Counting ALL the carbon in climate policies

One of the most difficult challenges in curbing greenhouse gas emissions is recognizing that CO2 emissions are influenced by more than fossil fuel consumption. About 20 percent of excess carbon emissions come from deforestation. Trees and plants breathe CO2, and that can make a big difference.

If we ignore this, corn-based ethanol might look climate friendly. If we account for it, we're better off using gasoline, at least when it comes to total carbon emissions. This was an important point made by Searchinger et al. in Science last year. Ethanol production drives up commodity prices, which encourages farmers to clear forests to plant more crops. One could argue with some of the details of Searchinger, but the overall conclusion is hard to dismiss.

If we can price carbon sequestrations as well as carbon emissions, and make it global, everything works out fine. If we don't price carbon sequestered from trees and plants, then emission reductions in one place might slip out somewhere else. Like squeezing a balloon.

Whether we use taxes or a cap-and-trade system, this is going to be one of the messy details that needs to be sorted out. It will be hard enough counting and pricing fossil fuel use. Counting and pricing carbon in agriculture and forestry will be much harder.

Here is Ruben Lubowski, a good friend and coauthor of mine, testifying before the Senate on "carbon offsets" about 8 months ago. He's on a 2-year leave of absence from USDA working at the Environmental Defense Fund.