Contrast those results with the failure of United Nations-led efforts to curb greenhouse gases chiefly by restricting the use of fossil fuels like coal, oil and natural gas. Earlier this month, top leaders in China and India — two countries that together produce about one-third of greenhouse gases — announced they would not be participating in the UN's one-day climate change summit in two weeks. There are still hopes that an international agreement to reduce emissions can be reached before the end of next year, but the choice to bypass the leadership summit does not bode well for future negotiations in Lima in December or Paris in 2015.