Mongabay: The U.S. government aims to cut its greenhouse gas emissions 28 percent by 2020 under an order announced Friday by President Obama. “As the largest energy consumer in the United States, we have a responsibility to American citizens to reduce our energy use and become more efficient,” Obama said in a statement. “Our goal is to lower costs, reduce pollution, and shift federal energy expenses away from oil and toward local, clean energy.” The government is the largest single …