Sweden’s domestic shipping emits almost twice the amount of air pollution and greenhouse gases than previously thought and, therefore, domestic shipping has a greater environmental impact than domestic flights.

The Swedish Meteorological and Hydrological Institute now collects emission data by tracking all vessels that go between Swedish ports with the help of GPS data. The new data suggests that domestic shipping uses twice the amount of fuel than previously thought, generating twice as many emissions.

The new emissions survey method suggests that Sweden’s domestic shipping was responsible for 662,000 tonnes of carbon dioxide equivalent in 2016, while domestic air traffic emits 554,000 tonnes.