Could global warming halt the Gulf Stream? Could it bring about a new ice age?

The short answer is ‘No’. So long as the Atlantic is surrounded by continents, the Earth continues to turn, and the trade winds continue to blow, the Gulf Stream will exist - the Gulf Stream itself cannot stall. It is equally unlikely that man-made global warming will result in a global cooling comparable to that of the last ice age.

However, if we ask what causes the relatively mild climate enjoyed by western and northern Europe, compared with other areas of the same geographical latitude, the answer is more complex. The commonly accepted notion that ‘the Gulf Stream heats Europe’ is unfortunately too vague to be used to understand possible, abrupt changes in the climate. A part of the Gulf Stream extends as a relatively warm current into the high northern latitudes where it warms the atmosphere, thereby cooling and sinking into the deep ocean. The climate of western and northern Europe is thus a result of the interplay between warm surface currents and cold deep currents.

This pattern of currents could be interrupted as a result of global warming, leading to a cooling of western and northern Europe. This is not the same as halting the Gulf Stream however - for example, there is a current in the Pacific that corresponds to the Atlantic’s Gulf Stream, the Kuroshio, but this current has no corresponding sinking in high latitudes and as a result, the north-east Pacific is 3 to 5ºC colder than the north-east Atlantic. We could therefore expect an interruption in the deep circulation to lead to a cooling of this degree in the North Atlantic.

We know that such a change is possible in principle. Unfortunately we do not know with confidence what the probability of its occurrence is (one in a thousand? one in ten?), when we might expect it to happen (in fifty years? in two hundred years?), how quickly the transition could happen (a decade? two decades? a century?) or the important details of how it would change the climate of western and northern Europe (other than that it would be colder). However, since its initial cause is global warming (resulting from the strengthened greenhouse effect), we can discount the possibility that it will lead to a global cooling, let alone a cooling comparable to an ice age.

Scientists at the Max-Planck Institute for Meteorology and elsewhere are investigating the current interplay between surface and deep circulation in the Atlantic. They are also researching possible future changes and their effects on both global and European climate.


A comprehensive account of abrupt climate change, published by the National Research Council of the U.S. National Academy of Sciences, can be found here:
https://www.nap.edu/catalog/10136/abrupt-climate-change-inevitable-surprises