The Source of Europe's Mild Climate

The notion that the Gulf Stream is responsible for keeping Europe anomalously warm turns out to be a myth

Richard Seager

The Longevity of a Legend

When Battisti and I had finished our study of the influence of the Gulf Stream, we were left with a certain sense of deflation: Pretty much everything we had found could have been concluded on the basis of results that were already available. Ngar-Cheung Lau of the National Atmospheric and Oceanic Administration's Geophysical Fluid Dynamics Laboratory (GFDL) and Princeton University had published in 1979 an observational study in which he quantitatively demonstrated the warming and cooling effects that large-scale waves in the atmosphere had in Europe and eastern North America, respectively. In the 1980s, atmosphere modelers such as Brian J. Hoskins and Paul J. Valdes at the University of Reading in England and Isaac M. Held and Sumant Nigam at GFDL had shown how such stationary waves, including those forced by mountains, warm western Europe. In the late 1980s, two other GFDL researchers, Syukuro Manabe and Ronald J. Stouffer, had used a coupled ocean-atmosphere climate model to determine the climate impacts of an imposed shutdown of the North Atlantic thermohaline circulation. Their modeled climate cooled by a few degrees on both sides of the Atlantic and left the much larger difference in temperature across the ocean unchanged. Other published model experiments went on to show the same thing. Further, the distinction between maritime and continental climates had been a standard of climatology for decades, even centuries. What is more, by the late 1990s satellite data, and analyses of numerical models into which those data had been assimilated as part of the weather-forecasting process, had shown that in mid-latitudes the poleward transport of heat by the atmosphere exceeds that by the ocean several-fold.

All Battisti and I did was put these pieces of evidence together and add in a few more illustrative numerical experiments. Why hadn't anyone done that before? Why had these collective studies not already led to the demise of claims in the media and scientific papers alike that the Gulf Stream keeps Europe's climate just this side of glaciation? It seems this particular myth has grown to such a massive size that it exerts a great deal of pull on the minds of otherwise discerning people.

This is not just an academic issue. The play that the doomsday scenario has gotten in the media—even from seemingly reputable outlets such as the British Broadcasting Corporation—could be dismissed as attention-
grabbing sensationalism. But at root, it is the ignorance of how regional climates are determined that allows this misinformation to gain such traction. Maury should not be faulted; he could hardly have known better. The blame lies with modern-day climate scientists who either continue to promulgate the Gulf Stream-climate myth or who decline to clarify the relative roles of atmosphere and ocean in determining European climate. This abdication of responsibility leaves decades of folk wisdom unchallenged, still dominating the front pages, airwaves and Internet, ensuring that a well-worn piece of climatological nonsense will be passed down to yet another generation.

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