Allison Linn Senior writer • Profile • E-mail

When Al Gore faced attacks earlier this year over how much energy is used to power his 10,000-square foot home, the vice president-turned-global warming guru offered an increasingly common defense.

Gore may indulge in some of life’s luxuries, but a spokeswoman told The Associated Press that Gore still maintains a “carbon-neutral” lifestyle. That’s thanks to a mixture of conservation and carbon offsets — a voluntary system in which people pay money toward renewable energy projects as a way to counterbalance their use of more traditional, and polluting, energy sources.

The desire to make amends for everything from a trip to the Oscars to a morning commute has spawned a plethora of for-profit and nonprofit carbon offset providers, whose offerings run the gamut in terms of how much they cost and what they say they will accomplish. But the growing retail market, which is largely unregulated, also is raising questions among environmentalists who say not all offsets are created equal.

“There’s a lack of standards in the voluntary market, and the offsets that people are purchasing might not be accomplishing what they hope they will,” said Deborah Carlson, climate change campaigner with the David Suzuki Foundation, a Canadian environmental advocacy group.

When the environmental group Clean Air-Cool Planet commissioned a study on carbon offsets, communications manager Bill Burtis was surprised to find how few groups offered transparent details of their projects or had set up any process of independently verifying their environmental benefits.

“It was pretty startling,” he said.

Some offset retailers did not even return the study’s questionnaire, and one provider, which Burtis wouldn’t identify, actually lobbied against the release of the report.

Clean Air–Cool Planet hired an independent firm to do the study because it has ties to a carbon offset provider called NativeEnergy.

The study ultimately awarded only a few companies its highest rankings, including the U.S. firms Climate Trust, Sustainable Travel International and NativeEnergy. Burtis said other providers have made changes since the report came out.

There also have been attempts to come up with formalized criteria for ranking carbon offsets, but no clear standard has emerged. That process, too, could incite controversy — Burtis notes that whoever ultimately creates a solid standard could potentially make a lot of money off validating other groups’ carbon offset projects.

Environmentalists are quick to note that carbon offsets do have the potential to do good. Carlson said one major benefit of carbon offsets is that they often force people to evaluate how much carbon they actually are responsible for, hopefully spurring people to first make reductions and then buy offsets. It’s also seen as a practical way to fund renewable energy projects ranging from wind power to solar energy.

But others worry that an easy payment solution has the potential to give people a way to essentially assuage guilt over buying big cars, big houses and even Big Macs, while doing little to actually reduce their “high-carbon” lifestyles. Carbon offsets may counterbalance your use of polluting energy sources, but they do not actually erase the initial output that contributes to global warming.

MORE FROM TECHNOLOGY & MONEY

Technology & Money Section Front

What a mess! 5 financial cleanup tips Heavy load? Best backpacks for kids Money 911: What’s your emergency? Pinching pennies like your grandparents Pinching pennies like your grandparents Mattel awarded $100 million in Bratz lawsuit A good find: GPS to locate the kids Survive the drive! Great gear for kids Need some cash? Don’t raid your savings The PC gets more personalized Technology & Money Section Front   Add Technology & Money headlines to your news reader: