The Waxman-Markey climate bill proposes more than a pure cap-and-trade scheme. It's actually cap and trade and offset. Offsets, put simply, would let polluters pump more carbon dioxide into the atmosphere than they would be permitted under the “cap” part of the program. Companies would earn that right by investing in projects in the United States or in other countries that reduce the amount of carbon dioxide being emitted into the atmosphere.

Grist takes a closer look at carbon offsets: Who wants them? How would they work? Would they help the United States reduce CO2 emissions?

Part 1: Key to climate bill, offsets have plenty of critics (Erica Gies)

Part 2: Offsets and Big Ag: Does the climate bill give away too much to the farm sector? (Erica Gies)

Sidebar: Pacific NW landowners team up to market forest offsets (Jessica Knoblauch)

Part 3: Offsets remain off-putting to many experts intent on curbing CO2 emissions (Erica Gies)

Sidebar: Biochar as the new black gold (Bill Hewitt)