...Tony Blair had exhausted his capacity to disappoint, along comes this.
Update: I admit to being confused about offsetting. I saw someone compare it to trying to combat sea-level rise by drinking more. But summing up what I've read recently, it seems that it's better not to emit at all (so flying's not ok), but that some projects can help. This piece from the Independent sets out the pros and cons quite nicely. And this from Nature($) goes into a bit more detail. The basic message is energy efficiency and renewable generation, good, trees, bad.