The argument isn't over about the utility of carbon offsets (although the various argumentative parties have since wandered off to other subjects), but my take is that, on balance, they do a little bit of good and -- more importantly -- train people to think in terms of the carbon footprints of their actions. Most of the offset providers, however, deal with the big impacts: a year's worth of energy, a trans-Atlantic flight, that sort of thing. But what about smaller purchases? How hard would it be to provide carbon offsets for one's everyday life?

Think of them as micro-offsets, in parallel to the various micro-finance projects underway across the developing world.

Micro-offsets offer a chance to do something big by doing something very small. Imagine a small amount -- say twenty-five cents to a dollar -- that could be added to the price of commonplace consumer products and services, from cheeseburgers to phone bills, in order to pay for a carbon offset. Importantly, such fees would be optional, but even a small amount would likely pay for more carbon than was actually produced by the product or service. The multitude of tiny amounts, added together, would be used to purchase traditional carbon credits, probably by an offset aggregator.

This idea is starting to appear in various forms. Chris Messina, for example, talks about "Carbon Offsetting Web 2.0," optional fees for web hosts and other web service providers, tacked on to (over-)pay for the carbon footprint of the energy used for the servers & such. Messina's idea demonstrates the utility of the micro-offset concept: by adding on to existing subscription services, consumers don't need to pay yet another bill; the price is low enough (Messina suggests around $1/month) that it's well within what a growing number of people would feel guilty enough to pay; and the offsets purchased by these fees enough to cover not just the server footprints, but ancillary carbon costs for the service providers. Imagine if Second Life -- or World of Warcraft -- made this kind of offer.

It's likely that online shopping systems of all sorts, not just subscriptions. would be simple platforms for micro-offsets; imagine every purchase at Amazon or eBay including a checkbox that reads, "Add $.50 to my bill for carbon offsets."

But if you're going to be tagging an extra amount onto the price of something to pay for its carbon, why not just institute a carbon tax?

Because no matter how useful such a scheme would be, there are few politicians willing today to stand up and say, "I want to impose a carbon tax!" The political will simply isn't there. That doesn't mean the social will isn't, however. We've seen plenty of examples of companies, communities and individual making decisions about environmental sustainability that go far beyond what Washington DC has been willing to do. Similarly, the existence -- and, hopefully, success -- of micro-offsets would be an existence proof that people are, in fact, willing to pay a bit more to shrink their carbon footprints.

Micro-offsets offer a bottom-up way to get people to pay more attention to their greenhouse gas impacts, and not just in the obvious, marketing-friendly shape of hybrid cars and compact-fluorescent bulbs.

The main downside of the basic micro-offset concept is that the offset cost is not tied to actual carbon impact; as a result, they don't provide the information transparency that would allow people to easily change behaviors. There's no reason why micro-offsets couldn't be linked to carbon impacts, of course -- once we get carbon labels that let people make informed choices. In the meantime, basic micro-offsets could still provide value. As they became more common, they would lead to both a small overall carbon footprint reduction, and a large step towards a carbon-conscious society.