A new NASA climate simulation suggests that extremely large volcanic eruptions called “flood basalt eruptions” might significantly warm Earth’s climate and devastate the ozone layer that shields life from the Sun’s ultraviolet radiation. The result contradicts previous studies indicating these volcanoes cool the climate. It also suggests that while extensive flood-basalt eruptions on Mars and Venus may have helped warm their climates, they could have doomed the long-term habitability of these worlds by contributing to water loss. Unlike brief, explosive volcanic eruptions such as Pinatubo or January’s Hunga Tonga-Hunga Ha‘apai that occur over hours or days, flood basalts are regions...