Sniffer drones to patrol world's busiest ports.

• Position: Brief article

Teams of drones are about to start policing the skies of some of the world's busiest shipping ports. Their target? Environmental rule-breakers. It might sound - and look - like something out of a Marvel Avengers movie, but for many ports around the world, these so-called sniffer drones are the best way to enforce new regulations aimed at cutting the air pollution caused by ships.

Regulators are bracing for rules that are meant to lower shipping's emissions of sulfur oxides, pollutants blamed for acid rain. Because the regulations, which start January 1, will require most of the world's ships to burn more...