Natural gas has also gotten cheaper, which is not purely positive for the climate, since it's a fossil fuel, but is mostly positive, since it emits much less carbon than coal. There are legitimate questions about methane and other fracking issues, but cheap gas is a big reason U.S. emissions have fallen 10% since 2004. In the past four years, one third of U.S. coal plants have been scheduled to close, and August set a new record for retirements. Globally, solar power has quadrupled since 2010. The cheaper solar gets, the more it is deployed, which further drives down prices, which further accelerates deployment.