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LISA NAPOLI: For the first time in over 20 years, we're using less oil than ever. The numbers from the International Energy Agency show consumption is down, but down is relative — under a percentage point. Britain says it's going to hawk the practice of paying someone else to make cuts in CO2 equal to your own emissions. The market for carbon trading schemes has exploded. From the Marketplace Sustainability Desk, Sam Eaton says whether they actually reduce greenhouse gas emissions is another story.

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SAM EATON: Britain will become the first country to impose a national standard for CO2 offsets. It plans to adopt Kyoto-style restrictions for voluntary carbon trading.

Mark Trexler, with Trexler Climate and Energy Services, says similar efforts are underway here in the U.S. And for good reason.

MARK TREXLER: There're a lot of well-meaning people, but not all of them necessarily understand what this market is about. So you're seeing things done of widely varying quality.

In other words, there's little guarantee that the carbon offsets businesses and consumers buy are reducing greenhouse gas emissions.

But Trexler says the U.K.'s heavy-handed restrictions for the voluntary market could backfire.

He says the move will likely double or triple the cost of those offsets, discouraging what he calls the market's most valuable asset: encouraging consumers to think about their personal contributions to global warming.

In Los Angeles, I'm Sam Eaton for Marketplace.