Inside the Arctic Circle in Abisko: It has been a race against time to bring in the reindeer from their mountain summer grazing ground, but today Per-Martin Kuhmunen, a 39-year-old traditional Sami herder is triumphant.

“We brought them in today,” he says with a grin, as he and two other members of the Gabna herding district sit exhausted, bruised and battered, in a cabin on the outskirts of the village of Abisko in the far-northern corner of Swedish Lapland.

The herders, like those from other districts in Sweden, have been forced to bring their 6,500 reindeer in from mountain pastures a month early after unusually early and heavy snowfall linked to climate change meant their animals could not find food.

“The problem comes when the ground is still warm,” says Tomas Svonni, the district’s chairman. “When you get snow on warm ground, you get ice at the bottom, and the food which the reindeer eat becomes frozen.”

Inside the cabin, there’s a fug of sweat, wet clothes and boiled reindeer meat. Parked outside are the snowmobiles, dayglo lassos hanging from the handlebars, on which the men have spent four days ranging over the slopes in search of their animals.

Christer Johansson is busy sawing and screwing planks in darkness, even though it’s only early afternoon. He is racing to finish the wooden pens where the deer will be separated by owner. “There’s a little bit of a panic to get the reindeer down,” he says. “They can’t find any food up on the mountain, so they have to come down to the forest.”

This Arctic corner of Sweden is seeing some of the most dramatic changes to weather patterns on earth.

According to the Swedish Meteorological and Hydrological Institute, temperatures here were on average more than 3C higher between 1991 and 2017 than between 1961 and 1990. That is more than six times the 0.5C increase estimated for the world as a whole.

“The biggest thing is the temperature differences: it can be pretty warm one day and -30C the next day,” Svonni explains. “We haven’t seen this before. This is new for us.”

Warmer air in the Arctic makes the weather more changeable. This can push cold Arctic air down over northern Sweden, bringing short cold spells, as well as unusual midwinter warmth.

The overall trend is towards later snow cover and earlier thaws.

Last year a summer drought led to a shortage of food for the reindeer, and in December, not enough snow.

According to Tim Horstkotte, a postdoctoral researcher at the Swedish Agricultural University (SLU), changing weather patterns are threatening the livelihood Sami herders have pursued for thousands of years.

“One of the things with climate change is that it gets so unpredictable,” he says. “Reindeer herders are quick to point out that it becomes unstable and unreliable. It’s impossible almost to plan ahead because things can change so dramatically in a short time.”