Hill: Those who reject climate action have been increasingly reluctant to attack the underlying science, as overwhelming evidence points to the need to reduce manmade carbon pollution if we are to stop global warming. Instead, naysayers have adopted another line of argument: that the United States shouldn't take action because no one else is. A favorite punching bag has been China, which accounts for nearly 30 percent of global greenhouse gas emissions. Why should the United States reduce its carbon emissions,...