Global warming has become perhaps the most complicated issue facing world leaders. On the one hand, 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. On the other, the technological, economic and political issues that have to be resolved before a concerted worldwide effort to reduce emissions can begin have gotten no simpler, 
particularly in the face of a global economic slowdown.
After years of preparation for climate talks taking place in Copenhagen through Dec. 18, 2009, President Obama and other leaders announced on Nov. 15 what had already become evident — that no formal treaty could be produced anytime soon. Instead, the leaders pledged to reach a placeholder accord that would call for reductions in emissions and increased aid to help developing nations adapt to a changing climate and get access to non-polluting energy options.
This would in theory give the nations more time to work out the all-important details. Negotiators would then seek a binding global agreement in 2010, complete with firm emission targets, enforcement mechanisms and specific dollar amounts to aid poorer nations.
At the heart of the debate is a momentous tussle between rich and poor countries over who steps up first and who pays most for changed energy menus.
Read More...
In the meantime, recent fluctuations in temperature, seized on by opponents of emissions restrictions, have intensified the public debate over how urgently to respond. The long-term warming trend over the last century has been well-established, and scientists immersed in studying the climate are projecting substantial disruption in water supplies, agriculture, ecosystems and coastal communities.
Scientists learned long ago that the earth's climate has powerfully shaped the history of the human species — biologically, culturally and geographically. But only in the last few decades has research revealed that humans can be a powerful influence on the climate as well.
A growing body of scientific evidence indicates that since 1950, the world's climate has been warming, primarily as a result of emissions from unfettered burning of fossil fuels and the razing of tropical forests. Such activity adds to the atmosphere's invisible blanket of carbon dioxide and other heat-trapping "greenhouse" gases. Recent research has shown that methane, which flows from landfills, livestock and oil and gas facilities, is a close second to carbon dioxide in impact on the atmosphere.
In the last several years, t
he scientific case that the rising human influence on climate could become disruptive has become particularly robust.
Some fluctuations in the Earth's temperature are inevitable regardless of human activity — because of decades-long ocean cycles, for example. But centuries of rising temperatures and seas lie ahead if the release of emissions from the burning of fossil fuels and deforestation continues unabated, according to the Intergovernmental Panel on Climate Change. The panel shared the 2007 Nobel Peace Prize with former Vice President Al Gore for alerting the world to warming's risks.
Despite the scientific consensus on these basic conclusions, enormously important details remain murky. That reality has been seized upon by some groups and scientists disputing the overall consensus and opposing changes in energy policies.
Steps Toward a Response
The debate over such climate questions pales next to the fight over what to do, or not do, in a world where fossil fuels still underpin both rich and emerging economies. With the completion of the United Nations Framework Convention on Climate Change at the Earth Summit in 1992, the world's nations pledged to avoid dangerously disrupting the climate through the buildup of greenhouse gases, but they never defined how much warming was too much.
The Group of 8 industrial powers also agreed this year to a goal of reducing global emissions 50 percent by 2050, with the richest countries leading the way by cutting their emissions 80 percent. But they did not set a baseline from which to measure that reduction, and so far firm interim targets — which many climate scientists say would be more meaningful — have not been defined.
At the same time, fast-growing emerging economic powerhouses, led by China and India, still oppose taking on mandatory obligations to curb their emissions. They say they will do what they can to rein in growth in emissions — as long as their economies do not suffer. The world's poorest countries, in the meantime, are seeking payments to help make them less vulnerable to the impacts of climate change, given that the buildup in climate-warming gases so far has come mainly from richer nations. Such aid has been promised since the 1992 treaty and a fund was set up under the Kyoto Protocol. But while tens of billions of dollars are said to be needed, only millions have flowed so far.
In many ways, the debate over global climate policy is a result of a global "climate divide.'' Emissions of carbon dioxide per person range from less than 2 tons per year in India, where 400 million people lack access to electricity, to more than 20 in the United States. The richest countries are also best able to use wealth and technology to insulate themselves from climate hazards, while the poorest, which have done the least to cause the problem, are the most exposed.
President Obama came into office vowing to take swift action on climate change, and under him, the Environmental Protection Agency has declared that it will regulate carbon dioxide emissions. But with the cap-and-trade bill facing an uncertain future in the Senate, his ability to take big steps on the issue has been severely constrained, and without significant actions by the United States, China and India had made it clear they would remain on the sidelines. Just weeks before the planned Copenhagen session, he and other leaders gathered for an Asian summit announced that no treaty would be reached in 2009. Instead, leaders will try to reach a political agreement that could be the basis for new treaty talks in 2010.
In the meantime, a recent dip in emissions caused by the global economic slowdown is almost certain to be followed by a rise, scientists warn, and with population and appetites for energy projected to rise through mid-century, they say the entwined challenges of climate and energy will only intensify.
