Free Republic

In the late Middle Ages, professional pardoners sold indulgences to Roman Catholic parishioners with the promise that their sins would be forgiven. It was one of the practices that led to the success of Martin Luther's Reformation. Today, some environmentally conscious people purchase so-called carbon offsets to compensate for the CO2 emissions they are personally responsible for. ...At least 50 companies sell offsets for air travel for between $5 and $30 per ton of CO2. Some of them sell offsets for other activities as well.

You can neutralize the rest of your pollution—through offsets. When you buy offsets, you essentially pay someone to reduce or remove global warming pollution in your name. For example, when you buy 10 tons of carbon offsets, the seller guarantees that 10 fewer tons of global warming pollution go into the atmosphere. While the pollution you produce yourself is the same, you get the credit for that 10-ton reduction.