Carbon Offset Trading

As states like California show successful implementation of a carbon cap and trade program, it's a possibility that other states will adopt its policy moving away from carbon credits, like exist in the RGGI, and move towards carbon offsets. Do you see a formal exchange being created to sell carbon offsets? Research shows that these offsets are often ineffective, will there be a way to verify these offsets (such as being regulated by the SEC)? And could carbon offset based derivatives even be created? How far do you see the carbon offset market expanding in the next decade?