Obama is essentially impotent without Congress.
Brookings concludes:
Only Congress really has the power to implement the fundamental regulatory and fiscal changes—such as carbon taxes or broad-based energy policy—that would put the U.S. on an aggressive path toward a low-carbon pathway. As such, Obama’s strategy is best seen as a push to keep us close enough to that pathway so that, if Congress does choose to implement some more substantive measures, the costs of making the transition will be relatively moderate, particularly compared to the likely damages from climate change.