Green house legislation is the distillation of political forces marshaled by science, economic foresight, activism, paranoia, the desire for change, leadership, sycophantalism, pleasure in moral whipping, settling scores, conservatism and those psychological forces which drive them. But in some countries we may accept the legislation as a given and turn our eyes the phenomena which flows from it but whose path to the sea is not yet clear:
In order to understand carbon offsetting we must first agree on what we accept for the sake of the argument. Here is a guess:
1. global warming is a problem
2. atmospheric CO2 significantly contributes to gobal warming
3. a reduction in increase of atmospheric CO2 now significantly reduces the effects of global warming in a meaningful time frame
4. atmospheric CO2 levels are substantially under human control
5. of the CO2 production under human control a significant quantity comes from human enterprize
6. reducing CO2 production is a cost effective means of addressing global warming relative to other means
I'm not sure I buy 6. but whatever. We are now tasked to reduce human emissions of CO2 although X may claim that there's a 7. lurking -- the continued moral fibre of individuals in the body politic. That's a more difficult question, which calls from great sympathy, but let us first work with what we can see clearly.
We have only two questions (a) is carbon offsetting effective? and (b) is it efficient compared to the alternatives?
Carbon offsetting by corporations is not motivated by moral considerations. It is motivated by legislation or self-regulation backed up by the threat of legislation.
It is effectively a tax on CO2 production, with the tax money going to industries that soak up carbon.
Now here comes the realpolitik beauty of carbon offsetting. CO2 producers favor it, since compared to outright bans and limits, taxes have greater flexibility and predictability. Hence fearing the whip of pending banning legislation, producers support this tax they would have normally hated. An increasingly powerful industry lobby group is created by those who take CO2 and the middlemen who find them. This lobby group is sees its interest as increasing the carbon transfer tax to the highest levels possible and to ferret our deception by CO2 producers! As an industry, it is a far more stable influence that the vagarities of popular political opinion. Even bureaucrats love it, as they now have their hands in another three industries.
Hence this is an effective real politic way of introducing, sustaining and increasing a cabon tax that would have great difficulties surviving as disconnected tax and grant system.
That answers (a). (b) remains an interesting question, as does what a clever realpolitik solution would look like for funding those alternatives.
If we have a serious problem, we are tasked to re-engineer the world using the best political, psychological and technological tricks we can come up with.