A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow increasing emissions of greenhouse gases. In an advance, however, the report's authors have used increasingly sophisticated models to evaluate how political and economic issues could affect various strategies to reduce emissions. It finds that growing opposition to biofuels and carbon capture strategies, for instance, could drive up costs of stabilizing atmospheric concentrations of carbon dioxide. But it also finds that these technologies could offer significant co-benefits, such as improved public health. It also finds that policies not specifically targeted at reducing emissions—such as air pollution and energy efficiency regulations—could help reduce emissions. The report is the last of three IPCC reports on climate science and policy.