Ten days ago I received a letter from Cairn Energy, the British company at the centre of Greenpeace's current direct action in the Arctic. I was told that its drilling operation is "relatively straightforward" and that the blue whales, polar bears and kittiwakes in Baffin Bay are safe, because, according to Cairn, "our programme is conventional".

This industry has lost its grip on reality. Anyone who has seen the remarkable images coming from the Arctic over the last few days will know how unusual, dangerous and extreme this business has become. While icebergs the size of football stadiums are towed out of a rig's path, ships equipped with high-pressure water cannons blast smaller chunks into submission. And all the while the clock is ticking. As the winter freeze edges nearer, this frantic exploration company rushes to finish the job before sheet-ice cuts off the region completely.

One hundred and fifty years since the first oil well was drilled in the US, this industry has reached the end of the line. The Arctic is said to contain about 90bn barrels of recoverable oil, which is enough to keep the thirsty world going for oh, three or four years. As climate change warms the icy seas, more areas become accessible to drilling. As this oil is extracted and burned, the warming accelerates and more companies pile in. A neat circle, but one that risks engulfing us all.

Climate change is a clear and present danger, and a series of brutal "weather events" this year should serve as the final warning. We are careful to point out that no single flood, storm or drought can be blamed on climate change, but the trend is getting hard to ignore. We are faced with a choice: act with real urgency to move away from fossil fuels and develop the clean tools that will help us completely rebuild our economic system, or carry on squeezing out the last drops and hope for the best.

Cairn Energy is betting on the status quo. Its letter informs me that the company is basing its plans on an International Energy Agency report which suggests that, by 2030, fossil fuels will still supply about 80% of the world's energy. What it doesn't say is that this "scenario" - the most pessimistic of several the IEA has produced - could lead to six degrees of warming by the end of the century.

Six degrees sounds manageable. It is not. These companies are relying on us to keep quiet while they take humanity to the brink. Our climbers are on that rig with a simple message: Go beyond oil.