Eunice Newton Foote

An 1856 column in Scientific American described Eunice Newton Foote's temperature experiments with gases and her findings that carbonic acid (carbon dioxide, CO₂) caused the greatest warming effect.

Foote conducted a series of experiments that demonstrated the interactions of the sun's rays on different gases. She used an air pump, four mercury thermometers, and two glass cylinders. First 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 CO
2, common air, and hydrogen.[10] Of the gases she tested, Foote concluded that carbon dioxide (CO
2) trapped the most heat, reaching a temperature of 125 °F (52 °C).[11] From this experiment, she stated "“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.”[12] 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."[13][14]

Foote illustrated her findings in a paper entitled, Circumstances affecting the heat of the sun's rays, which was accepted at the eighth annual American Association for the Advancement of Science meeting on August 23, 1856 in Albany, NY. It is not clear why Foote did not present her own work at the conference, as women were in principle allowed to speak, but the presentation of her paper was made instead by Prof. John Henry of the Smithsonian Institution. Before reading Foote's work, Henry introduced the findings 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".[15] Foote's paper was published later the same year under her name in the American Journal of Science and Arts.[14] However, this paper was not included in Proceedings from 1856, which was the published work from the AAAS meetings of the year.[16] A summary of Eunice Foote's work was published in The 1857 Anneal of Scientific Discovery, a book containing reviews of scientific progress in the year proceeding each publication (pg. 159–160).[17] Summaries of Eunice Foote’s findings were also reported in the New York Daily Tribune, Canadian Journal of Industry, Science and Art, and Scientific American as well as the European journals Jahresbericht in 1856 and the Edinburgh New Philosophical Journal in 1857.[18] However, Eunice’s brief recognition was not complete. 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 misrefers to the scientist as “Elisha Foote”, Eunice’s husband.[18] Meanwhile, Foote was praised in the September 1856 issue of Scientific American titled "Scientific Ladies." The authors were impressed with her findings backed up by her experiments, stating, "this we are happy to say has been done by a lady.”[16] An extensive analysis of Foote's 1856 paper was published in 2020 by Joseph D. Ortiz, a paleo-climatologist and Roland Jackson, a historian of science. Their work explores how Foote related changes in the types and amounts of atmospheric gases, including carbon dioxide, to warming and changes in climate. It traces the derivation of her ideas and explores how she constructed, carried out, and interpreted her experiments.[19]

Foote's work had shown that the heating effect of sunlight was affected by CO
2 and water vapour in the atmosphere. 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.[12][20] 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" (like nuclear winter or dust in the Martian atmosphere), and not the greenhouse effect which is due to absorption and re-radiation of invisible longwave ('thermal') infrared radiation. This distinction was not fully appreciated in the 1850s.[21]

Foote also worked on electrical excitation of gases and, in August 1857, her work was published again in the Proceedings of the American Association for the Advancement of Science.[5][22] She also 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".[8][23]

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'.[24]

Circumstances affecting the Heat of the Sun's Rays (1856 by Saratoga Springs, New York).[25][13]

Sixteen papers in physics were published by American women in the 19th century; only two of which were published before 1889 and both were written by Eunice Foote.[18]

A symposium about her work, Science Knows No Gender: In Search of Eunice Foote Who 162 Years Ago Discovered the Principal Cause of Global Warming was held May 2018 at University of California Santa Barbara, USA.[26]

In 2010, retired petroleum geologist Ray Sorenson came across Foote's work in a 1857 volume of Annual Scientific Discovery. He quickly realized that Foote was the first to make the connection between carbon dioxide and climate change and that her work had gone unrecognized.[15] In January 2011, Sorenson published his findings on Foote in AAPG Search and Discovery, where it received "more response than any of his other work". In November 2019 at University of California, Santa Barbara a lecture and library exhibit recognized Foote's contribution to climate science and her omission from the history of the field. “Foote’s story has never been more compelling because it enhances the visibility of women in science, and their significant contributions,”“I call her the Rosa Parks of science,” said John Perlin, a research scholar in the Department of Physics who is writing a book about Foote to make evident Foote's primacy in laying the foundation for understanding the greenhouse effect – a critical component of the climate system. He hopes to help restore her place among other early pioneers of climate science, such as John Tyndall and Svante Arrhenius.[27]

From a modern perspective it seems strange that Foote's work was not noticed by other researchers. Historian of science Roland Jackson, a Visiting Fellow at the Royal Institution, has set out to analyse the social context and questions of priority. 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 realised 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 CO
2 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.[28]

A short movie about her life entitled "Eunice" was produced in 2018.[29]