For the individual citizen, climate change can seem overwhelming. How can one person make a difference? There are ways, though, like carpooling and swapping out incandescent light bulbs for fluorescents. And now another option is available–the climate change credit card.

“Affinity cards”–credit cards that support a green or social cause–have been with us for many years. Affinity cards with a global warming focus are relatively new, though. Lately there’s been a boomlet in these offerings–hardly a surprise, given climate change’s rapid rise to public prominence.

Broadly speaking, climate-change affinity cards offer three options. First, people can automatically have the carbon impact of their credit card purchases offset. Rabobank, a Dutch financial institution, takes this approach with its Rabocard. It calculates the carbon cost of the purchases people make with this affinity card and then contributes that amount to climate projects whose quality has been verified by the World Wildlife Fund, a highly-regarded environmental group. The Rabocard is currently available only to Dutch customers, but it’s an ingenious idea that’s likely to migrate elsewhere.

Another option is to give credit-card holders the option of applying their reward points to green power initiatives. This is the approach Wells Fargo and HSBC take. It’s a great concept as far as it goes, but it only goes so far. I’ve never redeemed a credit card reward point, and I suspect there are a lot of people like me. It’s usually a harmless enough form of inactivity–I only hurt myself, after all–but here it neutralizes the affinity card’s climate-change component.

Finally, there are credit cards that automatically contribute to climate-change projects whenever a customer uses it to make a purchase. In so doing, it does away with the need for consumers to proactively direct rewards points to climate projects and is correspondingly more effective. Examples include:

1. GE’s Earth Rewards card, which invests 1 percent of credit-card purchases in carbon offset projects. (Alternatively, consumers can take a ½ percent rebate with the remaining ½ percent dedicated to carbon offset projects.)

2. The Brighter Planet Visa card, which is offered through Bank of America. Under this program, every dollar spent in credit-card purchases generates one EarthSmart™ point. These points are then aggregated and applied to climate projects, with 1,000 points equaling an estimated one ton in carbon offsets. For every two base points earned through December 2008, Bank of America is contributing one additional EarthSmart™ point.

How much impact can climate-change credit cards have? More than you might expect. The average American makes more than $12,000 each year in credit card purchases. If half of these expenditures were made using the Brighter Planet Visa card, it would be the equivalent of taking an average car off the road for one year. With Bank of America’s matching grant, it would also cover the carbon cost of heating and cooling an average home for one year.

Some people believe you can’t spend your way past the climate-change crisis. They’ve got a point. Less is more where protecting the planet is concerned. The reality, though, is that while we may reduce our consumption, there’s no way any of us are going to stop consuming completely–not till we’re dead, anyway.

So long as we’re consuming, why not do what we can to reduce the carbon impact of our purchases? While climate-change affinity cards are only a piece of the puzzle, they’re a potentially important one–and a painless and effective way to tread more lightly on the planet.

Carl Frankel is a journalist and author who specializes in green business, green products, and integral living.