Testing times for Arctic research with fireworks

The BBC visits the most northerly human settlement on earth to see how scientists are measuring changes to our atmosphere.

"No-one leaves the bar till I've got a gun!"

It is 3am, the sun is shining, and a polar bear has been spotted heading directly to the camp. Welcome to a typical Saturday night in Ny-Alesund.

Situated at 79 degrees North, Ny-Alesund is the world's most northern civilian human settlement, situated on the island of Spitsbergen - part of the Norwegian Svalbard archipelago - only 745 miles (1,200km) south of the North Pole.

A former coal-mining town, it has been converted into a sizable research center, with up to 170 scientists living and working alongside the town's 30 permanent staff. And much of the research work is looking at changes in the climate.

Bendik Halgunset, research advisor on the base and, right now, the man responsible for keeping us alive, comes back with a hunting rifle and - as I discover - a live round in the chamber.

"It's for your own protection," he says. "The bears, they can move very fast."

Escorted back to our rooms, we go to sleep - as best you can in broad daylight - to the "crump" and "thump" of fireworks designed to scare the bear away.

The base is an international one. The UK and eight other nations have a permanent presence on the base, although many units are only manned during the summer.

Being so far north has its advantages: researchers are in a near-pristine environment at the top of the world, enabling them to accurately measure changes in levels of carbon dioxide, dust, soot, and chemicals such as PCBs.

Five hundred metres above the camp is the Zeppelin Mountain Station that measures changes in atmospheric gases and pollutants. And the only way you can get to it is via a 20-year-old cable car which - we are assured - is "quite safe if a little wobbly". Click here to read the full story.