Science & Technology

Seeing fewer stars? LEDs might be increasing light pollution

New lighting technologies might have increased it by 10% every year in last decade, finds study

By Rohini Krishnamurthy
Published: Friday 20 January 2023
Light pollution has robbed 30% of the global stargazers of a good view of stellar bodies. Photo: iStock
Light pollution has robbed 30% of the global stargazers of a good view of stellar bodies. Photo: iStock Light pollution has robbed 30% of the global stargazers of a good view of stellar bodies. Photo: iStock

The dazzling starry nights might be becoming less bright thanks to increasing light pollution. The sky has been brightening by nearly 10 per cent annually in the last decade, dramatically reducing star visibility across the globe, according to a new study.

Consequently, 30 per cent of the global stargazers have been robbed of a good view of stellar bodies, the study published in journal Science noted.

“At this rate of change, a child born in a location where 250 stars were once visible would be able to see only around 100 by the time they turned 18,” Christopher Kyba, a researcher at the German Research Centre for Geosciences and lead author of the paper, said in a statement.

Read more: Satellites add to light pollution significantly, says new report

Increased light pollution is due to the growing population, expanding settlements and the use of new lighting technologies such as light-emitting diodes (LED), the study noted.

Researchers from Germany and the United States analysed 50,000 observations from citizen scientists between 2011 and 2022.

Based on the data, the team calculated that the sky brightness increased by 9.6 per cent yearly. 

“The number of stars reported by people was decreasing year after year,” Kyba told Down To Earth.

The team used a model to estimate the amount of artificial light needed to generate the reported results. Their analysis showed that the skyglow went up by 9.6 per cent yearly.

This is much higher than satellite-based estimates, which show that the sky brightness has increased by 2 per cent a year between 2012-2016.

Satellites do not catch blue light emitted from LEDs, which have increasingly grown popular in the last decade, Fabio Falchi and Salvador Bará, from Light Pollution Science and Technology Institute, wrote in a perspective in Science. They were not involved in the study.

The duo added that the most important message from the latest study is that light pollution is increasing, despite policymakers taking measures to control it.

Global LED market share rose to 47 per cent in 2019 from under 1 per cent in 2011, the findings stated.

The impacts of LEDs on skyglow have been debated previously. Some researchers predicted that transitioning from traditional lights to LEDs would be beneficial, while others countered that theory.  

The latter suspected the transition could lead to a rebound effect, which means LED’s high efficacy would cause the installation of more or brighter lights or longer hours of operation.

Kyba believes the light pollution problem stems from the improper use of LEDs rather than the technology itself. “LEDs, in fact, offer many potential benefits, like being able to dim or turn them off instantly,” he explained.

Read more: A wake-up call to reclaim the forgotten darkness in our lives

The experts recommended a few steps to address the issue. Using lights only when, where and in the amount needed and avoiding lights that have ultraviolet or very cold white (shades of blue) could help, Kyba noted.

Citing an example, he said a city could enforce a rule, asking advertisers to shut off signs after a set time or enforcing a brightness limit, like 80 candela per square metre in urban centres and 20 candela per square meter in rural areas. 

A higher participation of citizen scientists can help researchers identify light trends in much smaller regions.“That would help us identify areas that are doing better than average, and we could try to understand what they are doing differently,” he said.

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