years Ago Discovered the Principal Cause of Global Warming was held at the University of California, Santa Barbara.[22] In November 2019 the university library displayed an exhibit to honor Foote's work and legacy, presenting the claim that she had discovered that "CO₂ is uniquely proficient at absorbing and radiating solar heat back to earth". John Perlin, a physicist at the university, has described Foote "the Rosa Parks of science".[23]

An analysis of Foote's 1856 paper was published in 2020 by Joseph D. Ortiz, and Roland Jackson. In addition to a description of how Foote related changes in the types and amounts of atmospheric gases, including carbon dioxide, to warming and changes in climate, their analysis traces the derivation of her ideas and explores how she constructed, carried out, and interpreted her experiments.[24]

Jackson, a visiting scholar at the London-based Royal Institution, set out to analyze the social context and questions of priority of Foote's work. Foote's paper gives only outline information about her apparatus and does not name those who influenced her. Similar apparatus had been introduced in the 1770s by de Saussure, and Foote deserves credit as the first to experiment with different gases. Scientists in Europe were looking into the roles of sunlight and "obscure heat" or "terrestrial radiation" (now known as infrared) in what we now call the greenhouse effect, and Tyndall cited de Saussure, Fourier, Pouillet, and Hopkins as inspiring his research into its molecular physics. He used infrared sources, and developed Melloni's apparatus to get accurate measurements: Foote's simple apparatus could not distinguish between visible and infrared radiation. Not all researchers were aware of each other: it took two years after publication before Tyndall and Gustav Magnus realized they were both working on this topic. Foote was an amateur at a time when women were excluded from many scientific societies, and few European publications mentioned her work. Joseph Henry (who had read out her paper) could have promoted it, but did not grasp its significance, so her speculation that CO₂ variation could have changed climate gained little attention. Transatlantic travel was infrequent, and though America was advanced in natural history, physics was still developing and few American physicists had an international reputation.[15]

• Foote, Eunice (September 1856). "Circumstances affecting the Heat of the Sun's Rays". The American Journal of Science and Arts. 22 (65): 382–383.
• Foote, Eunice (1858). "On a New Source of Electrical Excitation". Proceedings of the American Association for the Advancement of Science: Eleventh Meeting. Cambridge, Massachusetts: Joseph Lovering: 123.