It's been nearly 20 years since a handful of northeastern states got together to start a cap-and-trade program for their power sector's greenhouse gas emissions. Since then, the membership of the Regional Greenhouse Gas Initiative, or RGGI, has been anything but static. New Jersey left under former Republican Gov. Chris Christie, then rejoined under his successor. Virginia and Pennsylvania joined RGGI recently, but the current and likely future governors of those respective states are far from enthusiastic about it, signaling potentially more departures to come. However, RGGI has stood firm amid the swirling political winds and made meaningful reductions in emissions, according to William Shobe, an economist at the University of Virginia. Shobe spoke to Bloomberg Law's Jennifer Kay about why he thinks this markets-based approach to climate change has fared better than similar programs in other states—and in other countries. Do you have feedback on this episode of Parts Per Billion? Give us a call and leave a voicemail at 703-341-3690. See omnystudio.com/listener for privacy information.