Friday, February 16, 2007

Weather is Complex

The weather is complex. See BBC Weather at and

“Historical evidence shows that the climate of the world since the planet was formed more than 4,000 million years ago has fluctuated greatly, and on many occasions has borne little resemblance to what we experience today.”

“More average conditions would be significantly warmer, producing the lush vegetation and hot conditions that prevailed aeons ago when dinosaurs walked the Earth for millions of years.”

“Throughout the history of the Earth it has been unusual to have one polar ice-cap; it is unique for us now to have two of them.” “the land mass that has become known to us as Antarctica has temporarily (in global terms!) positioned itself over the South Pole thereby blocking off warm currents.” “by another quirk of the slow drift of the continents, land has encircled the North pole, causing the waters there to be largely cut off from the worldwide drift of oceanic currents. This too has allowed an ice-cap to develop at the North Pole.”

“At the moment the Earth is passing through an interglacial which has lasted for around 10,000 years following the last Ice Age, which in turn went on for some 100,000 years.” “Perhaps ominously for man, the pattern suggests that ice ages last around 100,000 years on average and the shorter, warmer interglacials around 10,000 – so we are nearing the end of our current warmer period.”

“However, there is no need for any alarm at this thought. The next ice age could be up to 1,000 years or more away – a short period in climatology but a comfortingly lengthy one for us. And in any case no one can yet predict what effect the greenhouse effect may have on the overall pattern of global cooling and in arresting a return to glacial conditions.

“within the current interglacial, starting some 10,000 years ago, there have been smaller patterns emerging – periods of warmer weather, followed by colder weather and so on.” “probably reached its warmest about 5,000 or 6,000 years ago. At this time the temperature would have been on average about 2C (3.6F) warmer than the present day.” “This period has acquired the name the Optimum period as a result, and was followed by a much colder spell which more or less coincides with the historical period called the Iron Age, which reached its coldest around 2,500 years ago.”

“Ice ages should be seen on Earth as the norm rather than the exception. That is to say that with the present continental arrangements balanced against the heat source from the sun, it is to be expected that ice ages will occur.”

“The Earth's orbit changes from being almost a perfect circle to its elliptical form and then back again. This pattern can take around 100,000 years. Similarly, the Earth's tilt does not remain fixed at 66.5° to the plane but varies between 65.6° and 68.2° over a period of 40,000 years. At present the tilt is increasing.”

“analysis of climatic history suggests that this indeed is what has happened in practice and that it is these orbital variations that account for our weather pattern during the present ice epoch.”

Most of those calling for increasing the size and power of government to get the weather back to “normal” do not appreciate the complexity of weather. I doubt that many of them can explain the concept relative humidity.


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