Adventurer Sir David Hempleman-Adams has called on politicians to "grasp the nettle" on climate change and stop paying "lip service" to their promises after witnessing the devastating impact of global warming during an expedition to the Arctic.
The explorer said his "worst fears" over disappearing sea ice were confirmed during a trip to circumnavigate the polar region by boat.
The journey around the Arctic via the Northeast and Northwest Passages traditionally takes three years, but his team managed it in just four months and a day.
Packed ice would have confounded sailors on the 13,500 nautical mile voyage in years gone by, but Sir David, a veteran of more than 30 Arctic expeditions who was knighted in the New Year Honours list, saw barely any for huge stretches at a time.
The 60-year-old, from Box in Wiltshire, fears irreversible damage to the Arctic landscape from climate change could open the route to potentially damaging commercial vessels.
And he believes disappearing ice and rising sea levels will have global environmental implications unless politicians act swiftly, telling the Press Association: "I think we're all a bunch of ostriches, and what we're doing is handing it to the next generation to sort out."
Comparing the loss of ice to the cutting down of the Brazilian rainforests, he said the Arctic had reached a "tipping point" which could lead to major flooding and famines.
He said: "We sort of pay lip service to the Paris climate accords trying to get carbon emissions down, but we just seem to be scratching the surface and we don't seem to be getting to grips with it.
"What are they going to do if the water rises so greatly and the conditions are such that we swamp London?"
Sir David and his crew set off on the Polar Ocean Challenge aboard the 48ft (14.6m) yacht Northabout from Bristol in June, aiming to circumnavigate the Arctic via Siberia, Alaska and Greenland in a single season to highlight the human impact on its fragile environment.
The expedition was a success - depressingly so.
After encountering little ice in the Laptev Sea north of Siberia, the yacht reached the Northwest Passage, where they found almost none for 1,800 miles (2,897km).
Sir David said: "We got around it in an incredible 14 days - it could take a couple of years in the past.
"We didn't see anything. The first ice we saw was in Lancaster Sound, at the very end of the Northwest Passage, on the last day of it.
"In years gone by we would have seen ice on the way and in some circumstances it would have stopped the trip."
Another section, the Bellot Strait, would normally be filled with small icebergs, but aerial footage taken by a drone revealed nothing but sea.
Sir David estimated that, with speedboats, they could have completed the entire circumnavigation in just a few weeks.
He said: "Whilst it was exciting, it proved my worst fears - that you could do both in one season. It's an absolutely depressing thought. I know it's a well-used adage, but the Arctic is the canary in the mine.
"What we're finding now is the ramifications of all this global warming, and it will definitely have an impact on us down in the South."
Sir David's fears for the Arctic are more than mere anecdotal observations.
Scientists reported air temperatures of 20C higher than normal for November with sea temperatures 4C above average, while sea ice coverage shrank to its second-ever lowest level this winter following record warmth.
Ice has declined by more than 30% over the last 25 years, with warnings the shrinkage could cause the disappearance of a third of the world's polar bears in the next 40 years.
While not a scientist himself, Sir David wanted the expedition to teach children and help people make up their own minds about climate change.
Polar Ocean teamed up with Wicked Weather Watch, a charity that teaches young people about climate change, blogging about daily life and sending photos and data back to thousands of schoolchildren around the world.
But while he may have inspired the next generation to protect the Arctic, Sir David believes action now is essential to limit the damage, saying: "The problem with politics is that you can change it overnight, but with the climate you can't."
He thinks new technology is vital to help high-polluting countries like China, Russia and the US become cleaner, but is adamant nothing will happen without strong political will.
Sir David said: "I don't think politicians and the general public have actually computed the correlation between climate change and a change in their life.
"If we said to everybody tomorrow - and people certainly get upset when a budget comes out and they put 2p on a packet of fags or pint of beer - 'You're going to take £1,000 out of your living allowance to pay for extra insurance' ... until you have a way of correlating an impact on individuals personally, so they can see immediately the effect of that, I don't think you'll get any change at all.
"Politicians are the same. They're a bunch of cowards and they don't want to lose their jobs. It's like turkeys voting for Christmas.
"A politician will not grasp the nettle until you have scientific evidence to say 'Climate change will do this, and when it does that you will get five million unemployed, you will get London under water, what are you going to do about it?'
"Until you've got concrete facts related to science where they can actually see the balance sheets, politicians aren't going to do anything."