Making the wakes of ocean ships brighter could cool the Earth by 0.5°C and help combat global warming, according to a new modeling study. Other geoengineering studies have examined how greenhouse gas warming could be counteracted by making Earth’s atmosphere more reflective. But this is one of the first to look at using the bright, bubbly wakes of cargo ships as they crisscross the world’s oceans. Natural foaming agents in the sea—chemicals often derived from phytoplankton—help create bright, white microbubbles in ship wakes that persist for about 10 minutes. Now, climate scientists say that designer foaming agents could create even brighter wakes that last much longer. If these supercharged wakes were 10 times brighter and lasted 10 days instead of 10 minutes, they would cover 5.5% of the world’s oceans and cool the planet by 0.5°C by the year 2069, the researchers write in a 28 January publication of the Journal of Geophysical Research: Atmospheres. That’s enough to partially restore Arctic ice loss and offset the 2°C warming that could occur by then. Because most ship traffic is in the Northern Hemisphere, most of the cooling would be felt there, where it would be accompanied by a drop in precipitation. But the researchers acknowledge many uncertainties in the scheme. The foaming agent could interfere with ocean ecologies or inhibit the uptake of carbon dioxide by the ocean—effectively negating one of the major ways that the world’s oceans fight global warming naturally. But the idea is not completely crazy. The shipping industry is already experimenting with microbubbles, applied to the underside of ship hulls, to reduce friction and improve fuel efficiency. And global shipping traffic has increased fourfold since 1990—meaning that the ocean area available to reflect away heat is only expected to grow.