(CBS News) NEW YORK - From afar, we watched this summer as four Vancouver-based men launched their custom-made, kevlar-coated, wood and fiberglass row boat, the Arctic Joule, from Canada's Northwest territory in early July, heading east, toward Greenland.
The rowers -- Kevin Vallely and Frank Wolf, from Canada, with Denis Barnett and Paul Gleeson, originally from Ireland -- set out to navigate part of the mythic Northwest Passage, the Arctic waters between Europe and Asia, a long-sought shortcut between the Pacific and Atlantic oceans.
For centuries, frozen ice made this sea route impassable. But the thinning Arctic sea ice, particularly during the summer melting season, has opened up the waters like never before.
"Warming of the climate system is unequivocal," stated the latest report from the Intergovernmental Panel on Climate Change, published Friday. "The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased."
The IPCC called the last three decades the warmest 30 year period of the last 1,400 years and found most of the gained heat has been stored in the oceans, spurring the melting of the polar ice caps. The panel forecast sea levels could rise three more feet by the end of this century.
Last year, summer Arctic ice covered the smallest area since satellite measurements began, according to the National Snow & Ice Data Center, in Colorado. This summer was the sixth smallest area.
Calling themselves the Mainstream Last First expedition, named after their sponsor, Mainstream Renewable Power, the rowers followed the route of Norwegian explorer Ronald Amundsen when he sailed the passage between 1903-06, the first documented successful voyage.
"Countless explorers have died in the Northwest Passage just because it's been chock full of ice over hundreds of years," said rower Kevin Vallely. "There's still ice up there, but there's far less ice than there was before, and we really wanted to bring awareness to that by traversing it solely under human power in a 25 foot row boat."
Their motto, painted on the boat, was "pulling together against climate change." The was no engine and no sails on board. Just two men at a time rowing, changing shifts every three hours.
"We did go for 50, 60, 70 hours at a time, and we got into the groove of doing that. You get a little sleep-deprived, but you do get your naps," Vallely said. "We needed to keep moving."
Their determined movements covered, on average, 21 miles a day. When the crew took a break to sleep, they typically dropped anchor at sea and snuggled in sleeping bags below deck in a tiny cabin most of us would find claustrophobic.
"At anchor, we could all four of us just squeeze in there kind of like sardines," rower Frank Wolf said. "Imagine like four dudes in boat about a month in having eaten just freeze dried food -- what that would have smelled like."
There were no baths, unless the rowers took a dip in the frigid waters.
Promoting alternative energy sources, three solar panels built into the boat powered their GPS and a desalinator that let them drink converted sea water.
Part of the mission was data collection for the Canadian Department of Oceans and Fisheries, so the rowers took measurements of the ice and water.
The rowers, ranging in age from 32 to 49, were all experienced adventurers. Vallely had trekked on skis across the South Pole in record time. Wolf has cycled the frozen Yukon to the northern coast of Alaska. Gleeson and Barnett had rowed the Atlantic.
But the Arctic adventure came with its own special danger.
"A piece of ice actually came in when we were sleeping at anchor and pinned our boat and was actually pulling us underneath the ice," Wolf said.
That ice was 40 feet thick. Vallely cut the boat's anchor so they could escape.
"The reality is this ice is supposed to be up at the pole. It's breaking up now," Vallely said.
Besides thinning ice, wildlife was another indicator of climate change.
They expected to see herds of musk-ox and caribou -- and did -- but it was a surprise to see grizzly bears roaming in polar bear country.
"They're seeing all these species up there that never used to be up there coming up from the South and now living in the Arctic," Wolf said.
In case the grizzlies set their sights on them, the rowers slept with a shotgun but never had to use it.
In the end, wind was their worst enemy, impeding their progress and sometimes making it impossible to row for entire days.
"It was the journey that mattered the most. We learned so much out there, and we tried everything we could," Vallely said. "Where we stopped we had to stop."
The rowers suspended their journey earlier this month after 55 days and 1,163 miles, reaching Victoria Island, about 700 miles short of their goal, but making it halfway to Greenland.
Wolf, an experienced environmental filmmaker, whose last release, "On The Line" discusses the controversial Keystone XL Pipeline project, documented the Arctic rowing trip and is planning to put together a feature film about it.
"Things are melting up there and changing up there. It's going to raise sea levels worldwide," Wolf said. "It's going to affect people in New York City; it's going to affect people in Los Angeles; it's going to affect people in any kind of coastal community."