Trap natural gas.
Fracking is a nasty business. Among other problems, methane leaks from natural gas wells and pipelines. One recent study found leakage rates of up to 17 percent of production. For the climate, that's a big problem: As a greenhouse gas, methane is 25 times more potent than carbon dioxide. Solution: an EPA crackdown on fugitive methane emissions. Obama is a big natural-gas booster and a quiet supporter of fracking, so this is likely to happen, but he may avoid harder problems like drinking-water pollution or wastewater disposal.