We are sure many of you remember headlines similar to these: “Global Warming to Cause Next Ice Age!” or “Global Warming to Send Europe into a Deep Freeze!” In fact, next time New England or Europe has a cold winter, we’ll guarantee that you’ll see them again. The idea behind this scare story (and the premise of the climatefright film The Day After Tomorrow) is that the ocean’s thermohaline circulation (which among other things modestly warms the winter climate of western Europe) slows down, or even worse stops, sending the climate into disarray—all because of anthropogenic global warming. In the case of The Day After Tomorrow, this circulation shut down led to a flash freeze of the planet, while more “reasonable” climate alarmists at least give it a couple of decades to turn Europe into the icebox. But, in reality, things just don’t seem to be headed that way at all.

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“False Alarm: Atlantic Conveyor Belt Hasn’t Slowed Down After All” is the title of a “News of the Week” piece in this week’s (November 17, 2006) Science magazine by science writer Richard Kerr (for those with a subscription, you can view the whole story, here).

Kerr’s piece starts off with the line “A closer look at the Atlantic Ocean’s currents has confirmed what many oceanographers suspected all along: There’s no sign that the ocean’s heat-laden ‘conveyor’ is slowing.”

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You may remember a major study regarding the greenhouse debate that surfaced last Christmas season. Harry Bryden and two associates at the UK’s National Oceanography Centre had analyzed five decades of data regarding the ocean circulation of the North Atlantic. They concluded in Nature magazine that “The comparison suggests that the Atlantic meridional overturning circulation has slowed by about 30 percent between 1957 and 2004.” The greenhouse crusade went wild, the media produced widespread coverage of Bryden’s findings, and the public was warned that the oceanic response to the build up of greenhouse gases could produce catastrophic results, particularly for European countries.

The story was straight out of “The Day After Tomorrow.” We were all told that the meridional circulation of the Atlantic carries warm upper waters into the mid-to-high latitudes and returns cold deep water southward across the Equator. We all learned about the “thermohaline circulation” that is a critical component in the energy balance of the earth-atmosphere system. The Bryden et al. findings could only heighten fears that human activities were having a profound impact on air-sea interactions, and if you recall, this could only lead to climate disasters – the entire story was straight out of a movie set.

We at World Climate Report were skeptical and questioned immediately why a 30 percent reduction in the thermohaline circulation had not produced noticeable cooling effects in Europe, after all, a complete shutdown of the circulation is expected to cause a cooling of 4°C in Europe, according to some computer models. We pointed out that the literature on ocean circulation contained evidence that the thermohaline circulation may be strengthening, exactly opposite what Bryden et al. claimed to have found.

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Do you recall seeing the classic film Day After Tomorrow? The theme of the movie was that humans warmed the earth, the global hydrological cycle was severely disrupted, fresh water began flowing into the North Atlantic, the Gulf Stream slowed rather suddenly, and Europe, and then the rest of the world, plunged into a glacial state. If you did not get the message in that film, Al Gore raised the possibility in his recent thriller.

But one is hard pressed to find evidence to support the idea that this is a real possibility. While there are some articles in the professional literature suggesting that the freshening of the waters of the North Atlantic has already begun, the conclusions in these articles are far from being universally accepted, and even farther from being the last word. There also exist articles showing no theoretical or empirical evidence to support the Gulf Stream story as it is pitched by Gore and followers.
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