Deirdre Shesgreen and Maureen Groppe

WASHINGTON – Missouri would have to significantly reduce its carbon emissions over the next 16 years under a proposal the Obama administration unveiled Monday to combat global warming.

The proposal could force Missouri's coal-fired power plants to dramatically change the way they operate — for example, by improving efficiency, switching to natural gas or even closing.

The draft environmental rule, a top domestic goal of the administration, is the centerpiece of President Barack Obama's climate change initiative. Power plants are the single largest source of greenhouse gas emissions in the U.S., generating about 38 percent of heat-trapping gases.

Under the proposal, Missouri would have to achieve a 21 percent reduction in carbon emissions per megawatt hour of electricity by 2030. Environmentalists in Missouri said the plan would improve the environment and public health, while business groups said it would hurt the economy.

No one disputed the outsized impact of the proposal on the Show-Me State.

Missouri's power plants produce more carbon dioxide than facilities in all but seven other states. That's because Missouri generates 83 percent of its energy from its 24 coal-fired plants.

EPA officials said Missouri's plants produced 1,963 pounds of carbon pollution per megawatt hour of electricity in 2012. The EPA wants that brought down to 1,544 pounds by 2030.

The EPA said it took into account each state's energy mix before setting state-specific goals.

"We don't have to choose between a healthy economy and a healthy environment," EPA Administrator Gina McCarthy said. "Our action will sharpen America's competitive edge, spur innovation and create jobs."

The Missouri Chamber of Commerce is part of a national coalition of business interests, the Partnership for a Better Energy Future, trying to stop the proposed regulations.

Also opposed is Sen. Roy Blunt, R-Mo. On Monday he said, "I will fight the president and his administration every step of the way to stop this unprecedented power grab and protect Missourians, who rely on coal for 80 percent of our state's energy."

A spokesman for the energy partnership, Chad Kolton, said: "The proposed emissions targets cannot realistically be met without forcing substantial closures of existing plants and taking major energy options off the table in the U.S. ... The resulting impacts on American jobs and the economy could be devastating."

Gov. Jay Nixon said in a statement that his administration would review the proposal "with a particular focus on making sure these proposed rules provide the flexibility Missouri needs to ensure consumers and businesses have access to reliable, affordable and sustainable energy from a diverse portfolio of sources now and in the future."

Environmental groups in Missouri and across the country cheered the proposal and said the benefits of reducing greenhouse gas emissions outweigh the costs.

"It'll be easier to meet the targets than to do nothing and deal with the droughts, severe weather, reduced food production and expensive disasters" that will result from climate change, said John Hickey, director of the Missouri chapter of the Sierra Club, an environmental advocacy group. "We need to take action if we're going to have a Midwest that our children can live in."

A federal advisory committee said in a report released last month that global warming is already damaging every region of the country and problems will increase. Effects in the Midwest include more intense heat waves, more humidity and worse air quality. More extreme rainfalls will cause erosion and affect water quality, according to the National Climate Assessment report.

The report said climate change will bring longer growing seasons that will increase the yields of some crops. But those benefits will be largely offset by extreme weather, causing agriculture production to decrease in the long term.

The EPA plan does not seek to mandate specific emissions levels for each power plant to meet; instead, the proposed rule would give states until June 2016 to decide how to cut pollution.

Besides adopting new technologies or increasing energy efficiencies, states could also buy emissions credits similar to the cap-and-trade system now being used by nine states in the Northeast and Middle Atlantic regions.

Supporters of national rules on power plant emissions argue that states like Missouri that have lagged other states in addressing greenhouse gases still have some of the easier steps at their disposal.

"Some states that have been overly reliant on coal will likely diversify to a wider range of cleaner energy resources and they'll have time to come up with a plan and do that," said Dan Bakal, director of electric power at Ceres, a sustainability advocacy group.

Missouri is among the 30 states that currently require utilities to generate a certain share of power from renewable sources. But that has not produced strong results so far.

Only 1 percent of the electricity generated in Missouri came from renewable sources in 2012, according to data from the EPA.

"We've got wind energy potential in Missouri. We've got solar energy potential in Missouri," said the Sierra Club's Hickey.

He also noted that Missouri ranks 43rd among states in energy efficiency, according to the American Council for an Energy Efficient Economy.

"So there's a lot of energy efficiency to capture," he said, "and that's one of the ways ... we can meet the new standards."

He and others argued that innovation in those two areas — renewable energy and energy efficiency — could create new jobs and spur economic development.

The Obama administration is taking executive action now because Congress killed a cap-and-trade bill in 2009. The White House is backed by a 2007 Supreme Court ruling that the EPA has the authority to regulate greenhouse gases under the Clean Air Act, as it does other pollutants, if it determines they're a threat to public health and welfare.

The EPA did that in 2009. Since then, it has limited carbon pollution from new vehicles by increasing fuel efficiency requirements. And it is in the process of finalizing emissions rules for future power plants. Those rules would essentially prevent the building of new coal-fired power plants unless they use carbon capture and storage, a technology still in its infancy.

The EPA is taking a more flexible approach for the nation's existing power plants. But the rules are still likely to be challenged in Congress and in court.

The EPA is expected to finalize the rules next June, after the EPA takes public comments and makes any revisions.

Even if the rules are enacted, critics say the emissions reductions will have little effect on global carbon pollution. Supporters say other countries — particularly China, the top emitter — are waiting to see what the United States does before taking action.

Polls show that Americans favor restricting carbon dioxide emissions from power plants, but dealing with global warming has not ranked high on the issues the public wants Washington to address.

What the EPA wants

Under the plan outlined Monday by the Environmental Protection Agency, Missouri and other states will be able to design their own plan to reduce emissions. Possible steps include:

• Improving the efficiency of existing power plants;

• Switching those plants from coal to natural gas;

• Increasing energy efficiency standards for commercial and residential buildings to reduce the demand for electricity;

• Investing in renewable energy sources, such as wind and solar.