In the upcoming series of posts, I want to take us (you and me) back to the beginnings of climate science, to look at the early evidence for Global Climate Change and how that evidence has developed into our current state of knowledge. I want us to feel that we “own” this history and knowledge, as ownership aids advocacy. I intend to do this in a series of short vignettes. If you can devote a handful of minutes to each post, you and I will “own” the history of climate science together. In the tradition of this fact-based website, there will be links to the original research.

This will not be a comprehensive examination; other valuable histories of climate science are available (here, here, and here, for example). My website being a fact-rich zone, the “twist” I have chosen is to focus our history on the practical measurements. Prior to the history I will report and beginning in 1824, Joseph Fourier (French mathematician), Claude Pouillet (French physicist), John Tyndall (Irish physicist), Svante Arrhenius (Swedish physical chemist), and Thomas Chamberlin (American geologist) had proposed and developed a hypothesis that increases in atmospheric carbon dioxide, caused by the burning of fossil fuels, could cause the surface temperature of the Earth to rise due to what we now know as the Greenhouse Effect. You can read about that elsewhere. Their assertions were disputed by other scientists, at the time, based on a number of arguments. That water vapor was a much stronger absorber of solar radiation than carbon dioxide. That any excess carbon dioxide from fossil fuels would be rapidly absorbed by the vast oceans. Etc. The speculation was all well-informed (based on the available data at the time) but at an impasse

And here we begin.

In the years between 1898 and 1901, Dr. Horace Brown, a British chemist, and Mr. Fergusson Escombe, a British botanist, were at the Royal Botanical Gardens in Kew, England studying the influence of light and carbon dioxide levels on the rate of the photosynthesis reaction in leaves (Brown & Escombe, 1905). They constructed a rather ingenious apparatus:

Figure 1 of H. T. Brown & F. Escombe, On the physiological processes of green leaves; Proceedings of the Royal Society B 76 (1905), 29-111.

A leaf was housed inside a sealed box with a window. Air with a known carbon dioxide concentration could be pulled through the box while light of a measured intensity was made to shine on the window. The air from the leaf box was then pulled into the chemical apparatus on the right, within which the amount of carbon dioxide remaining in the air was measured by its reaction with sodium hydroxide to form sodium carbonate. This was a new method of measuring the concentration of carbon dioxide in air, at the time, and Brown & Escombe were pleased to find it was accurate enough to discern the small quantities of carbon dioxide consumed by a single leaf as it did photosynthesis. Naturally, Brown & Escombe had occasion in the course of this work to make a multitude of measurements of the carbon dioxide concentration in the ambient air at the Royal Botanical Gardens. It averaged about 290 ppm (parts per million).

So it was around 1900, and the atmospheric carbon dioxide concentration at the Royal Botanical Gardens was 290 ppm. To be continued…

Continue to 2nd episode

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