Light pollution at night is on an alarming rise worldwide, despite a transition to energy-saving LED lights, a new study has found.
Satellite images showed that the artificially lit surface of our planet grew by 2.2 percent per year in both size and brightness from 2012 to 2016, according to the study in the U.S. journal Science Advances.
The findings, released this week, were based on data from the first-ever calibrated satellite radiometer designed especially for nightlights, known as Visible Infrared Imaging Radiometer (VIIRS), which is mounted on a U.S. satellite that has been circling our planet since October 2011.
Globally, the increase in light emission closely corresponds to the increase of the Gross Domestic Product (GDP), with the fastest growth occurring in developing countries.
Still, researchers noted they may underestimate the problem of light pollution, because the VIIRS instrument used in this study can not "see" light at wavelengths below 500 nanometers, something called "blue" light, which humans can see.
"Earth's night is getting brighter. And I actually didn't expect it to be so uniformly true that so many countries would be getting brighter," Christopher Kyba from the GFZ German Research Centre for Geoscience, who led the study, told reporters at a news teleconference.
The study found that lighting changes varied greatly by country, far exceeding the global rate in some cases, and with decreases in radiance in only a few, such as war-torn Yemen and Syria, said the study.
In some of the world's brightest nations, like the United States and Spain, radiance remained stable, while for most nations in South America, Africa and Asia, it grew, it said.
The study is among the first to examine the effects, as seen from space, of the ongoing worldwide transition to LED lighting, which requires significantly less electricity to yield the same quantity of light as older lighting technologies.
Proponents of LED lighting have argued that the high energy efficiency of LEDs would contribute to slowing overall global energy demand, given that outdoor lighting accounts for a significant fraction of the nighttime energy budget of the typical world city.
"While we know that LEDs save energy in specific projects, for example when a city transitions all of its street lighting from sodium lamps to LED, when we look at our data and we look at the national and the global level, it indicates that these savings are being offset by either new or brighter lights in other places," Kyba said.
Kyba expected that the upward global trend in use of outdoor lighting will continue, bringing a host of negative environmental consequences.
"There is a potential for the solid-state lighting revolution to save energy and reduce light pollution," he said. "But only if we don't spend the savings on new light."
The researchers warned that "loss of night" on a planetary scale could cause negative effects on human health, ecosystems and even astronomical research.
"This is concerning, of course," said Frank Holker of the Leibniz Institute of Freshwater Ecology and Inland Fisheries in Berlin, a co-author of the study.
"We are convinced that artificial light is an environmental pollutant with ecological and evolutionary implications for many organisms from bacteria to mammals, including us humans and may reshape entire social ecological systems."
The Arizona-based International Dark-Sky Association (IDA) has campaigned for the last 30 years to bring attention to the known and suspected hazards associated with the use of artificial light at night.
"Today's announcement validates the message IDA has communicated for years," IDA Executive Director Scott Feierabend said. "We hope that the results further sound the alarm about the many unintended consequences of the unchecked use of artificial light at night."