The U.N. Intergovernmental Panel on Climate Change's (IPCC's) latest report, which explores ways to cut carbon emissions, put the world on notice. Despite efforts in the United States, Europe and developing countries such as China to ramp up energy efficiency and renewable energy, global carbon emissions have been increasing at a much faster clip than they were just a few decades ago. To avoid the worst of the worst, IPCC scientists say emissions will have to be reduced 40 percent to 70 percent by 2050 and warn that we only have a 15-year window to reverse course.