Wednesday, January 28, 2004

The Big Chill, a fluke or a forewarning?

Right now, things are cold out there. It's not that it's particularly cold compared to winter's of memory, but there's a pattern musing on the edge of the oldman's mind. The unprecedented (in modern times) heat wave in Europe this past summer that killed thousands of lives; the longest recorded stretch of time in Oklohoma without twisters (tornadoes); and now the artic blast that has frozen half the USA. The oldman had allot of time to think about it today as he drove through the teeth of a blizzard. There seems to be a pattern of extreme weather this past year, including the California fires, that while individually has precendent altogether raises some neck hair on the oldman's intuition.

Paul Epstein also has thoughts on the matter, in his op-ed in the NYT.

Normally, water circulates in the North Atlantic like this: Cold, salty water at the top sinks; that sinking water acts as a pump, pulling warm Gulf Stream water north and thus moderating winter weather. But now, fresh water from the thawing ice and heavier rain is accumulating near the ocean's surface; it's not sinking as quickly. (The tropics are faced with the opposite phenomenon. According to Dr. Ruth Curry and her colleagues at the Woods Hole Oceanographic Institution, the tropical Atlantic is becoming saltier; as warming increases, so does evaporation, which leaves behind salt.) The "freshening" in the North Atlantic may be contributing to a high-pressure system that is accelerating trans-Atlantic winds and deflecting the jet stream — changes that may be driving frigid fronts down the Eastern Seaboard. The ice-core records demonstrate that the North Atlantic can freshen to a point where the deep-water pump fails, warm water stops coming north, and the northern ocean suddenly freezes, as it did in the last Ice Age. No one can say if that is what will happen next. But since the 1950's, the best documented deep-water pump, between Iceland and Scotland, has slowed 20 percent.

Why now? After all, the planet's previous periods of global warming resulted from changes in the earth's tilt toward the sun, and recent calculations of these cycles indicate that our hospitable climate was not due to have ended any time soon. But because of the warming brought by the buildup of carbon dioxide, mainly from the burning of fossil fuels, the equations have changed. We are entering uncharted waters. It's something for New Yorkers to ponder as they bundle up.

The problem is that the atmospheric and metereological conditions don't respond linearly. It isn't as if one can put out one change, and then measure conditions to see how they will react. Changes in the environment often take years to have any significant impact, but this doesn't mean that the impacts are minor. Small incremental changes can over time suddenly result in a massive reactionary change. Think of earthquakes. Over time the crust of the earth moves in small increments, rubbing tectonic plates up against each other. This compaction builds up tremendous energy. Then one day it all cuts loose. Similarly often earthquakes are quiescent for decades or even centuries, but swell up and blow their tops in a matter of mere weeks or even days.

Not exactly pleasant thoughts to be thinking!


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