Light pollution worsening across the globe

By Ryan Jones Matthews

A study of satellite images of the Earth at night has found that global levels of light pollution (artificial light which is considered unnecessary and damaging) have greatly increased in recent years.

The study, published in the journal Science Advances by a team of researchers led by Dr Christopher Kyba, revealed that between 2012 and 2016, the brightness and extent of artificial light on the planet had increased by an average of 2% each year.

To measure the levels of light pollution, the scientists used satellite images taken by NASA’s VIIRS radiometer, an instrument specifically designed for measuring the brightness of Earth’s night-time light.

The research discovered that while levels of artificial light in some of the world’s “brightest nations” (such as America) remained the same, most African, Asian, and South American nations were getting significantly brighter. The global “loss of night”, the scientists said, is leading to “negative consequences for flora, fauna, and human well-being.”

The few countries in where levels of night-time artificial light had decreased included Yemen and Syria, where devastating wars have seriously impacted or destroyed much of urban infrastructure.

Dr Kyba, who studies the ecological impact of light pollution at the German Research Centre for Geoscience, said that the introduction of electrical light was “one of the most dramatic physical changes human beings have made to our environment.”

He and his research colleagues had initially thought they would observe a decrease in light pollution in more advanced areas because of their trend of switching from sodium bulbs, which consume more energy and emit orange light, to LEDs, which are more efficient and emit light on the blue part of the spectrum.

“I expected in wealthy countries – like the US, UK, and Germany – we’d see overall decreases in light, especially in brightly lit areas”, Dr. Kyba told the BBC. “Instead we see countries like the US staying the same and the UK and Germany becoming increasingly bright.”

Because NASA’s VIIRS radiometer is only able to measure red and infrared light, the increase in artificial light that people experience is even more than what the scientists were able to measure.

Light pollution affecting how we see the world is nothing new. In 1994, after an earthquake caused a city-wide power outage in Los Angeles, the Griffith Observatory received phone calls in the middle of the night by residents who were confused by “the strange sky they had seen after the earthquake”. What they were seeing was the Milky Way.

Dr Kyba explained that it was possible to dramatically decrease our night-time light levels without impairing our visibility.

“Human vision relies on contrast, not the amount of light,” he pointed out. “So by reducing contrast outdoors – avoiding glaring lamps – it is actually possible to have improved vision with less light. That could mean big energy savings – but our data show that on a national and global scale, this is not the direction we are heading.”

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