A colossal underwater volcano in the South Pacific may have revealed a surprising new weapon against climate change. After the 2022 eruption of Hunga Tonga–Hunga Ha’apai, scientists detected enormous amounts of formaldehyde in the atmosphere — a telltale sign that methane, one of the planet’s most powerful greenhouse gases, was being destroyed. Researchers now believe volcanic ash mixed with salty seawater and sunlight created reactive chlorine particles that effectively ‘cleaned up’ some of the methane released by the eruption itself.