Container ships supply people all over the world with goods, while cruises attract millions of passengers every year. But ships also cause around three percent of global greenhouse gas emissions. This is despite the fact that emission-free maritime trade has been possible for thousands of years - thanks to the wind. "We need to get back to sailing ships," says Captain Andreas Lackner. Fifteen years ago, the Austrian and two friends put a sailing cargo ship into operation. The "Tres Hombres" has been working since 2010, transporting up to 40 tons of goods across the seas without an engine. The clipper ship takes cocoa and rum from the Caribbean to Europe, or 20,000 bottles of organic wine from La Rochelle to Copenhagen. "We’re closing the gap between fairly paid producers of organic goods and conscious consumers," says Lackner. Others have also rediscovered the power of the wind. Ralf Oltmanns from East Frisia sailed the world's oceans at the age of 16, before founding an advertising agency. Now, 30 years later, the passionate sailor has developed a new twist on a century-old propulsion system in order to make large ships cleaner. The Flettner rotor, named after its inventor, Anton Flettner, is a type of sailing machine: a cylindrical structure that rotates in the wind to generate thrust. Oltmanns has used the original invention to create a modern product. "Depending on the size of the rotor and the wind conditions, a freighter can save between 5 and 25 percent on fuel," the 63-year-old calculates. The rotor could make both cargo and passenger ships more climate-friendly. Anna Braren was convinced by his idea: Her shipping company equipped its first ship with the Flettner rotor in 2021. With countless innovations and strict regulations, Norway is leading the way in the transition to emission-free shipping. The Scandinavians are focusing on electric motors and hybrid technologies. Climate change is already being felt in the Norwegian Arctic - another reason why the government is getting serious. From 2026, only emission-free ships will be allowed to sail in Norway's most beautiful fjords. And climate-friendly tourist ships are already sailing along the traditional postal ship route.