Giant ships lurked off the California coast for weeks in April and May, their bellies full of up to 20 million barrels of oil. This floating cache, enough to support the energy needs of the entire U.S. for a day, sat aboard an idling fleet that pumped out tons of pollutants, according to a new analysis performed by the University of College London and shared with National Geographic. These emissions could ultimately affect the long-term health of coastal communities—many of them already at risk and underserved—and they added tons of climate-warming carbon dioxide to the atmosphere.

Despite U.S. energy demand plummeting to record lows due to the coronavirus crisis, oil kept getting pumped out of the ground. The resulting oversupply