The paper refers to CO2 as "carbonic acid gas". At this time, did they know that CO2 was also produced by burning fossil fuels? Or by respirating living things?
I think other commenters have answered your question, but I thought I'd talk a little on carbonic acid.
Carbon dioxide partitions into water as carbonic acid. This is the key mechanism in ocean acidification. Of course the rate is affected by pH of the oceans, there's a buffering action going on between carbonate, bicarbonate, and carbonic acid depending on how many protons are available. It's also why pure water sitting open to the air will have a slightly acidic pH.
The oceans at the bottom have a decent layer of carbonate material accumulated from shells, which are also at equilibrium with the ocean, but the other direction (accepting protons). But since the oceans are so big, to increase the pH of the oceans you'd have to send the surface water to the bottom. Mixing the oceans is kind of a slow process -- around 500 years. But in theory we'll get some long term climate help from the ocean floor (well, if the methane clathrates don't get us first).
CO2 was first hypothesized specifically as a gas making up the difference in mass between charcoal and the remnants of burning it in the 1600's by Jan Baptist van Helmont[1].
That respiration of animals emits CO2 was determined at least by the 1750's.
A Google Scholar search based on "carbonic acid gas" and "coal" found Babington, William. "A case of exposure to the vapour of burning charcoal." Medico-chirurgical transactions 1 (1809): 83. at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2128797/pdf/med... :
> When carbon in combustion combines with oxygen we obtain carbonic acid gas, and at the same time in proportion to its moisture, more or less hydrocarbonous gas is evolved.
A Google Scholar search based on "carbonic acid gas" and "exhalation" found Allen, William, and William Hasledine Pepys. "XVII. On the changes produced in atmospheric air, and oxygen gas, respiration." Philosophical Transactions of the Royal Society of London 98 (1808): 249-281. at https://royalsocietypublishing.org/doi/pdf/10.1098/rstl.1808... with quotes like:
> In this experiment we meet with a remarkable fact, viz. that as much carbonic acid gas was given off in 5½ minutes, as in the former experiment in eleven minutes ; so that it appears, whenever atmospheric air is taken into the lungs, it returns charged with about 8 per cent, carbonic acid
Carbon dioxide partitions into water as carbonic acid. This is the key mechanism in ocean acidification. Of course the rate is affected by pH of the oceans, there's a buffering action going on between carbonate, bicarbonate, and carbonic acid depending on how many protons are available. It's also why pure water sitting open to the air will have a slightly acidic pH.
The oceans at the bottom have a decent layer of carbonate material accumulated from shells, which are also at equilibrium with the ocean, but the other direction (accepting protons). But since the oceans are so big, to increase the pH of the oceans you'd have to send the surface water to the bottom. Mixing the oceans is kind of a slow process -- around 500 years. But in theory we'll get some long term climate help from the ocean floor (well, if the methane clathrates don't get us first).