We've all heard the scary statistics about the climbing rates of carbon dioxide emissions from human activities. But let’s imagine, just for argument’s sake, that we agreed to limit emissions of the heat-trapping gas to the quantity that the world’s forests and oceans can absorb each year. Assuming equal distribution of “polluting rights” among all 6.5 billion people on earth, each of us would be allowed a maximum of 6,600 pounds of CO2 emissions per year. That sounds like a lot until you do the math. You’ve probably got a refrigerator, right? That will cost you 220 pounds each year. Those 20 miles you commute each day? Subtract 4,400 pounds from your budget. Taking a flight from New York to Costa Rica to hug some trees in the rainforest? Uh oh. That’ll be 4,000 pounds. Game over! 

Or is it? When the name of the game is global warming, there’s little doubt that we are only starting to pay for a pattern of consumption that stretches back to the dawn of the Industrial Revolution. Atmospheric concentrations of CO2 have been rising steadily in recent years. And while many human activities, particularly driving, release CO2 into the atmosphere, air travel is a noteworthy culprit. Some climatologists say that aircraft emissions such as nitrogen oxides exacerbate the heat-trapping qualities of CO2 when they’re released at high altitude — say, from a jet engine at a 30,000-foot cruising altitude. 

For those who wish to make amends for their jet-setting habits, a growing number of organizations sell peace of mind in the form of carbon offsets. With the help of online calculators, you can estimate the amount of CO2 your air travel would generate, and then match this figure to the financial support needed to subtract an equivalent amount of CO2 from the global equation. American Forests, for example, can remove an estimated 5 tons of CO2 from the atmosphere each year with every acre of trees it plants. Other companies sell offsets to provide funding for renewable-energy projects or energy efficiency initiatives.

For some consumers, buying offsets has proven to be a handy way of evening the score. Steve Greenberg, an energy management engineer at the Lawrence Berkeley National Laboratory in California, recently purchased about $300 worth of offsets from the Bonneville Environmental Foundation after attending a six-person family gathering in Edmonton, Alberta, with a side road trip to nearby Jasper National Park. He and his wife also spent “a sizeable chunk” to offset the flights that the entire wedding party took to their nuptials in 2002. “Offsetting assuages our guilt,” he admits, though the couple’s use of rooftop solar panels to generate household electricity and power their electrical car would seem to place them above reproach. “It’s an additional lever we can pull to move the economics and production of electric power in the right direction.” 

Though buying offsets is appealing in theory, some environmental advocates wonder if they deliver the benefits promised, while others question the wisdom of letting consumers sidestep the remorse that unsustainable choices should entail. Dan Becker, director of the Sierra Club’s global warming program, concedes that these initiatives can raise awareness about the environmental impact of flying and other lifestyle choices.But, he warns, “we need people to cut their pollution. If buying offsets makes people feel less guilty about their polluting ways, our children lose out.”

Others disagree. Mitch Rofsky, cofounder of Better World Club, an auto club similar to AAA that offers travel-related carbon offsets, points to improvements his company has made to public schools in Portland, Oregon, with offsets purchased by green-minded customers — including the installation of occupancy sensors to switch lights off when a room is empty and new, efficient natural-gas furnaces in place of oilburning models. Rofsky doesn’t believe that everyone who buys offsets does so to excuse high-polluting lifestyles, although some people may fall into that category, he concedes.

Judging the value of various offset projects is a bit tricky. Better World Club’s projects have been certified by the Climate Neutral Network, a team of consultants that helps consumers evaluate the quality and duration of their green investments. But not all projects have been reviewed by independent groups, and because the United States did not ratify the Kyoto Protocol, efforts to establish federal regulatory boards or rating criteria have yet to be developed. In most cases, consumers will have to rely on their consciences and judgment when choosing which programs to support. There are signs, though, that these decisions will get simpler in the future. Recent pledges from more than 200 U.S. mayors and a coalition of seven Northeastern states to limit greenhouse gas emissions raise hopes that local efforts can make broader ones more feasible.

“We need new regulations that get the worst-performing products out of the marketplace and drive investment in new, better incentives for cleaner technologies,” says Dale Bryk, an attorney overseeing state climate policy for the Natural Resources Defense Council. “But that doesn’t mean that there’s nothing we can do until we get there.” Bryk stresses supporting CO2 reductions beyond existing measures, as well as thinking critically about how offset funds are used: Reforestation projects may be risky, for instance, because planting one tree might justify cutting down another elsewhere.

Whether or not you buy offsets for your rainforest vacation, the most important thing you can do is look for ways to put your daily transportation strategies on a carbon diet. Telecommute and take public transportation to work when possible. When traveling long distances, take a train instead of a commuter flight, or combine business and vacation itineraries into a single trip. After all, there are many ways to have a bon voyage.

Story by Jenny Gage. This article originally appeared in Plenty in July 2006. The story was added to MNN.com.

Copyright Environ Press 2006.