So, the debate on carbon offsetting was very interesting. It turns out there are a lot of very difficult problems judging whether a particular scheme is effective or not. On the other hand, an effective scheme can be a far more effective way of spending money on saving carbon emissions than some ways of trying to cut your own emissions.
What annoyed me was the academics arguing that, because we can't be certain about carbon offsetting, and because it might make people complacent about their own emissions, we shouldn't do it at all. And this from a guy who's flying to China to talk about global warming. Talk about hypocrisy!
My conclusions were:
1. Save on your own emissions where it's clearly free or economic to do so.
2. Where the economics of saving emissions are doubtful, think about offsetting instead.
3. Where you can't save on emissions (hey, we all have to eat something!), then definitely offset those emissions.
4. When offsetting, offset more than your own emissions. Maybe double or treble the offset, if you can afford it.
5. Look quite carefully at the particular scheme you're investing in.
A good offset scheme should make an investment in some low carbon technology. That technology should not be the cheapest available for the job, otherwise the investment would have happened anyway. Alternatively, look for a well managed reforestation scheme.
I've not managed to find a site that reviews offset schemes, or even lists many of them. If you know of one, please comment below!