If this ever comes to war, blame it on a hat. In 1983, Canadian historian Kenn Harper had a chance encounter with an oil company scientist near Resolute, in the Canadian Arctic. The oilman was wearing a hat with the words 'Hans Island, Northwest Territories', in bold letters. Mr Harper is one of the very few people in the world who had ever heard of Hans Island, a tiny, uninhabited rock off the coast of Greenland where only polar bears and a few brave hunters roam. He found it curious that a Canadian oilman would be poking around this far north, so he wrote about it for a newspaper in Thule, Greenland. The story may have ended there. Thule papers are not widely read. But this one found its way to Copenhagen, the capital of Denmark, the country that owns Greenland, and which had long claimed sovereignty over Hans Island. Legend has it a Danish government official, Tom Hoyem, read the article, muttered angrily and promptly rented a helicopter. He flew to the island, planted a Danish flag and left a bottle of cognac next to it. It was the modern equivalent of a Viking raid. Hans Island is effectively worthless - no one lives there, nothing grows on it, it has no strategic value - but in modern diplomacy, flag-planting is serious business. Canada and Denmark had been quietly discussing Hans Island for years, but after the Hoyem incident and the publicity that followed it, it became a matter of national pride. Who were these upstart Danes anyway? The squabble festered, unresolved, until last year, when critics assailed the Canadian government for not doing enough to protect national interests in the far north. Somebody brought up Hans Island as an example of foreign encroachment. Piqued, a Canadian cabinet minister decided to fly to the island (without telling the Danes) and walk around it, like an animal demarcating its territory. Someone had already planted a Canadian flag, built a cairn and deposited a bottle of Canadian whisky, in case there were any doubts who was in charge. The Danish, furious, called it 'an occupation' and diplomatic notes flew. An official said the Danish had a historic claim because Greenlanders had always used the island 'as a lookout during polar bear hunts'. Polar bear hunts are illegal, retorted the Canadians. 'No Laughing Matter,' pronounced Canada's biggest paper, the Toronto Star. It said the minister's visit was 'crucial for asserting Canada's sovereignty over our vast far north'. Now peace could come as a result of global warming. If the polar ice caps keep melting, the ocean level may rise enough to swamp Hans Island altogether, and there would be nothing left to fight about.