When Mount Tambora erupted on the island of Sumbawa in modern-day Indonesia, it altered global weather patterns for years. The blast flung roughly 100 cubic kilometers of debris and huge quantities of sulfur dioxide high into the atmospheric stratosphere. There, the sulfur gas reacted with water vapor to form microscopic sulfate aerosol veils.
Carried by atmospheric circulation, this reflective aerosol transport blanketed the planet, reflecting solar radiation back into space. The result was 1816's infamous Year Without a Summer. Widespread frost and snow swept through North America and Europe during June, July, and August, destroying crops and causing severe famine.
The sudden temperature drop forced widespread social unrest, inspired Mary Shelley to write Frankenstein during a dreary summer indoors, and demonstrated how localized volcanic transport can alter global climate ecosystems overnight.