The multi-trillion dollar industry's carbon footprint is expanding rapidly, driven in large part by demand for energy-intensive air travel, researchers reported in the journal Nature Climate Change. 

International travel involving long-haul flights is among the fastest growing sectors, and could threaten efforts to reign in planet-warming carbon pollution. The total number of air passengers is expected to almost double by 2036 to 7.8 billion per year, according to the International Air Transport Association (IATA).

The study quantifies tourism-related global carbon flows between 160 countries. As in past decades, the United States is the single largest emitter of tourism-related carbon emissions, with other wealthy nations — Germany, Canada and Britain — also in the top 10. But burgeoning middle classes have moved emerging economies up the ranking, with China in second place. 

"We see very fast tourism demand growth from China and India over the past few years, and also expect this trend will continue in the next decade or so," said Ya-Sen Sun, a professor at the University of Queensland Business School in Australia, and co-author of the study.

Curbing the growing appetite for tourism and travel may prove difficult. "Behavior change from travelers — travel less, stay close to home, pay carbon offset — are found to be slow and marginal," said Sun. "Carbon taxes or carbon trading schemes can help to put extra pressure to speed the process."

A carbon pollution abatement that covered environmental costs, for example, would tack on an additional $425 (360 euros) to offset emissions from a round-trip flight from Sydney to London, the authors calculated.

fm/eg (AFP)