Developing nations threatened to walk out of Copenhagen today, dramatizing the split between rich and poor that has haunted climate talks for 20 years. Who should move first to reduce greenhouse gases? Do developed nations, like the United States, owe something to those most threatened, like Tuvalu in the South Pacific? What about China, India and Brazil -- fighting poverty by industrializing now — in the process creating a new group of major polluters? We look at issues that could derail the best of intentions on dealing with Global Warming.