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Thursday, December 01, 2005

When Global Warming Isn't

Alarm over dramatic weakening of Gulf Stream
The powerful ocean current that bathes Britain and northern Europe in warm waters from the tropics has weakened dramatically in recent years, a consequence of global warming that could trigger more severe winters and cooler summers across the region, scientists warn today.
Here is the cause/effect relationship:
Global warming weakens the circulation because increased meltwater from Greenland and the Arctic icesheets along with greater river run-off from Russia pour into the northern Atlantic and make it less saline which in turn makes it harder for the cooler water to sink, in effect slowing down the engine that drives the current.
To me this story illustrates why global warming trends won't continue as projected. The earth's climate appears to self-adjust to dampen or even reverse trends. In this case, tempurature increases cause ice-sheet melting, which cause changes in weather patters that cause lower tempuratures which cause ice-sheet to increase. The author of the article makes a similar point:
The final impact of any cooling effect will depend on whether it outweighs the global warming that, paradoxically, is driving it.
The History Channel recently aired a show on the last mini-ice age in Europe, from about 1300-1600. Tempuratures were only a few degrees colder, but it had a dramatic effect on the people of Europe. They were not equiped to adapt to the changing climate and it literally cost millions of lives. The program did not address the underlying cause of the climate change, so I wonder if it could have been cause be a similar change in the Gulf Stream.

The article mentions that this has happened before, but doens't go into any more detail than this:
Although climate records suggest that the current has ground to a halt in the distant past...
Stories like this one are the reason I don't worry too much about global warming. The earth's climate is in a continual state of flux. It always has been and it always will be. I think our resources are better spent adapting to the changing climate than trying to figure out how we can change the climate itself.

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