For more than two decades, diplomats have struggled to slow global warming. They have negotiated two major treaties to achieve that goal, the 1992 UN Framework Convention on Climate Change and the 1997 Kyoto Protocol. And last year, at the UN Climate Change Conference in Durban, South Africa, they agreed to start talking about yet another treaty. A small group of countries, including Japan and the members of the European Union, now regulate their emissions in accord with the existing agreements. But most states, including the largest emitters of greenhouse gases, China and the United States, have failed to make much progress. As a result, total emissions of carbon dioxide, the leading long-term cause of global warming, have risen by more than 50 percent since the 1980s and are poised to rise by more than 30 percent in the next two to three decades.
The ever-increasing quantity of emissions could render moot the aim that has guided international climate diplomacy for nearly a decade: preventing the global temperature from rising by more than two degrees Celsius above its preindustrial level. In fact, in the absence of significant international action, the planet is now on track to warm by at least 2.5 degrees during the current century -- and maybe even more. The known effects of this continued warming are deeply troubling: rising sea levels, a thinning Arctic icecap, extreme weather events, ocean acidification, loss of natural habitats, and many others. Perhaps even more fearsome, however, are the effects whose odds and consequences are unknown, such as the danger that melting permafrost in the Arctic could release still more gases, leading to a vicious cycle of still more warming.
All these risks are rising sharply because the traditional approach to international climate diplomacy has failed. For too long, climate science and policymaking have focused almost exclusively on emissions of carbon dioxide, most of which come from burning fossil fuels. Weaning the planet off fossil fuels has proved difficult, partly because expensive and rapid shifts to new energy