In an interview with Yale Environment 360, Amory Lovins, co-founder and chairman of Rocky Mountain Institute, says that world's biggest untapped energy source is efficiency. And retooling for energy efficiency will require "barrier-busting" at many levels. And government, Lovins says, "should steer, not row."

As he assumes the presidency, Barack Obama must make climate-change legislation and investment in green energy top priorities. And he must be ready to take bold — and politically unpopular — action to address global warming.

The next U.S. president should not wait for Congress to act on climate-change legislation. Instead, he should make use of the Clean Air Act to begin controlling greenhouse gas emissions and to implement a national cap-and-trade program.