The Republican takeover of the U.S. Senate, the result of Tuesday's election, may alter the nation's posture on energy and the environment. The power shift could put a climate change denier in charge of a key environment panel, pave the way for the Keystone XL pipeline, and lift a four-decade U.S. ban on crude oil exports.

Republicans won control of the Senate for the first time in eight years and expanded their majority in the U.S. House of Representatives. Emboldened, they will also likely move to block funding for the crown jewel of Obama's climate agenda: the Environmental Protection Agency's proposed rules to limit greenhouse gas emissions from power plants.

This looming political shift could slow U.S. efforts to reduce heat-trapping emissions and comes just days after scientists on the United Nations' Intergovernmental Panel on Climate Change urged swift action to slash emissions from the burning of fossil fuels.

Republicans can block Obama Administration regulations with a joint congressional resolution of disapproval that requires only a simple majority vote. Yet to advance their own bills, they're unlikely to muster the 60 votes needed to end Democrat-led filibusters in the Senate or the two-thirds majority needed to override an Obama veto.

"The gridlock will remain the same," says David Victor, a University of California, San Diego, professor who specializes in energy and environmental policy. "Gridlock in the center of government means it doesn't matter who's responsible for not getting things done."

Still, the GOP shift could reshape the energy debate in these four ways:

1. Stronger Resistance to Power Plant Rules

A clarion signal of change will occur in the Senate Committee on Environment and Public Works. The chairmanship is expected to shift from liberal California Democrat Barbara Boxer, a climate activist, to Oklahoma Republican James Inhofe, author of the 2012 book The Greatest Hoax: How the Global Warming Conspiracy Threatens Your Future.

Inhofe, who chaired the panel from 2003 until 2007, has called the scientific consensus that man-made carbon emissions are causing climate change the "greatest hoax ever perpetrated on the American people."

He joined a GOP effort earlier this year to block an EPA proposal that would limit emissions from new power plants. As committee chairman, his biggest target will likely be EPA's sweeping June proposal—known as the Clean Power Plan—to cut carbon pollution from existing power plants up to 30 percent by 2030, compared with 2005 levels.

He'll get help from reelected Senate Minority Leader Mitch McConnell of Kentucky, who's expected to take over as Senate leader. McConnell has indicated that he might use high-pressure tactics such as attaching amendments to must-pass spending bills that would block EPA funds for developing and enacting the rule.

Such budgetary tussles could put Obama, who has touted the EPA plan as a key U.S. climate effort, in a difficult position internationally, as countries gather next year in Paris to agree to new emission cuts.

View Images Sections of the Keystone XL pipeline's southern leg are lined up in Sumner, Texas. As Republicans take over the Senate, they may force a vote to approve the pipeline’s northern leg. Photograph by Tony Gutierrez, Associated Press

2. An Attempt to Force Obama's Hand on Keystone XL

McConnell also has indicated that he may use similar budget tactics to compel a vote to approve the pipeline, which could then require Obama to decide whether to use his veto power. The pipeline would carry heavy crude from Canada's Alberta region through Montana and South Dakota to the pipeline's southern leg, which begins in Steele City, Nebraska. (See: "Interactive: Mapping the Flow of Tar Sands Oil.")

The multibillion-dollar northern leg of the project, proposed by Calgary-based TransCanada six years ago, has been undergoing federal environmental reviews. (Related: "Can Senate Force Approval of Keystone Pipeline?")

Current Senate Majority Leader Harry Reid, a Democrat from Nevada, opposes Keystone XL and has stymied GOP efforts to force its approval. Many environmentalists also oppose the pipeline, saying it would spur the extraction and use of oil-sands crude, which is more energy intensive to produce than conventional oil.

Obama has said he would not approve the 1,179-mile pipeline if it increased emissions. The State Department's most recent review said it was not likely do so and argued that the oil sands would be developed whether or not Keystone was built.

3. A Move to Expand Fossil-Fuel Exports

A GOP-controlled Congress could push for speedier federal approval of projects that export liquefied natural gas. The Department of Energy has approved several so far, but Republicans have been nudging it to go faster.

Alaska Senator Lisa Murkowski, a Republican who's expected to become chairman of the Senate Committee on Energy and Natural Resources, favors lifting the crude oil export ban that was enacted in the early 1970s during the Arab oil embargo.

In September, Murkowski told reporters that next year could be the time to do that, citing research by the Government Accountability Office and other groups that suggest such exports could decrease gasoline prices. Environmentalists oppose lifting the ban, concerned that it could further spur U.S. oil production. (See: "Amid U.S. Oil Bounty, a Growing Debate Over Exports.")

"There's growing enthusiasm to revisit the crude oil export issue," says Scott Segal of the Washington, D.C., law firm Bracewell & Giuliani, which represents utilities as well as oil and gas companies. But he says whether lawmakers push to lift the ban could depend heavily on market forces, including oil prices. The recent price plummet has made oil production less lucrative and, in some areas, unprofitable.

4. Possible Passage of Energy Efficiency Bill

One measure that might pass Congress is a bipartisan bill to promote energy efficiency in residential, commercial, and federally owned buildings, co-sponsored by Senators Rob Portman, a Republican from Ohio, and newly reelected Jeanne Shaheen, a Democrat from New Hampshire. The bill didn't make it through the Senate this year, because it got tangled up in a larger vote on Keystone and other measures.

Once a Keystone decision is made, the bill may make it to the Senate floor, especially if both parties want to show they can pass legislation. Yet Goldston says he expects Republicans may try to block tougher efficiency standards for appliances, noting that they led the successful effort to defund the enforcement of rules requiring more efficient lightbulbs.

Aside from the Shaheen-Portman bill, not much new legislation is likely, says David Konisky, a Georgetown University professor focusing on energy and environment issues. "The discussions will change quite a bit," he says, adding the changes will be mostly rhetorical and symbolic.

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