For energy companies willing to accept some limits on warming gases, one goal is to firm up a market for
tradeable credits earned by companies that make sharp cuts in
emissions or plant or protect forests, which absorb carbon dioxide.
Companies could buy and sell
credits among themselves, and could satisfy up to 15 percent of its
emission reduction requirements by submitting
tradeable allowances from another nation's market in greenhouse gases, or by contributing to projects that sequester carbon dioxide
emissions.