Environmentalists who love to travel (myself included) aren't going to want to hear this news, so I'm not going to sugar-coat it: travel, according to a new study, generates about four times as many greenhouse gases as previous estimates have indicated.

Why the big change? Because for this new study, Dr. Arunima Malik from the School of Physics at the University of Sydney and her team looked at more than just carbon dioxide emitted from transportation like planes and cars to calculate impact.

In addition to transport, the researchers took into account shopping and food, which were also "significant contributors," to greenhouse gas emissions, according to the paper. Inputs from hotels and other accommodations were taken into consideration as well. "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," Malik told Phys.org.

The research, published in the peer-reviewed journal Nature Climate Change, looked at 160 countries' travel inputs and outputs. Malik and her team incorporated so much information that it took over a year to gather and calculate it all to understand the complete supply chain involved in travel and tourism.

The number-crunchers estimated that between 2009 and 2013, the total carbon footprint of travel grew from 3.9 billon metric tons of CO2 to 4.5 billion metric tons each year. That's about 8 percent of the world's total greenhouse gas emissions.

The United States tops the carbon footprint ranking, having produced almost a billion tons of CO2 in 2013 alone. The U.S. was followed by China, Germany and India. "The majority of this footprint is exerted by and in high-income countries," the study's authors wrote. That included a majority of U.S. travelers staying within their borders and for international travel, from people moving from one wealthy country to another.

Your choices matter

Tourism is a rapidly expanding industry, growing faster than international trade, so numbers of travelers and miles traveled per person are expected to keep increasing.

What are the solutions to reducing impact if you love to travel? Vacationing closer to home is one simple way to cut emissions. (Let's bring back the summer lake vacation!) You can always refuse housekeeping when you stay at hotels, or better yet, seek out smaller, family-run eco-friendly accommodations. Use public transportation instead of renting a car, and pack light.

And how about budgeting in some carbon offsets, too? "To make my own travel more sustainable — for future generations — I invest in long-run abatement options at prices that incorporate at least average abatement costs, like investing in afforestation, rather than assuming only low-hanging fruit, like residential power efficiency," lead researcher, University of Sydney professor Manfred Lenzen, told Phys.org. For flying from Australia's east coast to England, he would pay $425 to offset emissions — a significant sum.

The study raises questions we should all think about, like what's the true cost of climate change on future generations? Greenhouse gases exacerbate climate change, which not only melts glaciers, flooding low-lying islands and shores, but also eliminates the habitat of already endangered animals and leads to more insect-born diseases.

What's avoiding that worth?

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.