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Wasted energy
 

In North America, the  energy spent in uselessly lighting up the sky costs about a billion dollars each year.  This is a pure waste of energy that also  increases greenhouse gas emissions when fossil fuels are used to produce the  electricity, which is generally the case.


Here in Quebec,  more light is produced per inhabitant than anywhere else in the world.  It has thus been estimated that 700 GWh  could be saved annually in this province by improving lighting management.  This amount of energy represents the annual  electric heating bill for about 20,000 homes.   All this waste costs over 50 million dollars per year!

 
In 1997, an association of astronomers requested that  light pollution be studied using observations made from DMSP weather satellites  belonging to the US Air Force.  This led  to the creation of the first light pollution atlas with images that allowed  analysis of the brightness of the sky.   The map above paints a picture of the situation in eastern North America.   Different colours represent the amount of light pollution according to  the Bortle scale, which is shown in the legend below.
(Cinzano, Falchi & Elvidge 2001; Isobe, Hamamura & Elvidge