In the late 16th century, the Dutch mariner Willem Barents spent three consecutive summers in the Arctic Ocean, scouting for a shortcut to the East Indies. The midnight sun, he figured, would surely blaze him a path. Yet he struck only ice beyond the 80th parallel. On top of that, the wildlife proved testy. On Barents’ first voyage, a polar bear ran amok aboard. On his next trip, another polar bear killed two of Barents’ men. And on the third, his crew had to spend a very long winter fighting off the creatures after their ship became ice-locked in the Kara Sea.

The fabled North East Passage may have eluded Barents but on his final attempt, in 1596, he discovered a fjord-riven landmass of “nothing more than mountains and pointed peaks”. It lay level with the north of Greenland and formed part of an archipelago three times the size of Wales. Barents called it Spitsbergen (literally “pointy mountains”). It was the most barren and forbidding land anyone had yet discovered, a glacial terra nullius where no one lived because no one could, and which for centuries would mark the edge of the known Earth.

Barents died on the return journey. The Dutch gave up their quest for a northern route, and continued to sail to their eastern colonies around Africa’s Cape of Good Hope. In time they stumbled upon other vast wastelands, but unlike the one they christened New Holland, Spitsbergen didn’t prove entirely a disappointment. The place teemed with what conservationists now call “charismatic megafauna”: whales, walruses, seals and polar bears, which the Dutch and, hot on their heels, the English keenly harpooned, clubbed and trapped for their tusks, blubber, baleen and fur. By the 1800s, when the Norwegians took over, there wasn’t a whole lot of wildlife left on or beneath the ice of Spitsbergen. Then the industrial revolution rolled around, and the ice itself was put on notice.

It’s a little easier these days to reach Spitsbergen, now known by its Norwegian name of Svalbard (“cold coast”). This past September, on the very day that the Arctic sea ice dipped to its annual summer minimum, a delegation arrived by air from Kiribati, a country even flatter than Barents’. Kiribati is a sprinkling of mostly coral atolls that, palm trees excepted, barely protrude from the Pacific. As well as straddling the equator, Kiribati skews the International Date Line, which makes it the only country that occupies all four hemispheres: north, south, east and west. You could almost call it a pole of sorts – certainly you’d be hard-pressed to find a more opposite place to Svalbard.

Kiribati’s president is Anote Tong, a keen fisherman and natural statesman who despairs for his country’s future in the face of rising sea levels. For years he has been warning fellow I-Kiribati that they must be prepared to evacuate, and his government has bought slabs of land in Fiji to help sustain them.

Tong was booked to address a climate-change summit of 120 world leaders in September in New York (Tony Abbott’s absence was noted), when Greenpeace invited him to detour via Norway. Tong and his entourage flew to Oslo, and from there 2000 kilometres north to Svalbard. One of the environmental organisation’s three ships, the Esperanza, lay waiting off Longyearbyen, the world’s northernmost and Svalbard’s only town, to take the Pacific Islanders still further north, deep into the fjord system. The I-Kiribati delegation, which also consisted of the president’s wife, his private secretary, his press attaché, an I-Kiribati climate activist and a security guard, would be on board for two days and one night.

In the weeks prior, the actor Emma Thompson and the fashion designer Vivienne Westwood had made similar forays aimed at drawing attention to Greenpeace’s Arctic campaign against the advance of oil exploration and industrial fishing. But hosting a head of state was new ground for Greenpeace. Kiribati’s population might be no more than that of Cairns but Tong had the ear of fellow leaders, including that of his friend Ban Ki-moon, the UN secretary-general. A group of prominent individuals was campaigning for Tong to be awarded the Nobel Peace Prize. After all, Kiribati was very much on the receiving end of what Barack Obama, addressing the New York summit a few days later, would call the “issue that will define the contours of this century more dramatically than any other” – more dramatically, Obama specified, than terrorism.

Tong speaks often of his crushing disappointment after the Copenhagen summit in 2009, when the world failed spectacularly to agree to anything that might help arrest global warming. Although he retains hope that a solution might be negotiated “one day”, he says it would likely come too late to save his nation. “The world is finally listening, but sometimes it all feels futile, you know. I have witnessed villages being inundated, but even at home people have trouble seeing the big picture. I would like to see the glaciers melting, not just for myself, but for all I-Kiribati people, so I can explain to them what I have seen, and why this matters, and what is happening to us, and why we must take action ourselves.”

Also, he hoped to see a polar bear.

Before embarking, we are taken on a snap tour of Longyearbyen by Jason Roberts, Greenpeace’s hired local “fixer” and a world authority on polar bears. Roberts arrived here 23 years ago, when the township serviced a small coalmine called Julenissegruva, or Santa Claus Mine. Today it resembles a mountain ski resort, albeit one at sea level, and with snowmobiles instead of skis. (The bears make skiing too dangerous, and cars are driven only in summer, when the roads reappear.) The town, population 2000, has become an unlikely travel hit and attracts upwards of 65,000 tourists a year, which is ten times as many as palm-fringed Kiribati gets.

“Norwegians come a lot, they love the outdoors and their polar history. They are not scared of the cold at all,” explains Roberts, adding that, thanks to their offshore oil and gas resources, Norwegians are also rich. Longyearbyen’s restaurants serve seal and reindeer, there’s a pub with 200 kinds of whisky, and every second business displays a stuffed polar bear.

At the popular new museum, Svalbard’s whaling history is celebrated as “the first oil adventure – a tale of courageous and adventuresome men and their dreams of wealth”. As if in anticipation of the “oil adventures” to come, another poster in the museum reads: “The Arctic is a robust region, not at all as vulnerable as once claimed.”

That’s not Greenpeace’s take on the subject. Aboard the Esperanza, a map of the world in the dining room shows the polar ice cap wrapping around Svalbard in winter. Historically, the ice cap would halve to a summer core of around 7.5 million square kilometres, an area the size of Australia. Since satellite imagery began recording the extent of ice cover in the late ’70s, however, the summer ice has been retreating, on average, by 13% per decade. In 2007, it shrank to 4.3 million square kilometres (which equates to Australia minus Queensland and the Northern Territory). In 2012, it was down to a record low of 3.6 million square kilometres (less New South Wales as well).

Although the summer ice cap has since rebounded a little, the North East Passage has become a reality for merchant ships. Since 2010, scores of bulk carriers have shipped iron ore, coal and other goods to China along the north coast of Siberia, a route about 25% shorter than the standard voyage – from, say, Rotterdam to Shanghai – via the Suez Canal. These are big, powerful ships, piloted by men with local knowledge and sometimes escorted by Russian nuclear-powered icebreakers – Willem Barents would doubtless still struggle to punch his wooden boat through the remaining bergs and floes. But the big melt is gaining pace. Scientists from the Norway-based Arctic Monitoring and Assessment Programme predict the summer Arctic will essentially be ice-free within two to three decades. By 2040, the North East Passage could be completed in a kayak.

Vladimir Putin’s enthusiasm notwithstanding, the global ramifications are serious. The Arctic helps to cool the Earth by giving off more heat to space than it absorbs. Remove the ice and snow cover, and the Arctic Ocean will absorb sunlight rather than reflect it, which helps explain why average Arctic temperatures have risen twice as sharply as those anywhere else. In Longyearbyen, the average winter temperature has risen by almost 3 degrees Celsius in the past 25 years, and Norwegian meteorologists predict it will rise another 10 by 2100.

Until now, average global sea-level rises have been modest, to the tune of 3 millimetres a year, mostly caused by a warming (and thus expanding) ocean and melting glaciers. But a recent study of sea-level changes during the past five ice-age cycles (over a period of 500,000 years) in the journal Nature Communications shows that once melting of the ice sheets has been triggered, it accelerates for many centuries. On current projections, seas will be up to a metre higher by 2100. Beyond then, there’s enough ice on Greenland alone to contribute another 5 or 6 metres.

There are better-case scenarios, should the world manage to drastically rein in its carbon emissions. But further amplification is looking much likelier: the warming of the Arctic has the big end of town excited precisely because it is putting virgin fossil-fuel fields within reach. The US Geological Survey has estimated that offshore oil and gas reserves within the Arctic Circle “account for about 22% of the undiscovered, technically recoverable resources in the world”, and companies like ExxonMobil, Norway’s Statoil, Shell, BP and various Russian outfits are all racing for a slice.

Leading the pack, so far, is the Kremlin-owned company Gazprom, which operates the Arctic’s first ice-resistant oil-drilling platform, about 1000 kilometres south-east of Svalbard. On 18 September 2013, activists from the Greenpeace ship Arctic Sunrise attempted to suspend a protest banner from the platform. The next day, the Russian Coast Guard seized the ship and jailed its 30 crew members and activists. The Arctic 30, as they became known, were set free after two months of international pressure, but President Putin had made his point. Three months later, in 24-hour darkness, the Prirazlomnaya platform began pumping the Arctic’s first offshore crude oil from beneath the sea ice.

Aboard the Esperanza, there are again 30 crew and activists, from 20 nations. The president of Kiribati and his entourage are met by the captain, who lends the Tongs his cabin, and Dima Litvinov, a Greenpeace veteran who was the first of the Arctic 30 to be released. Litvinov, whose loquacity is a point of merry affection within the organisation, has been getting himself arrested in the Arctic – and talking himself free – since 1990, when he protested against Russian nuclear-waste dumping in the Kara Sea. Keen to dispense with formalities, he engages Tong with talk of fishing, sailing, snorkelling and coconuts.

“I love the sea,” enthuses Litvinov, who grew up in a Siberian village, where his dissident father had been exiled under Leonid Brezhnev’s rule.

“I do, too,” says Tong. “But I must still learn to love this one.”

He glances out the dining-room window at the sullen fjord and the jagged peaks streaked white with ice. His press attaché smiles. The only signs of greenery are the scraggly pot plants on the sill.

Also aboard is David Ritter, the head of Greenpeace Australia Pacific. Ritter, a former native-title lawyer whose chipper intellectualism confounds the rugged Greenpeace stereotype, informs me that the trip has two “critical missions”: to film an interview with Tong on the ice ahead of the climate-change talks in New York, and to have Tong become the first head of state to sign Greenpeace’s International Declaration on the Future of the Arctic, in support of the organisation’s campaign to turn the Arctic Ocean into a global sanctuary. Litvinov’s charm offensive may or may not help.

A few hours later, ahead of an evening visit to a glacier, Litvinov hands the president his blue “teddy suit”, a plush onesie so comfortable that, as a Swedish crew member puts it, “Why would you ever take it off?” The same can’t be said for the next layer, which is orange. The hefty Arctic-class survival suits take some getting into, let alone getting used to. We blunder about like fat robots on the icy back deck, waiting for the seas to calm so that the inflatable boats can be manoeuvred alongside. The president’s wife has opted to stay indoors. “She feels very far from home,” explains Tong.

The crew are understandably nervous about having a visiting presidential party descend a rope ladder in rough weather. The last one into the dinghy is Jason Roberts, our designated driver. As we peel away from the Esperanza, he lurches over the side and heaves violently. “I like to feed the krill,” he says laconically, upon resuming the wheel. Later he tells me he once was seasick every day of a 65-day boat trip.

As well as a guide we have a guard: Longyearbyen’s resident policeman, who carries a rifle in the event of marauding polar bears. On Svalbard, it is illegal to venture outside town unarmed, for there are as many bears living here as humans.

Roberts speeds the dinghy into the gloom, towards a distant glacier. The waves are the colour of steel, the sky a shade lighter. Pretty soon, the Esperanza is a blot on the horizon, and icebergs begin to bob around us. A few are black with moraine (the grit picked up by a glacier), and we mistake them for animals. Others are as big as buses, and can be heard cracking. The policeman maintains a sharp lookout for swimming bears. The intention is to make landfall but it’s late as well as extremely cold and, assessing what may or may not be fear on the I-Kiribati faces, Roberts decides to turn around. “I always love a little adventure but this is different,” says Tong, back on the Esperanza. “The landscape is intimidating. I was not afraid but it was a bit strange to get into that gear and not be able to move. I felt like an astronaut.”

The Greenpeace strategists do well to hide their disappointment.

I wake up at 4 am to find that we are anchored off a grim Russian coal-mining settlement, Pyramiden, at the base of a mountain no more or less pyramid-shaped than the next. Around the fjord, all the mountains are weathered so evenly that their gullies look like pleats, with the fallen scree forming a steep, unbroken beach of moraine. Nature might be severe here, but it has never looked so tidy.

Although Pyramiden was abandoned 16 years ago, Russia, which is entitled to mine on Svalbard as part of a 94-year-old treaty with Norway, continues to operate another company outpost nearby. The Barentsburg mine is deeply uneconomical, but its raison d’etre is geopolitical: the Russians export a shipload of coal each year for the sake of maintaining their historical claim to the region’s resources. (Bizarrely, Australia is also a claimant under the Svalbard Treaty, as are 37 other countries, including Afghanistan, Venezuela and Monaco.)

Also up early is Pelenise Alofa, who heads up the Kiribati Climate Action Network. She’s been on the Esperanza before, in 2009, when it was used to blockade a coal-export terminal in central Queensland. A few months later, at the conclusion of the Copenhagen summit, she attended a dinner hosted by Tong. “He didn’t eat,” she recalls. “He was too upset. To see your own president in tears, for me, well, I was really affected by that. Copenhagen was a disaster, but for me it was the beginning.”

Alofa explains that Kiribati is made up of 32 low-lying atolls and one larger, elevated island, Banaba (formerly Ocean Island), which was hollowed by 80 years of phosphate mining. “I’m Banaban,” says Alofa. “Most Banabans were put on a ship and relocated to Fiji after the Second World War. So I know the pain of moving a people.”

Education and employment opportunities have further scattered I-Kiribati to surrounding nations. Alofa herself has lived and worked in Papua New Guinea, Fiji, Nauru and Sydney. But for most I-Kiribati the world remains a tiny place. Half of them live on South Tarawa, a necklace of atolls less than half a kilometre wide and linked by causeways. Alofa says rising seas are already infecting freshwater supplies and exacerbating sanitation problems. “Sooner or later we’ll have to move. Otherwise one big wave will do it for us.”

We duck out briefly into the cold to find David Ritter on deck clutching a cup of tea and contemplating a vast blue-lustred glacier at the end of the fjord. His head is wrapped in a college scarf (from the London School of Economics, where Tong also studied), but he looks pleased: overnight the president has agreed to sign Greenpeace’s Arctic declaration. “It’s not quite bringing down the fossil-fuel apparatus in one go,” says Ritter. “But it’s a step.” The plan is for Greenpeace’s media team to film Tong signing the declaration on the ice, or at least at the edge of the blue glacier. A moot point is how Tong is going to hold a pen – it’s not easy freeing up a hand in these conditions.

“What I really admire about him is that he takes action while in office,” says Ritter. “He’s not one of these leaders who waits till he’s out of office to correct his legacy.” The declaration’s signatories include quite a few of those.

Over breakfast a few hours later, Tong, who is 62, notes wryly that he’s used to being isolated. At just six he was dispatched from Kiribati’s outer Line Islands to a Catholic boarding school on the island of Abaiang, a four-hour flight west. He didn’t see his Chinese father again for six years. His mother visited once a year, via a copra cargo ship. “In boarding school you survive or you become a victim,” he says. “I never became a victim.”

He completed secondary school in New Zealand, followed by a science degree, before returning to what were then called the Gilbert Islands in 1974. In the lead-up to independence in 1979, Tong worked for the British colonial administration. Nine years later he completed his economics degree in London. He was elected Kiribati’s president in 2003. (His long-time rival for the presidency is his older brother, a doctor. The two no longer talk.)

“When I came to office, the writing of climate change was on the wall, but the science wasn’t yet so conclusive.” Also, says Tong, I-Kiribati people are deeply religious (Tong’s own party is called “Pillars of Truth”) and so endemically sceptical.

“What kept me going was thinking of the kids” – he has seven – “and the generations to come. Even if we can protect one of the islands with seawalls and the like, we don’t have the resources to save all of them. That’s why I’m advocating ‘migration with dignity’. What other choice do we have? I’ve read the reports. I’ve seen the science. It’s not science that’s the problem. It’s the economic models. The pursuit of profit at any cost is what got us into this mess.

“You take this place. When I look around I see beauty. At the same time, there is this feeling of sheer arrogance to the landscape. It demands respect. There is no chance of being at one with nature here. Nature is dominant. So why fiddle with it?”

By mid-morning we are back in our bulky orange suits, waiting for Jason Roberts and his rifleman to return from the Nordenskiöldbreen glacier in one of the inflatables. The two men and several of the Greenpeace crew have been out for well over an hour, scouting for a suitable place to make landfall, free of bears. Strong winds have chopped up the water, and there’s the added risk of large waves caused by the glacier “calving” slabs of ice. Yet when Roberts finally returns, there is little trepidation this time, only impatience to get out there.

The mouth of the glacier is 4 kilometres wide. Roberts tells me it has receded almost a kilometre in the two decades he has been coming here. We clamber stiffly ashore at its rocky northern edge, bracing ourselves against the wind.

The PR team selects a spot for the interview and Tong is handed a blue coat, previously donned by Roberts’ friend David Attenborough, to pull over his high-vis orange. He has barely sat down before he calls out. He is looking up at a ridge high to his right, across a small ravine, about 80 metres away. Peering right back at us is a polar bear. It hasn’t shown all of itself, just its head, tilted slightly upwards, as if judging us. The policeman scampers up some rocks to stand sentry, rifle at the ready, but the bear is untroubled. It moseys forward a pace or two, then squats and lays its big woolly head on its front paws, regarding us like a dog might. “It must have smelt us coming,” says Roberts.

Tong, a spiritual man, prefers to think of it as a welcoming. “I feel deeply honoured,” he says.

After ten minutes, the bear disappears behind the ridge. Our guard is on edge. The bear could readily skirt the ravine from behind. There are 14 of us ashore, and in our slow-mo suits we’d take an age to exit the headland. We’re ordered to get back on the inflatables, which are idling offshore, but one of the dinghy drivers shouts that she can see the bear from where she is. It is ambling away, and we’re allowed to stay.

The president signs the declaration with the slowly melting Nordenskiöldbreen behind him. A few Arctic terns swirl about ahead of their annual migration south. In just a month’s time, the sun will set and not rise again till late February. Suddenly the wind picks up, dark clouds swirl in, and we make for the boats. The ride back to the Esperanza is very rough; wave after icy wave splats over our hunched forms. Finally we bump alongside the Esperanza, and Litvinov is there to help the blue-lipped I-Kiribati up the ladder, one by one. At first he’s gleeful he didn’t join us. Then he kicks himself. In 25 years of Nordic activism, he has never seen a polar bear.

We spend the rest of the afternoon steaming back to Longyearbyen, past the striated mountains and the occasional sealer’s shack at their base. Ships in these waters must carry pilots with local knowledge, and ours is Torry Sakkariassen from Tromsø, on Norway’s north coast. He tells me he used to pilot wildlife tours to the sea-ice front, before it retreated too far. Sakkariassen also notes that the fjords have ceased to ice over in recent winters. “Once you could get here [from mainland Norway] four months of the year. Now you can get here 12 months a year, which is not good for the wildlife.”

He says northern Norwegians don’t mind the warmer summers, but the problem is that southern Norway’s foul winters have been creeping north as well: “We like our winters cold and dry, with lots of snow, not wet and miserable like in Oslo.”

Shortly everyone crams into the bridge for a glimpse of a pod of blue whales spouting water ahead. A few of us settle for a vantage spot outside. The sun has been hanging low all day, but on the lee side of the bridge, out of the prevailing westerly, the added reflection off the water gives it a tiny bit of kick.

Jason Roberts, the polar guide to the stars who prefers to stay in London when not seasick or skiing in the Alps or living in Longyearbyen, turns out to be Australian. He grew up shooting rabbits and foxes in Victoria’s Western District, attended (and survived) boarding school, became a Melbourne stockbroker and went looking for adventure. He was aiming for Africa when one sliding door in Norway led to another and he ended up working as a carpenter for a snow-fox trapper on Svalbard, via Lapland. It was 1991. Roberts explored the area and helped out on science projects. “I quickly realised filming in polar regions is more about logistics than about actual filming,” he tells me. “So I specialised in that.” Today he owns a studio, an engineering workshop and three sheds of Arctic gear – snowmobiles, cranes, tents, boats – on Longyearbyen’s harbourfront. He also has a polar base in the Falkland Islands, for Antarctic expeditions, and another in northern Canada. His many film and documentary credits include the Bond film Die Another Day and David Attenborough’s superb Frozen Planet series.

In the process, he has become one of the foremost field experts on polar bears, as well as on other wildlife, like Svalbard’s unique reindeer. (“These have very short legs; they look like pigs with antlers.”) Roberts says the changing climate is not all bad news for the local fauna. “You do have your winners as well, not just your losers. Barnacle geese, which nest here in summer, are one of the winners. Reindeer numbers are increasing. Less sea ice and warmer water may mean more food for walrus, we don’t know. But bears lose, as pack ice is their hunting platform.”

At the same time, he does not buy the poster image of the doomed polar bear, drifting forlornly on a fast-melting floe. “Polar bears are very adaptive. They will most likely survive but these changes will affect their home ranges. If bears get isolated on Svalbard [without access to sea ice], their populations would reduce dramatically. The bear that we saw has adapted to hunting in the local fjord system. I find it amazing it can find enough to eat. You see a 500-kilogram polar bear eating an Arctic tern egg, which is the size of your thumb, and you think, Was that really worth the effort? But they are amazing. They don’t hibernate, but they can sit out the season on those rocks until ice forms in the bay and they can hunt their main food again, which is seals.”

Roberts has come very close to being bear food himself once or twice, and owns the claw-torn hat to prove it. “You have to have total respect for them. They are very dangerous. For the record, if I do ever get killed by one, please don’t shoot the bear afterwards.”

The Esperanza rounds a final pointy mountain to bring Longyearbyen into view. My initial impression was of an ugly, alien town. But Roberts convinces me it is a town like any other, only naked. Missing are the trees and greenery used to camouflage human impact. Its heated sewerage pipes are elevated to avoid the permafrost. A prominent coal-fired power plant belches steam nearby.

Still, there’s something about Longyearbyen, in the way the place lets it all hang out as its surroundings warm and melt, that puts into bleak perspective the likelihood of the world ever agreeing to cut carbon emissions meaningfully – China and the United States’s recent deal notwithstanding. Perhaps it is simply as Roberts put it: climate change means there will be winners as well as losers. Russia and Norway will be winners, in the short to medium term at least. Kiribati and its Pacific neighbours, including Australia, will be among the losers. What makes someone like Anote Tong stand out among leaders is that he is brave enough to accept defeat.

“You can’t escape the immensity of what we have seen here, in the Arctic,” Tong tells me. “It leaves you with a sense of foreboding, that what has been set in train here can’t be stopped.”

Minutes later, though, in a farewell speech in the dining room, he congratulates the captain and his crew for trying.

“Sometimes I ask, ‘Why are you people doing this?’ But then I ask myself the same question. And the answer is that we are in this together.

“Our encounter with the polar bear was very symbolic. In our superstitious way, we I-Kiribati people think these are the people from the other land, the old land, who have come to welcome us. We think maybe he was looking after us, keeping us safe.

“We also think he would like us to return the favour, to keep him safe. Superstition or not, I feel that obligation. If we look after the world, the world will look after us. That is the message I will be taking to New York.”

It’s the sort of sentiment the crew knows to clap warmly. As a farewell gift, the captain presents Tong with the ship’s Greenpeace rainbow flag. Tong promises to hang it in a prominent place at home. He looks at his wife, who smiles back wanly, still feeling the cold.

“My wife is from Fiji,” he says. “Thirty-nine years ago, I asked her if she would come with me to Kiribati, and she said, ‘I will come with you to the end of the world.’”

He grins and looks around the room.

“Now, I have taken her there.”

Up above, the I-Kiribati flag, which honours the sun and the sea, convulses in the Arctic breeze, its edges already unravelling.

John van Tiggelen's visit to the Arctic was facilitated by Greenpeace