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Maps

The Worldwide Light-Pollution Plague

Up to 99 percent of Americans and Europeans live under artificially brightened skies, according to a new analysis.

Light pollution over Joshua Tree National Park in California. (Dan Duriscoe/NPS)

Where should you travel if you want killer views of the stars unblemished by artificial light?

Certainly not the U.S. or Europe, where nearly 100 percent of the population endures some form of light pollution. And maybe skip South America, Asia, and Australia, too, as their citizens are among the 80 percent globally that live under human-lit skies. Best head to Chad, Madagascar, or the Central African Republic; more than three-quarters of locals there enjoy views of a coal-black abyss stippled with glimmering, gaseous diamonds.

That’s according to a new reckoning from researchers at Italy’s Istituto di Scienza e Tecnologia dell’Inquinamento Luminoso, NOAA, the National Park Service, and elsewhere, who’ve built one of the most comprehensive atlases of global light pollution to date. They hope their work will set a benchmark for future generations struggling with day blending into night, as artificial brightness has been blamed for everything from killing millions of migrating birds to disrupting the human sleep cycle to messing with rain forests.

It’s also plain annoying for people who just want to star-gaze. The researchers estimate that one-third of the world’s 7.4 billion people can’t even see the Milky Way. And the persistent haze could get worse as more communities make the switch to LEDs. “Unless careful consideration is given to LED color and lighting levels,” says the Istituto’s Fabio Falchi, “this transition could unfortunately lead to a 2-3 fold increase in skyglow on clear nights.” Here’s more from a press release:

Light pollution is no longer merely an annoyance for astronomers; the artificial brightening of the night sky is profoundly altering a fundamental human experience—the opportunity for each person to view and ponder the sky above in evening hours….

The atlas shows that more than 80% of the world and more than 99% of the U.S. and Europe live under light polluted skies. (The authors considered “polluted” to be the level of brightness at which artificial light substantially obscures astronomical observations.) The atlas also reveals that in some places with high levels of light pollution, such as Singapore, people never experience conditions resembling true night because it is masked by artificial twilight; in such places, most of the population lives under skies so bright that their eyes cannot fully adapt to night vision.

Here are a few examples from the atlas of showing how artificial lights have conquered the night. They’re based on readings from the Suomi NPP satellite; warmer colors indicate areas with intense light adulteration.

Fabio Falchi et al.

About the Author

  • John Metcalfe
    John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.