Opposite climate changes in Northwestern Europe

E. Linacre


Since the end of the last Ice Age, northwestern Europe has experienced more rapid and more intense climate variations than elsewhere. During the last Ice Age several rapid changes of sea surface temperature around Iceland, by as much as 7K in 100 years, have been revealed by cores of ocean sediment (1). Apparently these changes resulted from flip-flops between alternative patterns of global deep-ocean circulation. At the end of the last Ice Age, around 11.7 kBP, a sudden, short-lived cooling event affected northwestern Europe (2). This period, the younger Dryas, resulted when the meltwaters of the Laurentide Iceshield cooled the Labrador current, pushing it further south along the east coast of North America. This cold current pushed the warm Gulf Stream eastwards, so that it no longer reached latitudes of Europe north of Spain. As a consequence, the west winds from the cooled Atlantic onto northern Europe would lower temperatures there. The Younger Dryas is one of several cold spells affecting northwestern Europe, each lasting a few centuries, and each of these spells could have been triggered by pulses of freshwater inflow along North America's east coast (2).

A similar change may offset the current greenhouse-gas-induced warming in northwestern Europe. This would be the consequence of a series of events, as follows. Global warming implies warmer oceans and hence more evaporation. This would lead to more moisture in the atmosphere and hence an increased rate of precipitation, roughly matching the evaporation rate. The greater snowfall onto Greenland would enhance glacier flow and the calving of icebergs, which has, indeed, already been observed in recent decades. These would be carried south in the Labrador Current, cooling it further, and blocking the northward propagation of the Gulf Stream.

Alternatively, the blocking of the Gulf Stream could result from reduced deep-water formation in the north Atlantic (3). The subsidence from the surface to a depth of about 2 km results from the density of a surface-water. This water is a mixture of the Gulf Stream (which is relatively salty after evaporation at low latitudes) and inflows of fresh water from rivers and glaciers in Canada and Greenland. Now imagine an enhanced freshwater influx off N. America, either because of the melting of the Laurentide Iceshield, or because of increased rainfall and run-off in a warmer global climate. The mixture’s density would be reduced by the extra freshwater inflow, and subsidence could stop. That would alter the path of the Gulf Stream, leading to lower temperatures in Europe. In other words, global warming would paradoxically cause cooling in Europe. Also, stopping of subsidence would end the sequestration of atmospheric carbon dioxide in Bottom Waters, so that atmospheric CO2 concentrations would rise faster.

The moral is that global warming is unlikely to be uniform. Also, cooling in one area does not disprove global warming generally.

To learn more about rapid climate changes after the last glacial maximum, listen to this radio presentation at National Public Radio (USA).



  1. Bryant, E. 1997. Climate Process and Change (Cambridge Univ. Press), 802pp.
  2. Houghton, J. 1994. Global Warming: the complete briefing (Lion Publishing plc, Oxford) 192pp.
  3. Rahmsdorf, S. 1997. Risk of sea change in the Atlantic. Nature, 388, 825-6.