Science & Technology

We've Known About Manmade Global Warming for More than a Century

Global warming is one of the political topics of the moment. It seems like every day climate scientists are announcing the next depressing statistic about where the planet is headed because of human activity. If only we had known earlier, we could have done something to stop this mess — right? We hate to break it to you, but scientists have been saying this would happen for more than a century.

Svante Arrhenius, OG Climate Scientist

It might surprise you to learn that scientists have been talking about the temperature of Earth's atmosphere for a very long time. For much of that time, however, the questions weren't over how human activity is affecting the atmosphere, but how it was possible that ice had covered the Earth just a few millennia ago. Using the work of scientists Joseph Fourier and John Tyndall before him, the Swedish scientist Svante Arrhenius sought to explain how it was possible for the climate to change that drastically in that short amount of time. The key to the answer, Arrhenius believed, was a molecule we're all too familiar with today: CO2, what the day's scientists called "carbonic acid" but what we refer to today as carbon dioxide. Tyndall had discovered that water vapor and CO2 could trap heat in the atmosphere, but Arrhenius honed in on the latter because while water vapor varies daily, CO2 levels change only slightly over time. If CO2 levels changed, perhaps from volcanic emissions, it would only slightly change the temperature of the atmosphere on its own. But that change would also alter the amount of water vapor, which would change global temperatures even more through the greenhouse effect.

Arrhenius's big discovery came in 1896 when his calculations predicted that if Earth's atmosphere had only half of today's CO2 levels, the temperature in Europe would be 4–5 degrees Celsius colder. That solved the mystery of how an ice age was possible. But the opposite was also true: If you added CO2 to the air, such as in the coal smoke coming from the factories of the day, you could raise the Earth's temperature. In fact, he estimated that human activity in 1896 was adding CO2 to the atmosphere about as fast as the geochemical processes that led us out of the ice age.

Why Didn't Anybody Do Anything?

Unfortunately, Arrhenius didn't consider this a big discovery. It was more of a side note — a "by the way, isn't this interesting?" For one thing, if humans burned coal at the same rate they did in 1896, Arrhenius estimated that it would probably take 3,000 years for the temperature to rise by the margin it had since the last ice age. Even if the CO2 levels rose faster than that, he and other scientists of the day figured that the oceans would absorb most of it. By 1908, it was clear that humans were burning coal at a faster rate than he had predicted, but even then Arrhenius thought the planet would take a few centuries to start warming.

Unfortunately, his predictions were off. The atmosphere really was warming, but it took scientists and policymakers nearly 100 years to finally recognize that fact and take steps to remedy the problem. In 1988, two international organizations formed the Intergovernmental Panel on Climate Change to assess the impact of climate change and come up with ways to fight it. Today, 97 percent of climate scientists agree that the planet is warming and that it's most likely because of human activity.

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For a Pulizer Prize–winning dive into our impact on the planet, check out "The Sixth Extinction: An Unnatural History" by Elizabeth Kolbert. The audiobook is free with an Audible trial. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer February 2, 2017

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