In his book 'After the Ice,' Anderson writes of a world in which Arctic ice has permanently melted and polar bears don't exist. He says the nightmare will likely come true in only decades.

It's hard to imagine a world in which polar bears don't exist in the wild. Alun Anderson, former editor-in-chief of New Scientist magazine, asserts that it most likely will occur in our lifetime.

In his book, "After the Ice: Life, Death, and Geopolitics in the New Arctic" (HarperCollins, 2009), Anderson takes a close look at the complicated past, present and future of the Arctic region, the area of Earth that he says is certain to feel the effects of global warming first and most powerfully.

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Alun Anderson responding to an interview question:

A big shock to me is that this melt is unstoppable now. In a relatively short time, the Arctic will be ice-free. Going from bright, white ice to black water should be a signal to the world that something is coming. As the ice is melting, it is changing weather patterns in the Northern Hemisphere.

As the ice melts, there will be a rise in sea level. Perhaps 3 feet. That may not sound like a lot, but if you look at a 1-foot rise and what happens -- it takes out chunks of cities.

As the ocean warms, it lets off greenhouse gases, which will warm the Earth further. As the permafrost thaws out, microorganisms get active and digest carbon. It will be a slow change, but it will give us centuries of further warming we can't stop.