Two weeks ago, I wrote about a letter written to CARB by a group of scientists calling on CA to at least temporarily ignore global warming emissions from indirect land-use change when looking at biofuels. On July 2, Tim Searchinger wrote a response (PDF) correcting one important mischaracterization of his work and taking issue with the fundamental recommendation in the group's letter. I agree with Tim's ultimate concern with this recommendation:

Lifecycle analysis of biodiesels from palm, soybeans and rapeseed tend to calculate large greenhouse gas benefits if you ignore land use change. Your advice would therefore have California promote one of the world’s most destructive agricultural practices. That would undercut biofuels that hold promise by avoiding or minimizing impacts from land use change.

The whole letter is definitely worth a read if you want to understand Tim's basis point in some detail.