Tackling a huge climate issue, the Obama administration Wednesday announced long-awaited measures to slash U.S. emissions of methane—a potent greenhouse gas—from the oil and gas industry. Setting an "ambitious" goal, the White House is aiming for a 40 to 45 percent cut from 2012 levels in the next ten years.

Releases of heat-trapping methane, the main component of natural gas, are rife in the booming oil and gas industry. Leaky equipment and the intentional flaring of "waste" gas at oil sites have been a side effect of the breakneck production that has made the U.S. the world's largest gas producer. The new target, according to the White House, will save enough natural gas in 2025 to heat more than two million homes for a year.

The U.S. proposal comes in advance of another round of United Nations-led climate talks later this year in Paris that aim to finalize a new global accord to slow global warming. Countries are expected, in the next few months, to announce their commitments.

The Natural Resources Defense Council called the plan "an important start," but NRDC and other environmental groups were critical of the focus on new oil and gas sites, rather than existing ones. "While addressing new sources is a critical step," said the group Earthjustice in a statement, "the Obama Administration must take stronger action to clean up existing sources."

The American Petroleum Institute called additional regulations "unnecessary." President Jack Gerard said, "Methane emissions have fallen thanks to industry leadership and investment in new technologies. And even with that knowledge, the White House has singled out oil and natural gas for regulation."

The methane rules, along with stricter vehicle efficiency standards and proposed limits on carbon dioxide emissions from power plants, are part of President Barack Obama's pledge to reduce overall U.S. emissions 17 percent from 2005 levels by 2020 and 26 percent to 28 percent by 2025. Some analysts have suggested that the U.S. can't get there without reining in methane, which accounted for nearly 10 percent of 2012 emissions. (See related story: "3 Obstacles Ahead for Surprise U.S.-China Climate Deal.")

The Environmental Protection Agency will issue a proposed rule this summer, the White House said, finalizing it in 2016. An announcement had been expected in December but was postponed.

Here are three key takeaways from Wednesday's announcement.

1. It approaches methane head-on ...

The plan calls for standards that directly address methane, rather than seeking cuts that are a by-product of reducing other pollution. In 2012, the EPA set restrictions on smog-forming volatile organic compounds at oil and gas sites, which by extension will reduce methane, the White House said. The earlier rule also targeted the methane emissions that occur when the drilling of a gas well is completed.

The 2015 rule will go further, focusing squarely on methane emissions at a broader range of sources, including oil wells, detailed in a set of white papers released last April. From the wellhead to processing facilities to the supply lines that carry natural gas to where it is used, eight million tons of methane were released into the air in 2014.

Footage from an infrared camera via the U.S. Environmental Protection Agency's Natural Gas STAR program shows methane escaping from a storage tank at a natural gas facility.

Climate advocates say that many of the fixes that could curb leaks from the oil and gas industry, which account for almost 30 percent of U.S. methane emissions, are simple and cost-effective. Indeed, many companies have taken action. Houston-based Southwestern Energy, for example, has led an industry effort to monitor for leaks and upgrade equipment. (See related story: "High Levels of Dangerous Chemicals Found in Air Near Oil and Gas Sites.")

The White House acknowledged that industry emissions are down 16 percent since 1990. "Nevertheless, emissions from the oil and gas sector are projected to rise more than 25 percent by 2025 without additional steps to lower them," it said. (See related story: "Oil and Gas Industry Faces Its Methane Problem.")

2. ... except at existing facilities.

The announcement refers specifically to methane standards at "new and modified oil and gas production sources." For the older facilities, the White House plan calls for the same "indirect" approach it took in 2012, setting standards for other pollutants that will incidentally reduce methane.

"Failing to immediately regulate existing oil and gas equipment nationwide misses 90 percent of the methane pollution from the industry," said Conrad Schneider, advocacy director for the Clean Air Task Force, an environmental group.

"We need to get reductions from existing sources. There's no question about that," said Dan Utech, White House special assistant on energy and climate change, in a press call following the announcement. Utech said the plan focused on newer sources because "that's where the investment is, that's where the increases in emissions are coming from."

The EPA will "continue to promote transparency and accountability" for existing sources by taking measures to ensure accurate reporting of emissions, the announcement said, acknowledging that reaching the target will depend on voluntary industry action through programs such as EPA's Natural Gas STAR.

"We are quite optimistic about the potential to work collaboratively with industry" on existing sources of emissions, Utech said. "That's the approach we're taking at this time."

The Clean Air Task Force sounded less optimistic. "Voluntary measures on existing sources are no substitute for sensible standards," Schneider said. "Falling oil and gas prices mean companies will have less incentive than ever to participate in a voluntary program."

It was not immediately clear how many facilities would be considered "existing" under the new rules. The U.S. has more than 500 gas processing facilities and an estimated 1.1 million active oil and gas wells. (See related story: "New U.S. Ozone Rules Likely to Be Felt Nationwide.")

3. Other agencies will need to do their part.

Driving down methane will require, in addition to EPA's pending rule, a separate regulatory process through the Bureau of Land Management, which oversees oil and gas leases on public lands, and by the Pipeline and Hazardous Materials Safety Administration. Those agencies will also introduce new standards this year, the White House said.

Both pieces are significant: Gas flaring on public land cost the government an estimated $50 million or more in federal royalties in 2013, and a report last July said that $192 million in natural gas was lost through pipeline faults. (See related story: "Oil Drillers' Burning of Natural Gas Costs U.S. Millions in Revenue.")

"We're not going to get there overnight. I don't think anybody thinks that's possible," Utech said of the 40 to 45 percent reduction target. "But we think that this set of steps puts us on a trajectory to hit that goal."

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