Nenet girl, Yamal Peninsula, Siberia.
The Nenet people of the Yamal peninsula are nomadic reindeer herders who live within the Arctic circle on the northern coast of Siberia. In summer they graze their herds on the tundra of the peninsula, and in winter as the ground freezes they move south to milder parts of the Siberian steppes. They use the frozen surface of the landscape to cross the numerous freshwater lakes and marshes of the peninsula, which in summer they catch fish in.
But things are changing. The Arctic is the most sensitive area of the planet to climate change. While global average temperature has risen by around 0.8 degrees, some parts of Siberia have warmed by as much as 5 or 6. And so the Nenet have noticed the ground is freezing later and later in the year - and in some places, not freezing at all. The reindeer herders have to wait longer and longer before they can move their animals south across frozen ground.
Here, on the frontiers of the world, the warming of Siberia is already threatening a way of life that has remained fairly constant for thousands of years. It's not only that the Nenet have to move later in the year - many of the freshwater lakes that dot the landscape are leaking away as the frozen walls of earth that contain the water melt, and collapse. And so the Nenet are also losing the fishing that provides one of their main sources of food.
Siberia is a landscape that's underpinned by frozen ground, called 'permafrost', but this ground is beginning to thaw. Off the coast, whole islands made of permafrost are literally disappearing as the arctic sea washes away the rapidly melting land. Melting permafrost is causing roads, pipelines and foundations to collapse across the country. Every year, there's an increase in the area of ground that melts in summer and the area that doesn't refreeze in winter.
This isn't just a problem in the Arctic. This melt has global implications, because it's going to speed up climate change.
Permafrost is like a giant frozen compost heap - full of dead plants, animals, trees and other carbon-rich organic matter, and in places it reaches 1.5km (one mile) deep. While it stays frozen, that carbon is locked up in the ground. But as the Arctic warms and the permafrost thaws, microbes start to break down that organic matter, releasing carbon dioxide and methane into the atmosphere.
Methane is a potent greenhouse gas - probably causing, tonne for tonne, around 25 times more global warming over a hundred years than carbon dioxide. By lighting escaping methane, scientists can capture dramatic images of plumes of flame bubbling up through holes cut into Siberian lakes.
These emissions are adding more and more greenhouse gases to the atmosphere, which is accelerating climate change. Permafrost contains massive amounts of carbon - probably about twice what's currently in the atmosphere, and about 5 times more than all the human-caused greenhouse gases we've released. While we don't have a really clear understanding of how much carbon might be released as the permafrost melts, it's fair to say that any extra greenhouse gases in the atmosphere from melting permafrost are bad news.
Because of the melting permafrost, what happens in the Arctic doesn't stay in the Arctic. And so we need strong political action from world leaders at Copenhagen. We need to control the warming that's leading the Arctic to melt away. It's probably too late to stop climate change ending the Nenet's traditional way of life for good. But if we don't act now, that's going to be the case for pretty much everyone.