The Obama administration's proposal for existing power plants to slash emissions by 30 percent by 2030 is being hailed by supporters as the centerpiece of the president's climate action plan.
But it's possible that President Obama's biggest climate move came in his first term, when he ushered in rules that would double the fuel economy of vehicles by 2025. The fuel-economy and greenhouse-gas-emissions standards for cars and light trucks finalized in 2012 could make a bigger dent in emissions than the power-plant rule, with more industry involvement.
Those vehicle rules, which require a fleetwide fuel-economy average of 54.5 miles per gallon by 2025, are projected by EPA to cut 580 million metric tons of greenhouse gases by 2030.
It's tough to make a direct comparison with the power-plant rules, but The Washington Post says those rules will cut 550 million metric tons by 2030 (according to EPA's rules, a state compliance model would mean a reduction of 555 million metric tons, while a regional compliance approach would mean 545).
Experts say the flexibility built into the power-plant rule makes an exact figure difficult to estimate before knowing how states will choose to meet EPA's 30 percent reduction goal.