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President Barack Obama challenged fellow world leaders in unusually blunt language Monday to act boldly on climate change or "condemn our children to a world they will no longer have the capacity to repair."

In a forceful address, Obama opened the "GLACIER" conference in Anchorage, Alaska, by declaring: "We are not moving fast enough. None of the nations represented here are moving fast enough."

That includes the U.S., which Obama said "recognizes our role in creating this problem and embraces our role in solving it."

"It's not enough to just talk the talk. We've got to walk the walk."

Obama is using the three-day GLACIER conference — it stands for Global Leadership in the Arctic: Cooperation, Innovation, Engagement and Resilience — as a way both to highlight the perils of global warming and to cement his environmental legacy. He directly attacked politicians who argue that climate change isn't real, saying they "are on their own shrinking island."

"The time to heed the critics and the cynics and the deniers is past," the president said.

Unless the world acts more aggressively and more quickly, he said, "entire nations will find themselves under severe, severe problems: More drought. More floods. Rising sea levels. Greater migration. More refugees. More scarcity. More conflict."

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In language unusual for a diplomatic setting, Obama contended, "Any leader willing to take a gamble on a future like that, any leader who refuses to take this issue seriously or treats it like a joke, is not fit to lead."

"It's not enough to just have conferences," he said. "It's not enough to just talk the talk. We've got to walk the walk."

The setting was carefully chosen — opening the first visit by a sitting president to the Alaska Arctic on the day North America's tallest peak, Mount McKinley, was officially renamed to its original name, Mount Denali.

The high-profile three-day journey will include viewing melting glaciers and eroding coastlines and chats with salmon fishermen whose livelihoods are being affected — as well as an appearance on an episode of NBC's "Running Wild With Bear Grylls." The episode is set to air later this year.

The Obama administration has tried a variety of methods and used a number of venues to move the issue of climate change from the periphery to the fore.

Over the past several years, the president and members of his administration have woven the theme of climate change into speeches on troop readiness, health and the ecosystem of the Everglades. And those efforts have included making the case to address climate change by connecting the science behind global warming to a moral imperative for future generations.

The administration has also increasingly used a regulatory approach to address carbon pollution — setting the first national standards to cut carbon emissions from power plants. Internationally, the White House checked a huge box last year by securing an agreement with China to cut carbon emissions drastically by 2030 and a deal with Brazil to increase renewable energy production.

Related: Mt. McKinley to Denali: How a Mountain's Renaming Got Tied Up in Politics

However, the administration's efforts have also rankled environmentalists, as well as conservatives who argue that he has gone too far.

Just weeks ago, Obama gave final approval to Shell Oil's drilling in the Alaskan Arctic for the first time in 20 years — a move that raised the hackles of environmentalists, who accused his administration of hypocrisy.

And indeed, just moments after he finished speaking Monday, Greenpeace shot out a statement saying, "It's time for the president to stop talking about urgency, and stop approving extreme fossil fuel projects like Shell's Arctic drilling plans."

Meanwhile, amid concerns that the U.S. has ceded influence to Russia in strategic Arctic waters, the White House announced Tuesday that it would ask Congress to speed up construction of new icebreakers to protect U.S. interests and natural resources. The U.S. currently has two working icebreakers, compared to Russia's 40.