US President Barack Obama viewed Alaska's monumental Exit Glacier, in a bid to drive home the impact climate change is already having on America.

Obama traveled to southern Alaska's Kenai Fjords National Park, where he stood against the backdrop of the vast, but receding glacier, where posts mark the ice's retreat since 1815.

"This is as good of a signpost of what we're dealing with when it comes to climate change as just about anything," Obama said.

He pointed to a changing climate that has brought less snow and longer, hotter summers and an icy retreat has been anything but glacial.

"This place has lost about a mile and a half over the last couple hundred years. The reduction in glaciers has accelerated each and every year," Obama said.

Flora and fauna has been affected in the spectacular park, while melting glacier ice has raised sea levels.

"We want to make sure that our grandkids can see this," Obama said.

Obama is in Alaska to build support for domestic carbon reduction rules and a global pact to cap global temperature increases.

In December, representatives from around the world will gather in Paris to try to thrash out a deal to limit rises to two degrees Celsius (3.6 degrees Fahrenheit) over pre-industrial levels.

Obama had flown in to the base of the glacier over mountains partly covered in snow and turquoise waters.

"How's this? Beats being in the office," he said.

In an effort to take his message a broader audience, Obama on Tuesday got a "crash course in survival techniques" from insect-eating British adventurer Bear Grylls.

The footage will be used for an upcoming episode of "Running Wild With Bear Grylls."

Grylls, a former special air service trooper, boasts that he pushes celebrities like New Orleans Saints quarterback Drew Brees and Oscar-winning actress Kate Winslet "beyond their limits."

The White House has admitted that the Secret Service had vetoed some high octane suggestions from the producers.

Previous guests have been asked to eat mice, jumping out of planes and climb desert monoliths.

Challenge of the century

On Monday, Obama warned that climate change is no longer a problem of the future, but rather a challenge for now and one that will define the next century.

Describing the "urgent and growing" threat that he said was not being addressed quickly enough, he sketched the problems already facing people living in one of America's last wilderness frontiers.

The challenge "will define the contours of this century more dramatically than any other," Obama told a conference in Anchorage.

"Human activity is disrupting the climate, in many ways faster than we thought," he said, with one eye on Republicans who reject humans' role in heating the planet.