Corporations and shoppers in the United States spent more than $54 million last year on carbon offset credits toward tree planting, wind farms, solar plants and other projects to balance the emissions created by, say, using a laptop computer or flying on a jet.
A Volkswagen program, offered in conjunction with Carbonfund.org, an intermediary, has sought to energize car sales.
But where exactly is that money going?
The Federal Trade Commission, which regulates advertising claims, raised the question Tuesday in its first hearing in a series on green marketing, this one focusing on carbon offsets.
As more companies use offset programs to create an environmental halo over their products, the commission said it was growing increasingly concerned that some green marketing assertions were not substantiated. Environmentalists have a word for such misleading advertising: "greenwashing."