"On Friday, the Environmental Protection Agency is expected to give a price tag for the Senate's global warming bill. That will frame next week's scheduled debate on the legislation.

One key part of the climate bill has to do with fuels made from green plants. These can reduce the use of fossil fuels, and they also are a big draw for farm-state votes.

But scientists writing in the current issue of Science magazine point out a huge error in existing biofuel laws that could actually make climate change worse. They say these rules inadvertently encourage deforestation, which in turn contributes to global warming."