WASHINGTON — Taking aim at global warming, President Obama introduced a politically charged plan Monday to order big and lasting cuts in the pollution power plants discharge. But the plan, though ambitious in scope, wouldn’t be fully realized until long after Obama’s successor takes office and would generate only modest progress worldwide.
Obama’s proposal — to force a 30 percent cut in carbon dioxide emissions by the year 2030 from 2005 levels — drew immediate scorn from Republicans and industry groups, who called it a threat to the economy, and a few Democrats facing reelection campaigns in energy-dependent states. Environmentalists were split, with some hailing the plan and others calling it insufficient to prevent the worst effects of warming.
In all likelihood, the plan is one of the most significant steps Obama will take during his final years in office.
The effort would cost up to $8.8 billion annually in 2030, the Environmental Protection Agency projected. But the actual price is impossible to predict until states decide how to reach their targets, a process that will take years.
Obama, in a conference call with public health leaders, sought to head off critics who have argued the plan will kill jobs, drive up power bills, and crush the economy in some regions.
‘‘What we’ve seen every time is that these claims are debunked when you actually give workers and businesses the tools and the incentives they need to innovate,’’ the president said.
Never before has the United States sought to restrict carbon dioxide from existing power plants, although Obama’s administration is also pursuing the first limits on new plants. The plan would push the nation closer to achieving Obama’s pledge to reduce total US emissions by 17 percent by 2020, but still fall short of the global reductions scientists say are needed to stabilize the planet’s temperature.
Connie Hedegard, European Union commissioner for climate change, called the propoed rule ‘‘the strongest action ever taken by the US government to fight climate change.’’ But ‘‘All countries, including the United States, must do even more than what this reduction trajectory indicates.’’
Fossil-fueled US power plants account for 6 percent of global carbon dioxide emissions, so even a steep domestic cut affects just a portion worldwide. And coal plants that churn out carbon dioxide will still provide about 30 percent of US energy, according to predictions by the EPA, down from about 40 percent today.
Power plants are America’s largest source of greenhouse gases, accounting for 38 percent of annual emissions. Plants have reduced carbon emissions nearly 13 percent since 2005, meaning they are about halfway to meeting the administration’s goal.
The 645-page proposal forms the linchpin of Obama’s campaign to deal with climate change, and aims to give the United States leverage to prod other countries to act when climate negotiations resume in Paris next year.
At home, however, the limits won’t cut as big a chunk out of greenhouse gas emissions as Obama’s move to tackle pollution from cars and trucks. That separate effort is to double fuel economy for vehicles made in model years 2012-25.
And the timeline for the power plant plan, coupled with threats by opponents to block it, infused Monday’s announcement with uncertainty.
‘‘I know people are wondering: Can we cut pollution while keeping our energy affordable and reliable? We can, and we will,’’ said EPA administrator Gina McCarthy.
The EPA is giving customized targets to each state, then leaving it up to those states to develop plans to meet the targets. Some will be allowed to emit more and others less, leading to an overall, nationwide reduction of 30 percent.
Although Obama initially wanted each state to submit its plan by June 2016, the draft proposal shows states could get extensions until 2017. If they join with other states, as New York has done, they could have until 2018, kicking full implementation of the rules well into the next president’s administration.