Humanity's efforts to vanquish the night and impose a dull glow above from dusk to dawn continue to be wildly successful.
According to a study published last week in the journal Science Advances, artificial sources of light are both expanding and brightening at a rate of 2.2 percent per year. Unsurprisingly, the growth is occurring most rapidly in developing nations, particularly those with night skies previously untouched.
"Light is growing most rapidly in places that didn’t have a lot of light to start with," study lead Dr. Christopher Kyba, from the GFZ German Research Center for Geosciences in Potsdam, Germany, said in a press release. “That means that the fastest rates of increase are occurring in places that so far hadn’t been very strongly affected by light pollution."
Kyba and his team sourced their data over a period of four years using NOAA's Suomi NPP weather satellite. Thanks to a low-light instrument on board called the Visible Infrared Imaging Radiometer Suite (VIIRS), the researchers were able to observe light reflected from Earth's surface and atmosphere in multiple wavelengths.
A view of Europe's nighttime lights as captured over the course of several months in 2016. According to researchers, 99 percent of the European Union population lives in areas where the night sky is polluted. (Photo: NASA)
LEDs: A surprising culprit
Surprisingly, the study places some of the blame for the increase in artificial light on the switch from outdoor incandescent and fluorescent lights to LED lights. The cost savings from this more efficient technology, they report, have apparently spurred an increase in lighting more places previously facing low impact from light pollution.
“We’ll light something that we didn’t light before, like a bicycle path though a park or a section of highway leading outside of town that in the past wasn’t lit," Kyba told Phys.org. “And so all of those new uses of light offset, to some extent, the savings that you had.”
Because LED lights emit blue light, a wavelength not easily picked up by Suomi NPP's instruments, the researchers say the glow perceived by the human eye may actually be greater than what they've recorded.
"Blue light is preferentially scattered by air molecules, and so the higher the correlated color temperature (CCT), the greater the light pollution problem becomes," the site AGi32 reports. "It is for this reason that the International Dark Sky Association requires a maximum CCT (correlated color temperature) of 3000K for its Fixture Seal of Approval outdoor lighting certification program."
The researchers say that a shift in LEDs from blue to newer versions containing warmer reds and greens will help curb their pollution, as well as enhanced capabilities such as control systems to either dim or activate by motion only.
Why we need darkness
Reducing light pollution is not only critical for those who value a pristine view of the heavens, but for species that depend upon darkness for their very survival.
"In addition to threatening the 30% of vertebrates and more than 60% of invertebrates that are nocturnal, outdoor artificial light also affects plants and microorganisms and is increasingly suspected of affecting human health," the researchers added.
In the short term, the team expects the problem to grow worse, with artificial light further eroding the borders of those untouched regions still experiencing normal day/night cycles. There is hope, however, for the environmental benefits of LEDs to help, rather than exacerbate the problem.
"There is a potential for the solid-state lighting revolution to save energy and reduce light pollution," Kyba said, “but only if we don’t spend the savings on new light."