On June 15, 1991, the sky over Central Luzon turned white as Mount Pinatubo sent an ash column 40 kilometres into the stratosphere. The central question this episode tackles is whether the canonical 0.5 degrees Celsius of global cooling attributed to Pinatubo is actually reliable — and what is at stake if it is not. Ola and Amara trace the mechanism of stratospheric aerosol forcing from Pinatubo's 22-day global circumnavigation to the contested Toba supervolcano eruption of approximately 74,000 years ago, then scale further back to the Siberian Traps and Deccan Traps of the Permian and Cretaceous periods, roughly 252 and 66 million years ago respectively. They close on the termination shock problem in geoengineering research. Listeners interested in climate science, deep-time geology, or the governance of solar radiation management will come away with a clearer sense of how much certainty — and how much uncertainty — rests on a single volcanic event.