The idea of offsetting carbon emissions is sound in theory, if not yet in practice.
The sale of indulgences by the Catholic church in the early 16th century, whereby people could, in effect, purchase forgiveness of past sins by handing over enough money, was condemned by Martin Luther and other reformers. Today, some environmentalists are denouncing the "offsetting" of carbon emissions in similar terms. A company that wants to declare itself "carbon neutral" calculates how many tonnes of carbon it emits, and then offsets the emissions by paying someone else not to emit that amount of carbon on its behalf. Just as Luther criticised indulgences, critics of offsetting argue that the ability to buy retrospective forgiveness for sins of emission is no substitute for not sinning in the first place.



