How Did Humans Discover Climate Change?

The year was 1938, a British engineer's holiday was about to change the world. His name was Guy Calendar. That year, he decided to take a break, but instead of relaxing, Calendar had other ideas. He pursued his true two great loves: bikes and meteorology. Calendar started collecting records from various weather stations, around 147 in total. Remember, this was before the computer, so all the calculations were done by hand.

And what did he find? Global temperatures had been rising by around 0.3°C in 50 years. It was a landmark discovery. The only question left was why. Calendar blamed it on carbon dioxide. He said emissions from the industry were responsible. In hindsight, even emissions from his own beloved bikes. None of it mattered, though, because in 1938, no one took him seriously. For starters, he was an engineer, not a scientist. So people said it's not his field of expertise. Also, the idea itself was too big to accept – that human beings could alter the temperature of something so big, our planet. So Calendar's work was dismissed.

Interestingly, he did not think that global warming was bad. He thought it was good. So how did we go from denying global warming to accepting it? How did we link it to greenhouse gases? Also, how did the whole Greenhouse analogy come about? Time for a flashback.

Where do you think the climate change timeline begins? The 19th century? Maybe the 20th century? Well, both answers are wrong. Even the ancient Greeks had an inkling about it, like this man Theopus. He was a disciple of Aristotle. Now, he did not have computers or fancy machines, so he simply observed. And what did he see? In the Tess region, temperatures cooled when the marshes were drained in Philippi. When the forests were cut, it became warm. So Theopus joined the dots: human actions led to climate change. He couldn't quantify or prove it, but he knew what was happening.

Such localized climate change theories have been around for a long, long time. Some of them turned out to be fake, like "rain follows the plow." It was all the rage in the 19th century. People thought human settlement would lead to more rainfall. For example, assume there's a piece of arid land. It's all dry with no rain. Suddenly, people decide to settle there. They begin plowing the land to cultivate crops. In the 19th century, people thought this would lead to rainfall. Just stay in some place, plow the land, grow some crops, and rain would follow. Of course, it doesn't work like that. Such ideas were limited to certain regions. It was all localized. None of them thought global climate change was possible, that too by human action. But without knowing it, we were setting the stage for it. I'm talking about the Industrial Age.

We built the steam engine; we built dozens of factories. All of it was done by burning coal. This became Ground Zero for climate change, for global warming. And when did we realize this? Well, it took a lot of time. In the 1820s, we took one major step forward. We understood the Greenhouse Effect. And it was proposed by this man, Joseph Fier, a French physicist. And his logic was quite simple: sunlight brings heat to the Earth. If the Earth reflected all of it back, it would be a cold wasteland. But the Earth is not a cold wasteland, meaning some of the heat is stored within it, is trapped. Now, Fier said the atmosphere is doing all of this, it is trapping some of the heat from the sun, which is exactly what a greenhouse does.

Other scientists built on this theory. One of them was Eunice Newton Foot. She was an amateur scientist in the United States in the 1850s. She conducted crucial experiments. Again, the concept was simple. She put mercury thermometers inside different glass cylinders. And what did she observe? The cylinders with carbon dioxide were hotter. So Foot joined the dots: there was something about this gas, this carbon dioxide. It had the ability to make the air hotter. In 1856, her work was presented at the AAAS, the American Association for the Advancement of Science. But guess who presented it? Not Foot, but her male colleague. Welcome to the 19th century. Foot's work was largely ignored during her lifetime. It was only recently that she's been acknowledged.

Three years after Foot's paper, another one was published, this time by John Tindle, an Irish physicist. Now, if you're in school right now, you may recognize this name, John Tindle, especially from the Tindle effect. But don't worry, we will not go into that. We are focusing on his climate change experiments. Tindle refined what Unis Foot found; he proved the greenhouse effect, that gases like carbon dioxide could absorb heat. That's what he proved. His paper credits another scientist named Mapu, but it doesn't mention Foot. Maybe he did not know about her work, or maybe he thought it was not relevant. Either way, by the late 1800s, scientists knew a couple of things: the greenhouse effect was real, and gases like carbon dioxide could trap more heat.

Just one problem, though: no one looked at the larger picture. No one applied these findings to our planet's temperature. It finally happened in the year 1895, thanks to a Swedish chemist, Swant Arenus. He wasn't actually studying global warming; he was studying the opposite. He was looking at global cooling. Arenus was trying to explain the Ice Ages, what would have caused it. He zeroed in on carbon dioxide. First, he gathered data on global temperatures, then he began calculations. And guess how many? Between 10,000 and 100,000. That's how many calculations it took Arenus. One year later, in 1896, he published his paper, and the takeaway was simple: if CO2 levels were halved, temperatures would fall by 4 to 5°C. So, lesser the CO2, lesser the temperature. It was job done for Arenus. But soon, he started wondering, what if the opposite happened? What if CO2 levels doubled instead of halved? Then, temperatures would rise by 5 to 6°C.

Not many people bought it, especially after hearing his next claim. Arenus linked CO2 levels to the burning of coal. He said CO2 levels would increase by 50% in 3,000 years. I guess he was wrong, not about coal, but about the speed because, in the 20th century alone, CO2 levels increased by 30%. Anyway, Arenus went on to win the Nobel Prize, not for climate change, though; that part of his work was always polarizing. His theory was finally proven in 1938. It was too late by then; Arenus died nine years before Guy Calendar's experiment.

So let's recap. Again, by the 1940s, scientists knew three things: the greenhouse effect was real, carbon dioxide was among the main culprits, and coal burning would lead to global warming. Just one problem: no one thought