Here's How Obama Defends His Approval of Shell's Arctic Drilling

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President Obama has made addressing climate change a top priority. But environmentalists have criticized the president for pledging to curb domestic greenhouse gas emissions and pushing for an international climate agreement, on one hand, and promoting expanded fossil fuel production, particularly in the Arctic Ocean, on the other hand.

It's a contradiction that Obama was forced to explain during a Twitter question and answer session about climate change on Thursday.

Ready to answer your questions on climate change. Let's do this! — President Obama (@POTUS)May 28, 2015

In early May, the administration granted Royal Dutch Shell conditional approval to conduct exploratory drilling in the Chukchi Sea, which lies off the northwestern coast of Alaska. Approval came despite Shell's disastrous effort in 2012, when one of its ships, the Noble Discoverer, was plagued by mechanical problems, and its drilling rig, the Kuluk, ran aground in Alaska.

Shell aims to tap into the Arctic Ocean's vast store of fossil fuels, estimated to be nearly 90 billion barrels of oil and trillions of cubic feet of natural gas.

Conservationists are concerned that a spill in the remote and unpredictable Arctic Sea could prove catastrophic for wildlife. The nearest Coast Guard station equipped to handle spills lies a thousand miles away.

Related: Shell's kicking off its Arctic drilling effort, but kayaks and court orders stand in its way

A participant in Thursday's Twitter conversation, @BigBennyFL, asked President Obama to reconcile his concerns about climate change with his approval of Arctic drilling.

— Ben Alexander (@BigBennyFL)

May 28, 2015

The President provided a two part answer, saying he was unable to prevent oil exploration and had required Shell to meet higher standards than the company had originally proposed.

.— President Obama (@POTUS)May 28, 2015

.— President Obama (@POTUS)May 28, 2015

Opposition to Shell's Arctic drilling campaign — and Obama's stamp of approval — is on the rise as the oil company prepares to drill in the Chukchi Sea this summer.

Environmentalists have blockaded Shell's Arctic drilling ships in the Pacific Northwest and Seattle officials have sought to prevent the company's vessels from docking at the Port of Seattle.

Among those ships is the Noble Discoverer, which Shell leases. The ship failed a Coast Guard inspection in early May, when engineers found that the ship's bilges were dumping oily water overboard. That problem was among several that cost the ship's owner, Noble Drilling, $12.2 million in fines last year.

The déjà vu — so early in Shell's drilling operation — worries Travis Nichols of Greenpeace.

"Noble had problems with the oil water separator in 2012, which led them to plead guilty to environmental and maritime crimes — felonies," Nichols told VICE News in early May. "That doesn't bode well for the Arctic drilling program."

Related: Biloxis crude deal: Oil spill reparations are funding a baseball stadium in Mississippi