Before you pay others to reduce their emissions on your behalf, you need to do everything reasonably possible to reduce your own emissions first. As the saying goes, “Physician, heal thyself,” before presuming to heal other people.
The whole point of offsets is not to make you feel good, and it’s not to allow you to continue polluting as much as you want (by, say, supporting new coal plants or other dirty forms of power). Offsets are cheap and in some sense bastardized emissions reductions (more on this in a future post).
In general, the point of offsets is to reduce greenhouse gas emissions, and specifically to allow you to offset any emissions that are left over after you have cleaned up your own act — or to offset emissions from one-time events such as concerts.
While the other rules apply to offsets themselves, and thus can be independently verified in a fairly rigorous fashion, this rule applies to a whole range of polluting activities a company or person can take part in, and requires a judgment call. What is “everything reasonably possible”?