How One Volcano Froze an Entire Continent's Summer

In 1816, it snowed in June across New England and Europe. Crops died. People starved. And one volcano was responsible.

How does a single eruption halfway around the world freeze an entire continent's growing season? The answer is buried forty kilometers above your head.

When a supervolcano erupts, it doesn't just throw rock and ash. It blasts sulfur dioxide gas into the stratosphere — that's the calm, jet-stream-free layer 12 to 50 kilometers up. Down here in the troposphere, rain scrubs pollution out within days. But the stratosphere has no rain. So that sulfur dioxide reacts with water vapor and converts into tiny sulfuric acid droplets called stratospheric aerosols. Those droplets spread globally within months, forming a near-invisible veil that wraps the entire planet. That veil reflects incoming solar radiation back into space before it ever warms the ground. Tambora injected an estimated 60 megatons of sulfur dioxide. Global average temperatures dropped by up to 1.5 degrees Celsius. That doesn't sound like much — but for crops timed to precise frost-free windows, 1.5 degrees is the difference between harvest and famine.

Here's the part that makes it stranger: the sky didn't go dark. It turned vivid red and orange at sunset for years. Those same sulfur aerosols scatter shorter blue wavelengths and let longer red and orange wavelengths dominate at dawn and dusk. Scientists now believe Turner's famously fiery paintings from the 1810s and 1820s weren't artistic license — they were accurate historical records of Tambora's atmospheric fingerprint.

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