Planting trees (or paying to have them planted) offsets one’s emissions by directly absorbing CO2. Buying blocks of renewable power from your power company actually reduces (not offsets) your CO2 emissions by ensuring that power they buy is from non-CO2-producing sources. Paying to develop renewable sources of elecricity here in the U.S. offsets CO2 emissions by reducing the grid’s dependence on coal. Then there’s the morally offensive offset of paying someone in another country to reduce CO2 emissions so you don’t have to.

As you know, I’m a firm believer in reducing CO2 emissions– my wife and I have cut ours by over 50%, and I believe almost everyone could cut theirs in half with very little effort. But when the reduction is done, offsets can play a logical and significant role in addressing the remaining emissions. We’ve offset all of our remaining household emissions, and about 40% (so far) of the 12 tons of CO2 emissions the U.S. economy makes on our behalf. And none of it is by paying someone far away to do what we’re not willing to do ourselves.