Nature: In his second inaugural address, President Obama announced a renewed commitment to addressing climate change, writes Jeff Tollefson for Nature. Despite efforts during his first term to reduce greenhouse gas emissions, much of the reduction was the result of the slow economy and the shift by power companies from burning coal to natural gas. One of the major ways Obama is expected to foment change is by imposing new regulations on power plants, which are responsible for about 40% of US emissions. In addition, three department heads key to the climate agenda—Steven Chu of the Department of Energy, Lisa Jackson of the Environmental Protection Agency, and Jane Lubchenco of the National Oceanic and Atmospheric Administration—are retiring, and Obama’s choices to replace them could further his climate agenda in the face of a still-divided Congress.