Future climate change in North-Western Europe may come as a shock

North-Western Europe could be in for some sudden climatic surprises in the future, say scientists speaking at the launch of a new book on global environmental change.

North-Western Europe is kept warm by an ocean current known as the North Atlantic Current, an extension of the Gulf Stream which brings warm water from the tropics to the north. This current is sensitive to global warming and could slow down, or even break down as a result of increasing global temperatures.

Studies of Earth’s ancient climate show that the North Atlantic Current has changed repeatedly and dramatically in the past, resulting in massive and sudden regional climate changes.

“Rapid changes of up to 10 degrees Celsius in a decade have happened more than 20 times in the past 100,000 years,” says Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany.

“Many scientists are concerned that similar rapid shifts in ocean currents could be triggered again by global warming. We are not yet sure how warm it has to get before this happens, but once the threshold is crossed the consequences for North-Western Europe are likely to be severe,” says Rahmstorf. “The threshold may well lie within the range of warming expected under business-as-usual within this century.”

Scandinavia is most at risk. “With a collapse of the North Atlantic Current, Scandinavia would experience a rapid drop in temperatures,” says Rahmstorf. He is head of an international research project that studies the possible consequences for fisheries, forests and agriculture.

But such a sudden change is still preventable, says Rahmstorf. “If we start reducing emissions now to limit global warming, we can most likely prevent this from happening. The risk for unpleasant surprises increases the longer we wait.”

Another significant finding predicted by current climate models is that the Gulf Stream may be sensitive to the rate of global warming as well as to the extent of warming.

“Models predict that with a slower rate of warming, the Gulf Stream has the chance to adjust and reach an equilibrium. Faster rates of warming may lead to a sudden collapse of the system,” says Professor Thomas Stocker from the University of Bern in Switzerland.

The study has policy implications for governments attempting to tackle the greenhouse gas emissions issue. “Early action to curb greenhouse gas emissions could mean the difference between maintaining the Gulf Stream and markedly changing it, which leaves society more options regarding the emission paths to avoid a collapse of the Gulf Stream,” says Professor Stocker.