Global warming

Global warming has become perhaps the most complicated issue facing world leaders. Warnings from the scientific community are becoming louder, as an increasing body of science points to rising dangers from the ongoing buildup of human-related greenhouse gases — produced mainly by the burning of fossil fuels and forests.

Global emissions of carbon dioxide were at a record high in 2011 and were likely to take a similar jump in 2012, scientists reported in early December 2012 — the latest indication that efforts to limit such emissions are failing.

Over all, global emissions jumped 3 percent in 2011 and are expected to jump another 2.6 percent in 2012, researchers reported.

The new figures show that emissions are falling, slowly, in some of the most advanced countries, including the United States. That apparently reflects a combination of economic weakness, the transfer of some manufacturing to developing countries and conscious efforts to limit emissions, like the renewable power targets that many American states have set. The boom in the natural gas supply from hydraulic fracturing is also a factor, since natural gas is supplanting coal at many power stations, leading to lower emissions.

But the decline of emissions in the developed countries is more than matched by continued growth in developing countries like China and India, the new figures show. Coal, the dirtiest and most carbon-intensive fossil fuel, is growing fastest, with coal-related emissions leaping more than 5 percent in 2011, compared with the previous year.

Emissions continue to grow so rapidly that an international goal of limiting the ultimate warming of the planet to 3.6 degrees, established three years ago, is on the verge of becoming unattainable, said researchers affiliated with the Global Carbon Project, a network of scientists that tracks emissions.

Yet nations around the world, despite a formal treaty pledging to limit warming — and 20 years of negotiations aimed at putting it into effect — have shown little appetite for the kinds of controls required to accomplish that goal.

For almost two decades, the United Nations has sponsored annual global talks, the United Nations Framework Convention on Climate Change, an international treaty signed nearly 200 countries to cooperatively discuss global climate change and its impact. The conferences operate on the principle of consensus, meaning that any of the participating nations can hold up an agreement.

The conflicts and controversies discussed are monotonously familiar: the differing obligations of industrialized and developing nations, the question of who will pay to help poor nations adapt, the urgency of protecting tropical forests and the need to rapidly develop and deploy clean energy technology