The author of today's post, Sheryl Canter, is an Online Writer and Editorial Manager at Environmental Defense.

Carbon offsets are a good idea that, unfortunately, without guidelines, can be implemented badly. The basic idea is to reduce and then offset the carbon emissions produced by your lifestyle by funding projects that reduce carbon emissions elsewhere. This works because, from a global warming perspective, it doesn't matter where the carbon comes from. A reduction anywhere reduces the global total.

But how do you know a given offset is truly reducing carbon emissions?

Selling carbon offsets has become big business, but it's an unregulated business, and it can be a time-consuming challenge for an individual to evaluate whether a given offset is legitimate. Last month Rep. Edward Markey (D-Mass.) asked the Federal Trade Commission (FTC) to look into the carbon offset market and consider setting standards. This week FTC chair Deborah Platt Majoras agreed to do just that.

Today's front page article about offsets in the Washington Post mentions an important area of confusion beyond the simple danger of fraud: renewable energy certificates or RECs. These sound like offsets but they're not, because without clear rules regarding ownership, the same emissions reductions could be double-counted or sold multiple times.

Environmental Defense has established criteria for valid offsets, and we provide links to high-quality projects that meet our criteria. But ultimately what's needed is government regulation, and it looks like that finally will happen.

*The links in the last paragraph were updated on Sep 25, 2008.