Oops, low energy leds are increasing light pollution

By Matt Williams

The city of Calgary, Alberta, as seen from space. - Image Credit: NASA

When it comes to technology and the environment, it often seems like it’s “one step forward, two steps back.” Basically, sometimes the new and innovative technologies that are intended correct for one set of problems inevitably lead to new ones. This appears to be the case with the transition to solid-state lighting technology, aka. the “lighting revolution”.

Basically, as nations transition from traditional lights to the energy-saving Light-Emitting Diodes (LEDs), there is the potential for a rebound effect. According to an international study led by Christopher Kyba from the GFZ German Research Center for Geoscience, the widespread use of LED lights could mean more usage and more light pollution, thus counter-acting their economic and environmental benefits.

The study, titled “Artificially Lit Surface of Earth at Night Increasing in Radiance and Extent“, recently appeared in the journal Science Advances. Led by Christopher C. M. Kyba, the team also included members from the Leibniz Institute of Freshwater Ecology and Inland Fisheries, the Instituto de Astrofísica de Andalucía (CSIS), the Complutense University of Madrid, the University of Colorado, the University of Exeter, and the National Oceanic and Atmospheric Administration (NOAA).

Photograph of Calgary, Alberta, Canada, taken from the International Space Station on Nov. 27th, 2015. - Image Credit: NASA’s Earth Observatory/Kyba, GFZ

To put it simply, the cost-saving effects of LED lights make them attractive from a consumer standpoint. From an environmental standpoint, they are also attractive because they reduce our carbon footprint. Unfortunately, as more people are using them for residential, commercial and industrial purposes, overall energy consumption appears to be going up instead of down, leading to an increased environmental impact.

For the sake of their study, the team relied on satellite radiometer data calibrated for nightlights collected by the Visible/Infrared Imager Radiometer Suite (VIIRS), an instrument on the NOAA’s Suomi-NPP satellite that has been monitoring Earth since October of 2011. After examining data obtained between 2012 and 2016, the team noted a discernible increase in power consumption associated with LED use. As they explain in their study:

“[F]rom 2012 to 2016, Earth’s artificially lit outdoor area grew by 2.2% per year, with a total radiance growth of 1.8% per year. Continuously lit areas brightened at a rate of 2.2% per year. Large differences in national growth rates were observed, with lighting remaining stable or decreasing in only a few countries.”

This data is not consistent with energy reductions on a global scale, but rather an increase in light pollution. The increase corresponded to increases in the Gross Domestic Product (GDP) of the fastest-growing developing nations. Moreover, it was also found to be happening in developed nations. In all cases, increased power consumption and light pollution has natural consequences for plants, animals, and human well-being.

As Kevin Gaston – a professor from the Environment and Sustainability Institute at the University of Exeter and a co-author on the study – explained in a University of Exeter press release:

“The great hope was that LED lighting would lead to lower energy usage, but what we’re seeing is those savings being used for increased lighting. We’re not just seeing this in developing countries, but also in developed countries. For example, Britain is getting brighter. You now struggle to find anywhere in Europe with a natural night sky – without that sky glow we’re all familiar with.”

The team also compared the VIIRS data to photographs taken from the International Space Station (ISS) which showed that the Suomi-NPP satellite sometimes record a dimming of some cities. This is due to the fact that the sensor can’t pick up light at wavelengths below 500 nanometers (nm) – i.e. blue light. When cities replace orange lamps with white LEDs, they emit more radiation below 500 nm.

The effect of this is that cities that are at the same brightness or have experienced an increase in brightness may actually appear dimmer. In other words, even in cases where satellites are detecting less radiation coming from the surface, Earth’s night-time brightness is actually increasing. But before anyone gets to thinking that it’s all bad news, there is a ray of light (no pun!) to be found in this research.

The effects of light pollution across the globe, as seen from space. - Image Credit: NASA

In previous studies, Kyba has shown that light emissions per capita in the US are 3 to 5 times higher than that in Germany. As he indicated, this could be seen as a sign that prosperity and conservative light use can coexist:

“Other studies and the experience of cities like Tucson, Arizona, show that well designed LED lamps allow a two-third or more decrease of light emission without any noticeable effect for human perception. There is a potential for the solid state lighting revolution to save energy and reduce light pollution, but only if we don’t spend the savings on new light”.

Reducing humanity’s impact on Earth’s natural environment is challenging work; and in the end, many of the technologies we depend upon to reduce our footprint can have the opposite effect. However, if there’s one thing that can prevent this from continually happening, it’s research that helps us to identifies our bad habits (and fix them!)

Source: Universe Today - Further Reading: Eureka Alert!University of ExeterScience Advances


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