New knowledge reveals how shortly gentle air pollution is clouding the evening sky

The night sky is brightening faster than researchers realized due to the use of artificial light at night.Study of over 50,000 stellar observations by citizen scientists shows The night sky is about 10% brighteron average, annually from 2011 to 2022.

In other words, babies born in regions with about 250 stars a night see only 100 stars by their 18th birthday, researchers report in the Jan. 20 issue of Science.

The harm of light pollution goes far beyond not being able to see so many stars.Too bright at night will endanger people’s healthsend Migratory birds fly into buildingsDisrupting Food Webs by Mapping pollinating insects towards the light rather than the plant, it might even interrupt the Fireflies try to have sex (Serial Number: 8/2/17; Serial Number: 8/12/15).

“In a way, it’s a call to action,” said astronomer Connie Walker of the National Optical-Infrared Astronomy Research Laboratory in Tucson. “People should consider that this does have an impact on our lives. It’s not just astronomy. It affects our health. It affects other animals that can’t speak for themselves.”

walker with earth at night The event began in the mid-2000s as an outreach program connecting students in Arizona and Chile and now has thousands of participants around the world. Contributors compare the stars they can see with maps of which stars can be seen under different levels of light pollution, and feed the results into the app.

“I’ve always been very skeptical of Globe at Night” as a tool for precise research, admits Christopher Kyba, a physicist at the GFZ German Research Center for Geosciences in Potsdam. But the power lies in the sheer numbers: Kyba and colleagues analyzed 51,351 individual data points collected from 2011 to 2022.

“Individual figures are imprecise, but there are many,” he said. “This Globe at Night project is not just a game; it’s very useful data. The more people involved, the stronger it gets.”

These data, combined with Global Sky Brightness Atlas published 2016allowing the team to conclude that the brightness of the night sky increased by an average of 9.6% per year from 2011 to 2022 (Serial Number: 6/10/16).

Satellites that collect brightness data around the globe missed most of the increase. Over the past decade, these measurements show an increase in brightness of only 2% per year.

There are several reasons for this, Kyba said. Since the early 2010s, many outdoor lights have switched from high pressure sodium bulbs to LEDs. LEDs are more energy efficient, providing environmental benefits and cost savings.

But LEDs also emit more short-wavelength blue light, which scatters particles in the atmosphere better than the orange light of sodium bulbs, creating more of a sky glow. Existing satellites are not sensitive to blue wavelengths, thus underestimating the light pollution from LEDs. Satellites can miss rays that shine toward the horizon, such as from signs or windows, rather than directly up or down.

Astronomer and light pollution researcher John Ballentine isn’t surprised that satellites have underestimated the problem. But “I’m still amazed at how undervalued it is,” he said. “This paper confirms that we have consistently underestimated light pollution in the world.”

The good news is that it doesn’t take a major technological breakthrough to help solve this problem. Scientists and policymakers just need to convince people to change the way they use lights at night — easier said than done.

“People sometimes say that light pollution is the easiest pollution to fix because you just flip a switch and it goes away,” Kyba said. “It does. But it ignores the societal issue — the overall problem of light pollution is the result of billions of individual decisions.”

Some simple solutions include dimming or turning off lights throughout the night, especially floodlights or lights in empty parking lots.

Kyba shared a story about a church in Slovenia that switched from four 400-watt floodlights to a single 58-watt LED that shone behind a cutout in the church to focus the light on the church’s facade. Kyba is in International Journal of Sustainable Lighting 2018. The church is still brightly litbut the grass, trees and sky around it are still dark.

“If it were possible to replicate this story over and over again in our society, it would show that you really can significantly reduce the light in the sky, still have a bright environment, and have better vision and use less energy ,” he said. “It’s a dream.”

Barentine, who leads a private dark-night consultancy, believes widespread awareness of the problem — and subsequent action — may be imminent.For comparison, he points to a well-known Oil slick fire on Cuyahoga RiverOutside Cleveland in 1969 fueled the environmental movement of the 1960s and 1970s and led to the passage of the Clean Water Act by the US Congress.

“I think we’re on the brink of light pollution,” he said.