Being well adjusted, in the 21st Century, means taking some pretty odd things in your stride. Eggs are a health food one week, poison the next; India's cows have their very own Bill of Rights; it's against the law to stare at the mayor of Paris; Yasser Arafat won the Nobel Peace Prize in 1994 . oh, life can be a bumpy little ride, for sure.

Global warming is another concept that is difficult to get your head around, not least because you just never know what's coming next. On that subject, I regret to tell you that if you think you've just managed to adjust nicely to the idea that we're in for warmer winters and higher tides, guess again! The fact is, we may be in for an ice age at any moment . really. I may be laughing, but I'm not joking. The warning comes from one of the most respected oceanographers in the business.

Here's the way it works - everyone knows that the Gulf Stream is a surface current that moves warm water from the Atlantic near the equator up to the cold regions of the North Atlantic, making them warmer than they might otherwise be. Since the prevailing winds flow from west to east, and carry the warm air around the Gulf Stream over to Europe, this also explains why London has appreciably warmer winters than New York, despite being on about the same latitude as Calgary and Edmonton. The Gulf Stream is like a river (actually, it's something like 75 times the size of the Amazon) moving a billion megawatts of heat from the area of the Gulf of Mexico up along the American coastline, then over to Europe.

What you may not know is that the Gulf Stream does not exist in isolation. It is pulled up to the north by something called ocean overturning, which is the sinking of cold, relatively salty water into the depths of the North Atlantic, powering a deep-water current that completes the circle by returning colder water to the South Atlantic. The technical term for this process, which is repeated in the South Atlantic and elsewhere in the world, is thermohaline circulation. The whole web of currents around the world, heating the north and cooling the south, is known as the Great Ocean Conveyor.

What oceanographers are beginning to suspect is that this system is now in the process of slowing dramatically, and may stop altogether.

What happens if the Conveyer ceases to convey? It has happened before - climactic records of one kind or another can be found in a variety of places on the earth, so we know more or less what takes place. About 12,800 years ago, the waters in the North Atlantic, and the land around that region, cooled quite dramatically. The process took about a decade to complete, and the resulting cold spell, called the Younger Dryas, lasted for about 1,300 years.

These cold snaps are not unusual, apparently. Past warm-to-cold transitions have taken between three and ten years to set in, and have lasted for between 500 and 1,000 years. Dr. Robert Gagosian, the president and director of the Woods Hole Oceanographic Institution in Woods Hole, Massachusetts, confirmed this Conveyer phenomenon in an article published recently that is available on the Woods Hole website. For some reason, it is difficult to capture the precise URL on the Woods Hole website. But if you search on the words "ice age" from the home page, at http://www.whoi.edu/home/, you will find it as the second entry in the list of answers.

In his article, Dr. Gagosian recalled that about 1,000 years ago, during a period of unusually warm temperatures in the North Atlantic, the Norse established settlements and even vineyards in Greenland that would not be possible today. Those settlements were abandoned about 500 years ago, when it is believed the most recent shutdown of the North Atlantic Ocean circulation system occurred.

During that era, called the Little Ice Age, Northern Europe was much colder than it is today, he said. Glaciers spread outward and downward in the Alps. Winters, on average, were more severe. Farming was affected. Famine was frequent.

"And in the 1730s and 1740s, abrupt European cooling caused famine across Western Europe, especially in Ireland and France, where farmers depended on wheat and potatoes. In Ireland, this is known as the "forgotten famine". As many people died during the forgotten famine as died during the famed potato famine of the 1840s.

"In the past year," he said, "oceanographers monitoring and analysing water conditions in the North Atlantic, have concluded that the North Atlantic has been freshening dramatically especially in the past decade. New data from Ruth Curry at Woods Hole Oceanographic Institution and her colleague Robert Dickson at the British Centre for Environment, Fisheries, and Aquaculture Science chronicles salinity changes in the western North Atlantic since 1960.

"The Great Ocean Conveyor transports fresh surface water down into the depths. The depths can absorb a lot of fresh water like a sponge. But since 1970, the equivalent of an extra 20 feet of fresh water across the surface of the northern North Atlantic has been transported down into the ocean depths, most of that since 1990.

"A sponge that is three-quarters saturated can still absorb more water. But the moment that sponge is fully saturated, it can absorb no more water.

"At some point, the North Atlantic will no longer absorb any more fresh water. It will begin to pile up on the surface. When that happens, the Great Ocean Conveyor will be clogged. It will back up and cease functioning.

"The very recent freshening signal in the North Atlantic is arguably the biggest and most dramatic change in ocean property that has ever been measured in the global ocean. Already, surface waters in the Greenland Sea are sinking at a rate 20 percent slower than in the 1970s.

"At what percent will the Ocean Conveyor stop? 25 percent? 40 percent? 60 percent? This is not like a dimmer switch, but more like a light switch. It probably goes from "on" to "off".

"We can't yet determine the precise source or sources of this additional fresh water. Global warming may be melting glaciers, or Arctic sea ice. In recent decades, the volume of Arctic sea ice has decreased by 40 percent. And if North Atlantic sinking slows down, less salty Gulf Stream waters flow northward which exacerbates the situation.

"In February 2002, at a worldwide meeting of oceanographers, new data on North Atlantic freshening prompted many scientists to say that salinity levels in the North Atlantic are approaching a density very close to the critical point at which the waters will stop sinking. "One of my colleagues at Woods Hole, Terry Joyce, put it this way: "I'm in the dark as to how close to an edge or transition to a new ocean and climate regime we might be," he said. "But I know which way we are walking. We are walking toward the cliff."

"To that sentiment, I would add this: We are walking toward the edge of a cliff blindfolded. Our ability to understand the potential for future abrupt changes in climate is limited by our lack of understanding of the processes that control them." When scientists talk about an ice age in this case, they're not talking about a huge sheet of ice that will cover the whole of the Northern Hemisphere. What they expect, though, is an average winter-time drop in temperature of about five degrees Fahrenheit over much of the US, and ten degrees in the Northeastern US and in Europe. That may not sound like much until you start to think of the effect on such things as agriculture and transportation, and perhaps, on intricately-woven little ecosystems.

What might happen in Bermuda is a bit of a guess. Dr. Nick Bates, senior scientist and oceanographer at the Bermuda Biological Station for Research, reminded me last week of the enormous complexity of interconnected ocean and atmospheric systems that power weather.

BBSR is of course, closely connected to Woods Hole, and participates in many research programmes connected to the study of the oceans. BBSR's 45-year Hydrostation "S" deep ocean database, for example, is the longest- running continuous study of marine hydrography in the world. Complexity notwithstanding, I'll give it a guess, since no one else will. I predict that if the Conveyor stops conveying as predicted, and the temperature in the Northeastern US drops by ten degrees, ours will drop by half of that . give or take a little. So run and buy shares in Belco.that'll warm you up.

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