The world's domestic and international tourism industry contributes to eight per cent of the global greenhouse gas emissions - about four times greater than previously estimated - scientists, including one of Indian origin, have found.
Small islands attract a disproportionate share of carbon emissions, considering their small populations, through international arrivals, while the US is responsible for the majority of tourism-generated emissions overall, the study found.
The team led by researchers at the University of Sydney in Australia found the global comprehensive tourism footprint of tourism-related greenhouse gas emissions is about four times greater than previous estimates, is growing faster than international trade and is already responsible for almost a tenth of global GHGs.
The researchers recommend financial and technical assistance could help share burdens such as global warming on winter sports, sea-level rise on low-lying islands and pollution impacts on exotic and vulnerable destinations.
The complex research took a year and a half to complete and incorporated more than an estimated one billion supply chains and their impacts on the atmosphere.
"Our analysis is a world-first look at the true cost of tourism - including consumables such as food from eating out and souvenirs - it's a complete life-cycle assessment of global tourism, ensuring we don't miss any impacts," said Arunima Malik, corresponding author of the study published in the journal Nature Climate Change.
"This research fills a crucial gap identified by the World Tourism Organization and World Meteorological Organization to quantify, in a comprehensive manner, the world's tourism footprint," said Malik.
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"Given that tourism is set to grow faster than many other economic sectors, the international community may consider its inclusion in the future in climate commitments, such as the Paris Accord, by tying international flights to specific nations," said Ya-Yen Sun, from the University of Queensland.
"Carbon taxes or carbon trading schemes - in particular for aviation - may be required to curtail unchecked future growth in tourism-related emissions," Sun said.
The study found air travel was the key contributor to tourism's footprint and that the carbon-intensive industry would comprise an increasingly significant proportion of global emissions as growing affluence and technological developments rendered luxury travel more affordable, said Manfred Lenzen, lead researcher from the University of Sydney.
"We found the per-capita carbon footprint increases strongly with increased affluence and does not appear to satiate as incomes grow," Lenzen said.
Previous research has quantified the carbon footprint of specific aspects of tourism operations such as hotel, events and transportation infrastructure; and in particular countries or regions.
The study included 189 individual countries and all upstream supply chains.
The US tops the carbon footprint ranking, followed by China, Germany and India. The majority of these carbon footprints are caused by domestic travel; business travel could not be distinguished from tourism.
In countries such as the Maldives, Mauritius, Cyprus and the Seychelles, international tourism represents between 30 per cent and 80 per cent of national emissions.
The researchers found that international arrivals and tourism receipts have been growing at an annual three percent to five per cent - outpacing the growth of international trade.
The study found tourism is forecast to grow at an annual four per cent - outpacing many other economic sectors.
Between 2009 and 2013, tourism's global carbon footprint increased from 3.9 to 4.5 gigatonnes of equivalent carbon dioxide - four times more than previous estimates - accounting for about of global greenhouse gas emissions. Transport, shopping and food are significant contributors.