Carbon offsets are a good idea, but it's hard to know whether a given project truly reduces carbon emissions. There are no unified standards. To help you make good choices, Environmental Defense Fund has just published CarbonOffsetList.org, a guide to high-quality offset projects for businesses and consumers. These are projects that we would turn to for our own offset needs. Check it out!

This post is by Sheryl Canter, an online writer and editorial manager at Environmental Defense Fund.

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.

Carbon dioxide (CO₂), while not the only greenhouse gas, is the most abundant. CO₂ is emitted into the atmosphere when we burn fossil fuels, and most of the energy in this country comes from burning fossil fuels. Thus, anything that requires energy to manufacture, transport, or operate causes the emission of CO₂ (see my previous post, The Carbon Footprint of… Everything).

A "carbon footprint" is the amount of CO₂ released by an activity or entity. So what's your carbon footprint?

It's difficult to make an exact calculation because the carbon footprint of so many things is unknown – for example, the amount of CO₂ emitted in the manufacturing of your shoes. But the basics are known, and can give a very good picture of how your choices contribute to global warming. The kind of home you live in, how much you drive, and how often you fly can account for half a person's carbon footprint.

You can calculate your carbon footprint for these three main elements on our Web site. You enter basic information about your lifestyle, and we take it from there. After the calculation, the site describes how you can minimize or offset your emissions – smart heating and cooling, smart use of appliances, smart driving, switching to compact fluorescent light bulbs, and selecting offsets.

Here are some statistics to think about:

• The average American car emits seven tons of CO₂ per year.
• The average American person emits 20 tons of CO₂ per year.
• The United States emits 7 billion tons of CO₂ per year.
• The world emits 30 billion tons of CO₂ per year.

If you're confused by the notion that gases like CO₂ have weight, check out my earlier post Picturing a Ton of CO₂.

ignoratio elenchi n.
A logical fallacy of presenting an argument that may in itself be valid, but has nothing to do with the proposition it purports to prove. Also known as "irrelevant conclusion". [Lat. ignorance of refutation.]

Al Gore's response to charges of being an energy hog was that he buys carbon offsets to neutralize his carbon emissions. This sounded bogus to a lot of people, but in fact it's not.

The concept of carbon offsets is simple. If your lifestyle uses a lot of energy and you like the way you live, you can still reduce your carbon footprint by funding the negation of carbon emissions elsewhere. Carbon offsets work because the source of CO₂ doesn't matter – only total CO₂ in the atmosphere matters.

This isn't clear to everybody. "Another stab at carbon offsets" on Economist.com argues that it's illogical to say, "I am pouring tons of carbon into the air with my transportation needs, so I will therefore . . . increase the supply of electricity in Kansas." Yes, that's illogical, but it's not what carbon offsets do! Carbon offsets wouldn't increase the supply of electricity in Kansas, they would reduce carbon emissions in Kansas.

"A tale of two markets", also on Economist.com, argues that buying offsets doesn't work because some offsets don't deliver what they promise. It's true that some offsets don't deliver, but many do. That said, you do need to make a careful choice when buying offsets. To help you evaluate, Environmental Defense has established criteria for valid offsets, and we provide links to portfolios of high-quality offsets that meet our criteria.

One other thing to note… Some investments that are good for the climate do not strictly qualify as offsets. For example, some energy companies sell "Green Certificates" or "Renewable Energy Certificates" (RECs) – money you give to the power company for investment in clean energy. Encouraging investment in green technology is good, but doesn't offset your emissions because there is no direct link between your purchase and the power company’s purchase of clean energy.

In addition to misinformation, the news is swimming with Ignoratio Elenchi arguments against carbon offsets. "The Corporate Carbon Offset Craze" argues that buying offsets can't work because it's so easy to do. Huh? "The Carbon Neutral Myth?", discussing a report from Carbon Trade Watch [PDF], argues that buying offsets encourages energy use by assuaging guilt. If buying offsets assuages guilt, it's because it works. And there's no reason to think that people would conserve more if carbon offsets weren't available. If people don't want to make a big effort and buying carbon offsets is easy, then how great that it's an option!

But this week’s Ignoratio Elenchi Award goes to the Wall Street Journal for "An Inconvenient Pool", which argues that carbon offsets don't work because not everyone can afford to buy them. First of all, most middle class Americans can afford to buy offsets, but regardless – there's no reason why everybody has to buy offsets for them to work.

The going rate for offsets in the U.S. is about $4 per ton. Since the average family emits 24 tons of CO₂ per year, most of us can become climate neutral for about $100 per year – that's 27 cents a day.