An Important Step on Global Warming On Friday, in a move that has already caused dismay in industry and among Congressional Republicans, the Obama administration proposed the first-ever federal limits on power plant emissions of carbon dioxide, which account for nearly 40 percent of the greenhouse gases America contributes to a gradually warming climate. The move, the first in a suite of executive actions on climate change promised by President Obama in June, is a welcome sign of his determination to move ahead on his own authority and bypass a Congress whose interest in tackling global warming is virtually nil. The proposed limits - which apply only to new power plants - will have no immediate effect on carbon emissions. But the long-term consequences for the way the nation produces energy will be significant. The rules would restrict emissions at new natural gas-fired plants to 1,000 pounds of carbon dioxide per megawatt-hour, and at new coal plants to 1,100 pounds per megawatt-hour. Because existing coal plants, even advanced ones, produce about 1,800 pounds per megawatt-hour, industry will find it virtually impossible to build new coal plants without capturing and storing some or all of their carbon emissions - a technology the administration has promised to promote but which has not been commercially demonstrated on a wide scale. New gas-fired plants should easily fit under the new limits because they now produce only about 800 to 850 pounds per megawatt-hour. The rules for new plants are far less costly and contentious than the rules the Environmental Protection Agency is now drawing up to regulate thousands of existing power plants, the ones producing all those emissions. Even so, the coal industry and its Congressional allies are already up in arms. In a typical comment, Mitch McConnell, the Senate Republican leader, described the rules for new plants as an "escalation" of the administration's "war on jobs" and a further manifestation of its "war on coal." This greatly oversimplifies matters. Coal's share in the national energy mix has been declining; coal provided more than half of electricity generation in 2003 but only 37 percent in 2012. New regulations governing emissions of mercury and other pollutants have accounted for part of this decline by forcing utilities to retire some older coal-fired plants. But coal's main enemy has been the marketplace - the discovery of abundant supplies of cheaper natural gas and the remarkable advances in wind and solar power that have encouraged power companies, for economic reasons alone, to switch to cleaner fuels. Our advice to Mr. Obama and his new E.P.A. administrator, Gina McCarthy, is to ignore industry's usual claim that the sky is falling and push ahead. For various reasons - the recession, the closing of some coal-fired plants, the tough new automobile mileage standards - the United States has made commendable progress in reducing its emissions, and is halfway toward meeting Mr. Obama's pledge at the Copenhagen climate summit meeting in 2009 to reduce its emissions by 17 percent from 2005 levels by 2020. But the news from the rest of the world - steadily increasing atmospheric concentrations of carbon dioxide, rising sea levels, more violent weather events, persistent droughts - is not encouraging. The burden on the United States to set a positive example is as heavy as ever.