It’s a mystery.
President Obama called it the “most eloquent way” to reduce carbon emissions. The German environment minister thinks it’s the “the most tasty piece of the cake of transformative climate solutions.” French President François Hollande believesit is “an essential tool to…reduce greenhouse gas emissions.” The prime minister of Ethiopia said it could be an “opportunity for financing technology” to support climate action. But despite rapidly growing support from major nations, corporations and international organizations, an agreement on the need to price fossil fuels to address the fundamental drives of climate change is off the menu at COP21 climate conference in Paris.