The carbon footprint of global tourism accounts for 8% of emissions, almost four times larger than previously thought, suggests a paper published online this week in Nature Climate Change. The findings indicate that efforts to decarbonise the industry are being outpaced by increased demand for energy-intensive travel.

Global tourism is a trillion-dollar industry with large-scale environmental impacts. Previous research quantifying the carbon footprint of the industry suggests that emissions from tourism account for 2.5-3% of global greenhouse gas emissions. These estimates, however, often do not account for emissions embodied in transportation choices as well as those from food and beverage, infrastructure, and retail services at destinations.

Arunima Malik, Manfred Lenzen, and colleagues conduct a comprehensive analysis of global tourism using two different accounting procedures, which allocate emissions from a tourist’s country of residence to their destination and back again. This allows the authors to calculate emissions estimates across the lifecycle of international travel. Their findings indicate that tourism accounts for about 8% of global greenhouse gas emissions, and that the carbon footprint of international tourism increased between 2009 and 2013. They also find that travel between high-income countries is a large contributor to tourism’s carbon footprint, and that the increase in emissions is driven by growing affluence.

The authors conclude that efforts to encourage less carbon-intensive travel have so far been unable to limit the growing carbon footprint of global tourism.