On thin ice

Dr Steven Amstrup, chief scientist for Polar Bears International, recognises this denial of reality. He says that climate-warming sceptics tend to use the universally appealing polar bears as the litmus test. If they can “cherry pick” statistics to make it appear that polar bears are thriving, then what they are really saying is that global warming isn’t a problem.

Most scientists agree polar bears are in trouble. Arctic ice, polar bears’ habitat and hunting ground, is melting at a rate of about 13 per cent a decade.

In the Polar Basin area, where sea ice forms along the shore then retreats in summer, the ice is retreating further and further from the shore as the Arctic warms. The bears have a stark choice: they can fast until the ice returns in the autumn, or they can risk swimming vast, exhausting distances to reach the remaining pack ice, where there may well be no seals to hunt.

Dr Amstrup points out that the numbers of bears in the western Hudson Bay have already declined, due to the increasing delay in the autumn ice freeze-up. The bears are leaner, and fewer cubs are being born and surviving.

Dr Andrew Derocher, a professor of biological science at the University of Alberta, argues there is a risk to their future survival. He refers to the so-called “three generations rule”. For polar bears, three generations is between 36 to 45 years in the future, roughly half the lifetime of a human. Scientists predict rapid loss of sea ice within this timeframe unless greenhouse gas emissions are greatly reduced.

Carolyn Taylor

Wellbank

Broughty Ferry, Dundee