The global energy picture has rarely been more dynamic than it is today. The United States in just a few years has become an energy superpower, as it begins to exploit enormous shale and deep water fossil fuel reserves. The price of silicon dropped 80 percent between 2008 and 2012. More than two dozen bankruptcies of wind and solar companies is expected to spur a tripling of investment in renewables by 2030. Scientists watch warily as extreme weather events become the new normal, even as global average temperatures seem temporarily plateaued at historic highs.