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Politics : The Environmentalist Thread
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To: Peter Dierks who wrote (6122)4/2/2006 7:35:23 AM
From: maceng2  Read Replies (5) of 36917
 
Until recently "global dimming" caused much concern. i.e. reducing the amount of sunlight getting to the Earths surface. The trend has reversed over the recent decade, mainly thought to be due to the break up of the Soviet Union and the disbandment of her heavy industries. Recent industrialization of India and China might reverse the trend again though.

news.bbc.co.uk

I don't know why the scientist in the BBC article was so "astonished" he must have spent his life half asleep. To anyone involved in the navigation of shipping at night the loss of visibility from pollution (over EVERY ocean) has been literally STARING THEM IN THE EYES for more then a half of a century.

Here is some data that has been used by businesses for the 20th century.

The formula used for the power of a ships navigation lights to be seen at a distance "D"

mcanet.mcga.gov.uk

I = 3.43[10^6]T[D^2][5^-D]

where

I= equals candela required of light source.
D= distance in nautical miles.
K= atmospheric transmissivity
T= threshold factor (2x[10^-7])

K is the factor in question. On a defined "clear dark night" K used to be set at 0.9. Absolute clean air was defined as K=1.0. During the late 1970's K=0.9 was found to exist on less then 5% of nights in European waters. The definition was lowered to K=0.8, and then (by both American and European authorities) to K=0.74 as the definition of a "clear dark night".

Thus it is proven beyond all reasonable doubt that by 1982 25% of our visibility (since 1912) had disappeared!

As said this "dimming" trend seems to have reversed for now.
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