On a damp, foggy January morning in 1793, Louis XVI, besieged monarch of France, stood before a guillotine.
To some 20,000 of his angry subjects, Louis declared: “I die innocent of all the pretended crimes laid to my charge. I forgive all those who have had any hand in my misfortunes, and I pray that my blood may be of use in restoring happiness to France—and you, unhappy people!”1 The rest of his speech was cut short. The king was strapped to a plank, slid through the “widow’s window,” and decapitated.
What Louis could not have known was that one root of his “misfortunes” was not any one of his subjects. It was El Niño, the climatic fluctuation that has sown misfortune for humankind for millennia.
Today, as global temperatures rise, El Niño events will likely become more dramatic—causing longer, drier droughts, extreme floods, and more unpredictable weather. Stories of how El Niño shaped history are thus more than mere curiosities, says Brian Fagan, author of Floods, Famines, and Emperors: El Niño and the Fate of Civilizations.
“You cannot study climate change without looking at human experience of climate in the past,” he says. We might live in a world of billions more people, but past El Niños can still offer insights into human behavior. “They won’t tell you how to do something,” Fagan says, “but they can give you precedents for how you might.”
El Niño is one stage of a much larger cycle in Pacific Ocean weather patterns—a cycle known as the El Niño-Sothern Oscillation, or ENSO. “El Niño” happens when westerly trade winds cross the Pacific and weaken; air pressures plummet in the eastern Pacific as a result, and warm water builds up around the Americas.
The force and direction of the Pacific winds have worldwide impacts, in ways that are still not completely understood. “Each El Niño episode,” according to NASA’s website, “has a unique timing and variations in impacts.”
Take, for example, Europe: It’s believed that as the South Pacific Ocean warms, air pressure drops in the North Pacific, causing anomalies downstream over North America and northwestern Europe. These changes can speed up the polar jet stream, the fast-moving air current that circles Earth’s upper latitudes like a belt, and increase activity in swirls of air over the Atlantic called eddies. All of this can add up to very strange weather—like that which France saw in the late 1700s.
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