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17 Jun 2002
An atlas that charts global light pollution reveals that only two-thirds of the world population see clear night skies.
Researchers from the Italian University of Padua and the National Geophysical Data Center, Colorado, US have compiled the First World Atlas of Artificial Night Sky Brightness. By collating data from US airforce defense meteorological satellites, Cinzano and colleagues calculated how artificial light propagates through the atmosphere. Their maps reveal the extent of light pollution around the world.
"The atlas provides a global picture of how mankind is proceeding to envelop itself in luminous fog," said Cinzano. "Large numbers of people in many countries have had their vision of the night sky severely degraded. Our atlas refers to the situation in 1996 to 1997, undoubtedly this is worse today."
To construct their maps the researchers used cloud-free images taken by oscillating scan radiometers that were housed in the satellites. The radiometers measured visible low light from artificial sources, such as mercury vapor and sodium lamps, which meant Cinzano and his colleagues could calculate average radiances given off by artificial light around the world. By comparing their results with population-density databases the researchers determined which of us see star-lit or artificially lit skies at night.
"Ninety nine per cent of the population in the US and European Union suffer from some degree of light pollution," said Cinzano. "More than one-fifth of the world and more than two-thirds of the US population have already lost naked-eye visibility of the Milky Way."
Cinzano highlights that light pollution is not just confined to developed countries, but is a global problem that affects nearly every country around the world.
"Many areas that were believed to be unpolluted show artificial brightness levels from the outward propagation of light pollution," he said. "In some cases one country's sky appears to be polluted by sources in a neighbouring country, this could open a new chapter of international jurisprudence."
Cinzano also says that Venice, Italy, showed comparatively low levels of artificial brightness. "This is due mainly to the unique low-intensity romantic lighting of this city, which deserves to be preserved," he said.
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