The Shell Oil Company’s drilling rig Polar Pioneer in Port Angeles, Wash. on May 12. Environmental activists are preparing for three days of demonstrations starting on May 16 against Shell’s plans to store the Polar Pioneer and another rig in Seattle. (Reuters/Jason Redmond)

The United Nations’ top climate official took a subtle poke at the Obama administration on Wednesday over its decision to conditionally allow oil exploration off Alaska’s coast, suggesting that the Arctic’s oil and gas should stay underground.

Despite the tentative green light given to Shell Gulf of Mexico earlier this week, both the environment and Shell’s stockholders would be best served if such projects are shelved, said Christiana Figueres, the executive director of the U.N. Framework Convention on Climate Change.

“There is an increasing amount of analysis that points to the fact that we have to keep the great majority of fossil fuels underground,” Figueres said at a news conference.

[Obama administration grants Shell ‘conditional’ approval]

Figueres was responding to a question about the Interior Department’s decision on Monday to grant conditional approval to Shell’s plan to begin exploratory drilling later this year in the Chukchi Sea, off Alaska’s northeastern coast. The decision removed one of the last major hurdles for Shell’s Arctic plans, while also drawing sharp criticism from environmental groups who say drilling in such ecologically fragile  environments is too risky.

Figueres said she would not comment on the specifics of a U.S. policy decision. But generally speaking, she said, spending huge sums to extract fossil fuels from remote environments — what she termed “high-cost carbon investments” — is a risky proposition.

“One has to question the prudence of moving forward with those kinds of investments,” she said. “It is very evident that climate policy is advancing and progressing.”

The U.N. agency will facilitate this year’s international climate talks in Paris, where the world’s nations will attempt to negotiate reductions in greenhouse-gas pollution linked to climate change. So far, 37 countries representing 80 of the industrialized world already have submitted pledges to reduce carbon emissions, and dozens of developing countries are expected to do the same by October, Figueres said.

“All countries will contribute … in a transparent and measurable way,” she said.

Shell won federal leases for drilling in U.S. Arctic waters several years ago, but the company must till obtain federal and state permits before work can begin.

A growing number of climate scientists argue that much of the world’s remaining fossil-fuel reserves will have to remain in the ground to prevent global temperatures from rising by more than 2 degrees Celsius (3.6 degrees F) over historic averages, a figure cited by some experts as the maximum temperature increase the planet can tolerate without major disruptions to biological systems.

Shell officials dismiss such arguments as unrealistic. Ben van Beurden, the chief executive of Royal Dutch Shell, said in a 2014 Washington Post interview that oil and gas will still be needed for decades to come, even if solar and wind energy expand at dramatic rates.

“You can say, ‘Don’t worry it will all be supplied by renewable resources.’ Well that’s a fantasy,” van Beurden said. “I’m not against renewable resources. We’re very much invested in research and other ways of participating in it. But if you look at the most optimistic scenario, we think we are looking at still 75 percent of that energy demand by the middle of the century coming from fossil sources.”

Read more:

Shell executive says climate discussion has “gone into la-la land”

What the Shell mega deal says about the planet’s energy future

Sea levels are rising at faster clip as polar melt accelerates, new study shows

White House tightens oil-drilling rules as BP spill anniversary nears