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.