"Don?t hold your breath, but future historians may look back on 2015 as the year that the renewable energy ascendancy began, the moment when the world started to move decisively away from its reliance on fossil fuels. Those fuels -- oil, natural gas, and coal -- will, of course, continue to dominate the energy landscape for years to come, adding billions of tons of heat-trapping carbon to the atmosphere. For the first time, however, it appears that a shift to renewable energy sources is gaining momentum. If sustained, it will have momentous implications for the world economy -- as profound as the shift from wood to coal or coal to oil in previous centuries..."