rationalskepticism.org

Carbon offsets might have been a good idea ten or twenty years ago, as a means of flattening the curve while better solutions were found, but we're pretty much beyond piecemeal, band-aid solutions now, because the climate is a gaping wound. They could conceivably have slowed AGW sufficiently to buy us a few decades of research into carbon-neutral energy. As it is, they're little more than gesture politics.

Better than nothing is about the best you can say about them.