The balance of probability is that this is a real global-warming effect. It's not going to go back. If global warming really is found to be responsible for the melting of the Arctic, it has two sets of consequences - one direct, the other demonstrative. If scientists can point to a shrinking skein of ice floes where valiant explorers once walked with huskies, it will help them to wake up the world to the powerful changes that man-made climate change is capable of making to all our lives. Directly, the disappearance of the shiny white ice at the pole means the loss, for the planet, of a huge reflector, beaming the sun's heat back at it.
Open water is darker and absorbs heat better.
In other words, the loss of the ice would add to the rise in global temperatures. Another direct consequence is a particularly ugly one for Britain. Global warming is predicted to mean steadily rising temperatures for our islands, bringing Mediterranean balm to the south. But within 100 years, this could change. With the melting of the Arctic ice, some models say, the existing circulation of cold and hot, fresh and salt water in the Atlantic would be dramatically violated.