Irish physicist John Tyndall is commonly credited with discovering the greenhouse effect, which underpins the science of climate change.
Starting in 1859, he published a series of studies on the way greenhouse gases including carbon dioxide trapped heat in the Earth’s atmosphere.
A recently digitised copy of The American Journal of Science and Arts suggests a woman beat him to it, however.
It includes a presentation by Eunice Foote to a top US science conference in 1856. She describes filling glass jars with water vapour, carbon dioxide and air, and comparing how much they heated up in the sun.
“The highest effect of the sun’s rays I have found to be in carbonic acid gas,” she writes, using the contemporary term for carbon dioxide.
“The receiver containing the gas became itself much heated – very sensibly more so than the other – and on being removed, it was many times as long in cooling.”
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She goes on to speculate that concentrations of carbon dioxide in the air could influence global temperatures.
“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.”
Wow @KHayhoe! Didn’t know that Eunice Foote identified CO2 as a greenhouse gas in 1856, a few years before Tyndall: https://t.co/QNaY89866c
— Ed Hawkins (@ed_hawkins) September 1, 2016
Climate scientist and communicator Katharine Hayhoe found Foote’s contribution after a colleague asked why there were no women in the history of the discipline.
Her interest piqued, Hayhoe has approached local historians and Foote’s descendents through a family history website to try and find a picture of her or more information.
Foote’s results were not definitive, Hayhoe says, with too many uncontrolled factors in the experiment. She could not have anticipated that atmospheric CO2 levels would rise from 290 parts per million at the time to 400ppm, prompting a global crisis.
Still, her hypothesis was prescient and a version of her experiment is used to teach high school children today.
“There was a bit of luck involved,” says Hayhoe, “but I think it is amazing that she connected the dots and came to a conclusion that subsequent science has proved to be correct.”
Hayhoe is not the first to resurrect Foote’s legacy. In 2011, independent researcher Raymond Sorensen got an article published in the journal AAPG Search and Discovery.
He relied on an observer’s account of Foote’s presentation, not having access to her own words. The report, by a David Wells in the Annual of Scientific Discovery for 1856, hints at how unusual it was for a woman to appear at such a gathering.
It states: “Prof. Henry then read a paper by Mrs. Eunice Foote, prefacing it with a few words, to the effect that science was of no country and of no sex. The sphere of woman embraces not only the beautiful and the useful, but the true.”
Eunice Foote, born Newton, would have been unlikely to get the opportunity without the support of her husband, Elisha Foote. Judging by the related paper Elisha presented at the same conference, it seems the married couple worked together.
They feature in The Road to Seneca Falls, an account of the women’s rights movement of the time. Elisha was a judge specialising in patent law and patented several inventions himself, according to author Judith Wellman, including a skate, drying machine and a reaping and binding machine. Eunice patented a “filling for soles of boots and shoes” in 1860.
Tyndall does not appear to have heard of Foote’s work when he started on a similar line of inquiry. His publications are more extensive and include accurate quantification of how much different gases absorbed infrared radiation – “radiant heat” – from the sun.
“With the exception of the celebrated memoir of M. Pouillet on Solar Radiation through the atmosphere, nothing, so far as I am aware, has been published on the transmission of radiant heat through gaseous bodies,” he wrote when presenting his initial results to the Royal Society of London in 1859, as cited by Sorensen.
“With regard to the action of other gases upon heat, we are not, so far as I am aware, possessed of a single experiment.”
It can be hard to assess claims of priority in science, says Sorensen, particularly if work is not in the public domain.
But he adds: “It is clear that Eunice Foote deserves credit for being an innovator on the topic of CO2 and its potential impact on global climate warming.”