In January 2022, the Hunga Tonga volcano erupted with such violence that it became, without anyone's intention, one of the largest atmospheric chemistry experiments in recorded history. Months later, scientists studying satellite data discovered that the eruption's plume was destroying methane at a rate of roughly 900 metric tons per day — a scale never before observed in nature. The mechanism appears to involve reactive chlorine born from the unlikely marriage of volcanic ash, seawater, and sunlight high in the stratosphere, offering a rare window into how Earth's atmosphere processes one of