Somebody at work asked me about a joke I made: that I was going to turn a profit on my cycling to work by selling the carbon offsets.

That led to a long digression about the nature of emissions trading and carbon offsetting (Al Gore was discussed), and I promised to write a little post about it.

As it happens, Wikipedia (surprise) has already got a very good article which would say most of what I was going to say as a primer on the subject.

All I'd add to that is if you're not sure what I'm on about, carbon offsetting is a way of compensating for the carbon-dioxide deficiencies of your current lifestyle by paying to have your actions "offset" by carbon-reducing activities (mostly tree-planting at the moment).

There's controversy about this for reasons of practicality, verifiability, efficacy, and even ethicality. The article has the details.

Indeed, my joke about selling my cycling commute was a joke on several of those issues: how can you tell if you buy my carbon offset that I won't drive to work anyway? How much does my commute really save, carbon-wise? Wouldn't I probably take the bus to work instead of my bike if I wasn't getting paid to offset?

Hey wait, don't I ride my bike regardless of whether I get paid or not?

In principle, I should say, the questions of verification is not long-term fatal. Eventually there will be sufficient certification in the industry to establish some reliable providers of the advertised service. The ethics of offsetting don't disturb me much. But I think evaluating effectiveness (and the right quantity to assign to the offset) is going to be a bit hard and forever controversial.

Just as a mostly silly example, how about I sell not my current offset, but the threat that I will start driving my car to work again? As long as I am sincere in my willingness to carry out the threat (and my willingness to not carry it out if I'm paid...), paying me for not doing so is functionally equivalent to any other carbon reduction.