One way to read Fourier’s story is as a poor, orphan boy who just wants to sit and do loads of really hard maths, but French politics just keeps getting in the way. Or he was an increasing ill man who puzzles over why he can never quite stay warm enough. Either way, he’s generally credited as dreaming up the idea of the greenhouse effect, which is why he gets an entry here. If I was doing this history chronologically I might start with Fourier.
The son of a tailor, Jean Baptiste Joseph Fourier was born in March 1768, in Auxerre, a little over 100 miles southeast of Paris.
By the time he was nine, he'd lost both his parents and – perhaps luckily for him – was placed in the local military school. There, he reportedly discovered his love of maths. There’s a story of a monk discovering him one night, huddled up in a classroom using the light of a load of discarded candle ends to solve equations. Stories like that of famous scientists’ childhoods should be taken with a bucket-load of salt, but it’s a sweet image nonetheless.
Jobs in the scientific corps of the army were reserved for men of more noble birth than tailor’s sons, but Fourier hoped to join a seminary in Paris, and find space for maths there.
But the French Revolution got in the way.
Fourier was highly sympathetic to the cause and joined his local revolutionary committee, raising money for the war with Europe and acting as a sort of local spy. As the 1790s crept on, however, he started to regret it. His intellectual heroes Nicolas de Condorcet and Antoine Lavoisier had both been killed. More locally, he stood up for families targeted by the Terror.
A pause for some European history in case, like me, you were ill the day you did that bit of the French Revolution in history class. The Terror was a period between autumn 1793 and summer 1794 when, following intense conflict between two rival political factions, the revolutionary government decided terror was the way to go, and issued mass arrest and executions of people dubbed enemies of the revolution. It’s hard to know exactly how many people died, but it’s in the region of tens of thousands, with hundreds of thousands of arrests.
In July 1794, Fourier was arrested and imprisoned, facing the guillotine. Or rather, I say July because that’s what we’d call it now, but in Revolutionary France it was Thermidor (heat), the eleventh month of the French revolutionary calendar. It is kind of poetic when you know some of the rest of Fourier’s story (not to mention the rather politically hot position he found himself in at the time).
Fourier somehow wrangled an audience with Robespierre himself, to plead for his life. Apparently it was a very eloquent, persuasive speech. But still Robespierre dismissed him. Fourier was sent back to jail, and he must have expected to die soon after. But the guillotine got to Robespierre first. And Fourier was released.
He enrolled as a student at the newly established École Normale. This had been established in part to rebuild trust between the republic and the country's elites after the Terror. But, Paris still being a complicated place at the time, it closed within a year. In 1795, Fourier joined the newly established école Polytechnique in 1795, this time bagging a job as an assistant lecturer, supporting teaching of mathematicians Joseph-Louis Lagrange and Gaspard Monge. But the new regime were suspicions, and poor Fourier was arrested again, this time for supporting Robespierre. Fourier colleagues protested the arrest and he was released.
Sadly, however, dreams of just sitting down with a big pile of very hard sums were once again smashed when, in 1798, Monge selected Fourier to join Napoleon’s Egyptian campaign as scientific adviser. There he was appointed secretary of the Institut d'Égypte. He also helped organise munitions for the French army, did some diplomatic work, and did a bit of light maths on the side.
He started his work on heat in Egypt. There is no evidence to suggest this was because it was so much hotter than Paris, though he was interested in the unequal heating of the globe (I mean, why is it hotter in Cairo than Paris?) and by 1816, had written a 650 page manuscript on the subject.
We also know that he got ill Egypt and never fully recovered. It’s not clear what was wrong with him, but historians think he ended up with severe hypothyroidism – he certainly developed a very poor ability to tolerate cold. In France, he always wore a thick overcoat, even in the summer, and reportedly kept a second with a servant in case he needed further insulation. He kept his apartment as warm as possible, and hated being out in the cold.
So perhaps his health was one of the reasons he developed such a fascination for heat. But then again, a lot of early 19th century scientists were into the topic – it could have just been fashion and interest, and a sense that he could make a name for himself with the topic.
Fourier returned to Paris in 1801, hoping to go back to his work at the Polytechnique. But Napoleon had other plans – he appointed him prefect of Isère, an area in the east of France which at the time stretched to the Italian border. His work there mainly seemed to work on draining marshland and building the road between Turin and Lyons. But he managed to get on with some more maths on the side.
Fourier was still working in Grenoble in 1814 when Napoleon fell, and managed to take the opportunity to come to Paris to take up research full time. In 1816 he was elected to the reconstituted Académie des Sciences, but Louis XVIII could not forgive his work with Napoleon, so the nomination was refused. After some negotiation, he was allowed in the following year and in 1822 even elected to the powerful position of secrétaire perpetual.
In 1822, he published an Analytical Theory of Heat, his key work. But we don’t really care about that. What we care about is his 1827 follow-up paper on the temperature of the Earth and interplanetary space. Today, it’s generally seen as the origin of the idea of the greenhouse effect.
Here’s the science bit. In case you were sick the day you studied that too, or just got distracted by all the pictures of people gardening. The greenhouse effect is the way us humans have decided to describe the natural process by which the atmosphere traps some of the Sun's energy. It's a good thing. Without it, we'd be really cold. But if we increase this effect too much (which, we've worked out, we're doing with so-called 'greenhouse gases' like carbon dioxide) it could get too warm, which the pickle we find ourselves in now. A greenhouse isn’t exactly the best metaphor for it, and bits of history of climate science get their knickers in a twist about that, but it works pretty well as a loose explanation. If you’re still puzzled, just think of it as the way we understand how the atmosphere keeps us warm and is getting warmer. And/ or have a look at the Nasa kids explanation on it – it’s really clear and has a picture of a snowman and some tomatoes.
Back to Fourier. He’d been thinking about the size of the Earth,and its distance from the Sun, and calculated that considering both these things, it probably should be a lot colder than it was. I mean it was cold, granted, he was wearing two coats and had a roaring fire on. But surely it should be much, much colder still?
As historian James Rodger Fleming argues, Fourier didn’t give us the phrase the greenhouse effect. He thought of the atmosphere more like something called an heliothermometer. This was designed in the 1760s by a Swiss scientist called Horace-Bénédict de Saussure. It was a small wooden box lined with a layer of black cork with three panes of glass stuck in it. Sunshine would enter the box through a window and, due to the glass and black cork, it’d get really hot in there. Saussure would take it up mountains and used it work out that solar heat increased with altitude. Or, more simply, it got really hot in those boxes (Saussure’s sometimes credited with the invention of the solar oven.) and Fourier wondered if the atmosphere worked a bit like that. He sort of imagined the atmosphere as being a massive version of one of those boxes, sandwiched between the Earth and interstellar space.
If you want to read Fourier’s paper yourself, William Connolley offers a translation. It includes a line about how the action of human societies are able to make to vary the climate, but we should be careful of reading early 19th century science through 21st century spectacles. Like Arrhenius and others who followed him, he was probably more worried the climate would get cooler, and wouldn't have expected humans to have had the sorts of impacts they have. In tracing the history of the greenhouse effect, we should also remember the role of Claude Pouillet who developed Fourier's work, and people like de Saussure who we drew on. It's neat to say Fourier discovered the greenhouse effect, but science just isn't that neat.
Fourier died not long after this paper, in May 1830, having suffered a large heart attack. There a few memorials to him. However, fittingly perhaps, the forces of heat, climate and politics have eroded them somewhat. A bronze statue to him in Auxerre was melted down for armaments by the Nazis during WW2 and the statue on his grave at Père Lachaise Cemetery is heavily weathered, with a spookily missing nose. His name is one of the 72 names inscribed on the Eiffel Tower though, if you want to give him a wave next time you’re there (though check out its wind turbines too.)
Next time: one of the best beards in the history of climate science (maybe the whole of the history of science).