Nonetheless, many scientists are worried about rising emissions. The International Energy Agency estimated last month that coal will come close to surpassing oil as the world's top energy source in 2017 , when an additional 1.2 billion metric tons will be burned annually. In late November, the World Resources Institute reported there are nearly 1,200 proposed coal plants around the globe, three-quarters of which are planned for China and India.
By Jan. 1 of this year, the Kyoto Protocol was supposed to have cut the world's greenhouse gas output by 5 percent compared with 1990 levels. While the signatories as a whole are likely to meet that target, in part because of the shutdown of Eastern European factories during the 1990s, global carbon emissions overall rose 54 percent during that same period, according to the Global Carbon Project.
As a result, many experts are engaged in a discussion over whether they should continue pressing for ambitious carbon cuts in the near term or adjust their goals in the face of the prospect of a much warmer world.
In 2004, Princeton University professors Robert Socolow and Stephen Pacala wrote an influential paper outlining how the world could stabilize its greenhouse emissions by mid-century through a series of "wedges," using current technology, such as sharply increasing nuclear power worldwide, eliminating deforestation and converting conventional plowing to no-tillage farming.
Now, Socolow has published an article in the Vanderbilt Law Review that he describes as his "let's get real here" lecture, in which he outlines what the world can realistically achieve over the next four decades. Environmentalists "don't think it's time to start the bargaining" on what's an appropriate climate target, Socolow said, but they need to adjust some of their goals in light of the projected temperature rise.