I had an interesting conversation with my father-in-law this week about carbon credits. There are organizations out there that are selling credits for carbon dioxide—credits that regular people like me could and should buy.

Here’s how it works: Figure out how much CO2 you are personally responsible for. You can use a variety of calculators to help you figure this number. I used the Wired magazine Carbon Quiz to figure that my lifestyle generates 15 tons of CO2 per year.

Now here’s what I can do about it: I can buy a credits for that.