Sunday, November 4, 2012

Climate Change Revisited

The recent weather catastrophe that struck an area of the United States where some fifty million individuals reside brings to the forefront once again the issue of climate change.  The storm surge precipitated by the hurricane referred to as, "Sandy," was unprecedented in its severity for this region of the country.  The damage that it wrought in both its physical manifestations and its emotional impact on the lives of those directly affected together with the mounting cumulative evidence including extreme hot weather, droughts, the frequency and severity of forest fires, etc. are representative of the expected consequences of the ever-increasing concentration of greenhouse gases in the atmosphere as predicted by sophisticated computer-modeling developed by climate scientists.   


I have eluded to some of these factors in previous reports, that show a connection between increased surface temperature of the oceans and the expected increased severity and possible frequency of hurricanes and typhoons that derive their energy from ocean temperature. I would like to take this opportunity, however, to address a very particular aspect of climate change that may directly relate to extreme weather conditions more likely to impact global weather patterns in the more distant future..


Since the upper layers of the ocean have direct interaction with the atmosphere, changes in this upper level have a direct bearing on climate over shorter periods of time (decades).  However, deep ocean circulation has a direct influence over future climate conditions.  For water to sink from the ocean's surface to the deeper ocean, it must be more dense – the two criteria that meet this requirement are temperature and salt content i.e. the water must be cold and salty.  The water in the Atlantic Ocean and the Greenland Sea – between Greenland and the Scandinavian countries –  and the ocean around Antarctica are large bodies of water that meet these requirements.  This deep dense water contributes to the deep water circulation that is global in extent.  This process is knows at the thermohaline circulation (THC).  It is important to understand that the THC influences global climate by transporting heat and freshwater between the oceans globally.


As ice melts as a direct consequence of the level of greenhouse gases in the atmosphere, the water in its immediate vicinity becomes less dense as a result of simple dilution.  As a consequence, such water will be less likely to sink to the deep ocean.  Consequently, this weakening of the THC, lessens the heat flow from the tropics to the North Atlantic.  It is anticipated that if the level of greenhouse gases is allowed to increase unabated over the long term, the THC would be expected to breakdown entirely.  If this should happen, the winters in the North Atlantic and Western Europe could be become extremely severe.


This kind of scientific analysis demonstrates that if humanity fails to address the problem of greenhouse gas emission in a meaningful way, both the near term and long term effects could prove disastrous to life as we know it. 

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