For those who want to see the planet but fret about the harmful environmental effects of driving and flying, a growing list of companies are offering a chance to "offset" the journey.
They're called carbon offset programs, and they aim to reduce the threat of global warming that scientists say are caused by greenhouse gases emitted when burning fossil fuels. Using the offset programs, most available online, travelers can calculate how much carbon dioxide their trip produces and pay to generate an equal share of renewable energy such as wind or solar power.
There are dozens of the companies, some for profit and some nonprofit that have proliferated mainly during the past two years to offer the service. They provide a host of options and cost anywhere from $5.50 to over $18 to offset one ton of carbon - about equal to a cross-country flight.
There are skeptics of such programs and they are not just those who question the impact of global warming. The nascent industry is unregulated and there is not yet one accepted set of standards for these businesses, making it difficult for consumers to confirm whether all the companies are doing what they claim.
Some businesses that sell the service do not disclose how much money they keep in administrative costs or how they are calculating pollution. Some environmental groups even say the offsets do little to encourage people to conserve energy.
Global warming has generated more discussion of late, with the success of Al Gore's documentary, An Inconvenient Truth, and a recent report from a United Nations panel that says rising temperatures are causing more extreme weather and rising sea levels.
That report said some coastal areas like Baltimore's Harborplace could potentially be underwater at high tide by 2100.
The attention has helped the offset programs gain enough mainstream interest that major travel sites Travelocity and Expedia both began offering the products to their airline customers.
Expedia partnered in August with TerraPass, which funds several programs. It said its customers have paid to offset almost 27 million pounds of carbon, equal to flying from Baltimore to Los Angeles about 10,000 times. Travelocity teamed with the nonprofit Conservation Fund, which plants trees, and its customers offset about 10.4 million pounds in the last four months of the year.
The niche market for these services may face a hurdle in growing larger since some travelers may not be willing to add more to the price of a plane ticket, for example. Consumers already pay extra for taxes, airport facility fees and post-2001 security costs. But those selling offsets insist that customers don't view these services as a tax but as a separate purchase to benefit the environment.
Jeff Siegel, a Baltimore publisher, came across a TerraPass and decided it was an easy way to do his part. He paid $10 to offset emissions from a Caribbean trip he plans in April.
"TerraPass simply gives eco-minded people another option," Siegel said. "For example, there are certain hybrids on the market that can drastically reduce our fuel consumption. But they aren't cheap. Not yet, anyway. And if you can't afford a new hybrid, but you want to try to do something to offset your car's emissions, this is an excellent way to do it."
TerraPass was founded in 2004 as a class project for an environmentally conscious professor at the University of Pennsylvania's Wharton School of Business. It's now a for-profit company, and mostly within the past year has signed up more than 2,400 members and reduced 36 million pounds of carbon - the equivalent of taking almost 6,000 cars off the road - by funding nine renewable energy projects.
It funds wind farms. It buys and retires credits on the Chicago Climate Exchange, a voluntary system where companies reduce their emissions and sell the credits to companies that don't. And it funds biomass programs that capture methane from cow manure and burn it. That puts a renewable energy source into use and keeps methane, itself a greenhouse gas, from entering the atmosphere, the company said.
"We wanted to make it so many people could participate," said Tom Arnold, chief environmental officer for TerraPass, which is based in San Francisco. "By aggregating a large number of individuals together, you can get a year's worth of carbon reduction for your car for about $50. A cross-country flight is about $10."
TerraPass may become one of the better-known programs because it hands out stickers and luggage tags to its customers. But there are many offset options of varying quality, according to a review in January of 13 programs done by the Tufts Climate Initiative, which is Tufts University's center for studying climate change.