Step 1 : Introduction to the question "What caused the "Year Without a Summer" in 1816?"
Step 2 : Answer to the question "What caused the "Year Without a Summer" in 1816?"
Mount Tambora volcano erupted:
A gigantic volcanic eruption of Mount Tambora in Indonesia shot hot ash 20 miles into the sky. The pyroclastic cloud destroyed the city of Tambora and the ash spewing from the volcano spread across the Northern Hemisphere. This ash-cloud of sulfur-dioxide shot into the stratosphere, disrupting global weather patterns. The sunlight-absorbing cloud prevented the warming of the planet's surface, leading to decreased temperatures, constantly cloud-covered skies and above normal rainfall. Source: WashingtonPost.com