In the middle ages, the Catholic Church developed the practice of granting indulgences. The idea of an indulgence was this, you had committed a really bad sin ( i. e. a mortal sin) like cheating on your wife or stealing money, not something trivial. You had confessed your sin and received absolution. But the priest thinks that now you need to do penance. Penance can be something small, like saying the rosary 50 times or something big like walking on your knees to the nearest saint's grave. Penance is imposed for the good of your soul not just punishment. You are supposed to develop a change of heart because of the penance. The thing was that penances could be pretty rough, so the church began to allow people who were old or disabled or otherwise unable to pay someone else to do the penance. This system rapidly degenerated into the indulgence system where you just paid your way out of the penance. As so often happens with well meant penalties (think cigarette tax) the stream of money generated by the penalty (which penalty is meant to discourage the bad behavior) becomes so attractive that the original purpose is lost. The church began to depend on the money generated by the indulgences. The whole system came to a halt when Martin Luther objected. His trenchant observations about the pope, the pope's jurisdiction over purgatory, and the primacy of the Gospel to Christian belief spread like wildfire, igniting the reformation.
Carbon credits are really just like indulgences. In the new religion of global warming, exhaling too much carbon dioxide is sinful. But you can buy your way out of an anemic electric car and living in the dark by buying carbon credits. Carbon credits are like indulgences. They allow you to pretend to care about your new creed of low carbon emissions while simultaneously creating enormously more carbon dioxide than anyone else. Even left leaning Snopes.com admits, for example, that Al and Tipper Gore use about 12 times as much electricity as the average American home.
Those of us who are not devotees of the new environmental religion see the whole thing as ridiculous. Because it is.