How long have we known about climate change? The answer might surprise you.

Global warming, climate change, the greenhouse effect, and carbon emissions only became mainstream terms relatively recently. So you’d be forgiven for thinking that the science behind climate change has only been understood for a short period.

Believe it or not though, the first scientific discoveries relating to the burning of fossil fuels and consequent impacts on the climate took place way back in the early nineteenth century. So who were these climate science pioneers? Let’s meet them.

Joseph Fourier was a French mathematician who was most famous for his work on heat conduction, for which a mathematic series now bears his name. However, it is another piece of work that earns him a place in the scientific history of climate change. In 1824 Fourier calculated that an object the size of Earth, given its distance from the Sun, should be considerably colder than it is if warmed only by solar radiation. Fourier’s consideration that the atmosphere may insulate the planet and therefore allow for warmer temperatures is the first proposal of the greenhouse effect (although Fourier never used that term).

It was another Frenchman, Claude Pouillet, who in 1838 speculated that water vapour and carbon dioxide were responsible for causing these warmer temperatures. Neither Fourier nor Pouillet produced any experimental evidence to support their theories though.

Those experiments were conducted independently by Eunice Foote and John Tyndall. Born Eunice Newton, Foote was a relatively obscure scientist from the eastern United States, while Tyndall was a Fellow of the Royal Society. In 1859 Tyndall set up an apparatus at the Royal Institution in London to conduct experiments on the absorption of heat by gases. He soon established that carbon dioxide and water vapour both absorbed and radiated heat, the physical basis of the greenhouse effect. “What Tyndall had demonstrated unambiguously, and indeed for the first time, was the absorption and radiation by certain gases of what we now call long-wave infrared radiation”. In a lecture published in 1861, Tyndall set out his findings and acknowledged the prior work of Fourier and Pouillet.

Whether accidentally or deliberately he did not reference the work of Foote, who it turns out made a similar discovery three years earlier, in 1856. Her experiments were crude when compared to Tyndall’s and she did not specifically refer to long-wave infrared radiation, but “it now appears that Foote was the first to demonstrate the greenhouse effects of certain gases and also the first to theorize about their interaction with the Earth’s atmosphere over an extended period of time.”

With the existence of the greenhouse effect now known, Swedish professor Svante Arrhenuis began to theorise on how an increase or decrease in the amount of carbon dioxide in the atmosphere would affect the Earth’s temperature. He calculated (by hand in a tedious process that took months) that a significant decrease in carbon dioxide could trigger an ice age and that a doubling of carbon dioxide in the atmosphere could lead to a 11 to 14.5 degree Fahrenheit rise in temperature. His work was published in 1896 and also cited that of Arvid Högbom, which provides the first estimate of the amount of carbon dioxide emitted into the atmosphere from the burning of fossil fuels (incidentally the chemical reaction that produces carbon dioxide from the combustion of charcoal was first hypothesised by Flemish chemist Jan Baptist van Helmont in around 1640 and is now accepted as scientific fact). A compatriot of Arrhenuis and Högbom, Nils Gustaf Ekholm, perhaps because his homeland was of a colder climate, painted a rather optimistic picture of this phenomenon, stating “thus it seems possible that Man will be able efficaciously to regulate the future climate of the earth and consequently prevent the arrival of a new Ice Age.”

A deadly heatwave soon after prompted an article by Francis Molena in Popular Mechanics entitled 'Remarkable Weather of 1911: The Effect of the Combustion of Coal on the Climate — What Scientists Predict for the Future' to state:

“The furnaces of the word are now burning about 2,000,000,000 tons of coal a year. When this is burned, uniting with oxygen, it adds about 7,000,000,000 tons of carbon dioxide to the atmosphere yearly. This tends to make the air a more effective blanket for the earth and to raise its temperature. The effect may be considerable in a few centuries.”

While several scientists had now established the link between carbon dioxide in the atmosphere and temperature, no one had yet quantified the effect. That task fell to Guy Callendar, a steam engineer by trade, but whose amateur forays into meteorology are what he is best known for. In 1938 he published a paper entitled ‘The Artificial Production of Carbon Dioxide and Its Influence on Temperature’. Callendar compiled historic temperature records from the nineteenth century on and compared them to measurements of atmospheric carbon dioxide levels, finding that in the 50 years prior fuel combustion had added 150,000 million tons of carbon dioxide to the atmosphere and in the same period world temperatures had risen by an average rate of 0.005 degrees Celsius each year. He calculated (albeit on flimsy evidence) that a doubling of carbon dioxide in the atmosphere could eventually lead to a two degree rise.

Many meteorologists gave Callendar’s claims little credence, arguing that historical carbon dioxide measurements he relied on were untrustworthy and didn’t allow for natural variation in carbon dioxide levels. It wasn’t long until a more accurate method was developed though. American scientist Charles Keeling had built instruments that made much more accurate measurements of carbon dioxide levels as a young researcher at the California Institute of Technology and in 1958 began gathering data from those instruments at Mauna Loa in Hawaii. The first reading Keeling took was 315 parts per million, a number that had risen to 380 by the time of his death in 2005. The chart that plots the rise in carbon dioxide levels is known as the Keeling Curve, and owing to Keeling’s fastidiousness stands unchallenged as unequivocal evidence of the rising carbon dioxide levels in Earth’s atmosphere.

The Keeling Curve is a daily record of global atmospheric carbon dioxide concentration maintained by Scripps Institution of Oceanography at UC San Diego

So there you have it – since the early nineteenth century scientists have been working to identify and understand the greenhouse effect, in the process realising that carbon dioxide levels are rising and drawing links to the burning of fossil fuels. So how did world leaders and big business respond when presented with these findings? More on that another time!