Countries have the potential to lower global greenhouse gas emissions before 2020 by a variety of means, according to a United Nations report released last week. Emissions reductions are needed before 2020 to boost the chances that the world can restrain human-caused global warming to 2 ºC above preindustrial levels by 2100—a policy goal that countries agreed to three years ago. The new report says nations have many opportunities to curb emissions during the next six years. For instance, the report says, improved energy efficiency has the potential to lower projected global greenhouse gas emissions by about 2 gigatons of carbon dioxide equivalent by 2020. Expanded use of renewable energy could prevent the release of between 1 and 2.5 gigatons of CO2 equivalent by 2020, and reform of fossil-fuel subsidies could eliminate between 1.5 and 2 gigatons of CO2 equivalent. Reducing emissions of fluorinated greenhouse gases—notably hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride—could curb about a half-gigaton of CO2 equivalent by 2020, the report adds.