Prospects for dark skies grow dimmer

The distinction between day and night is disappearing in the most heavily populated regions of the Earth, a rapid shift with profound consequences for human health and the environment, according to a recent paper in the journal Science Advances.

“We’re losing more and more of the night on a planetary scale,” journal editor Kip Hodges said in a teleconference on the paper’s findings.

From 2012 to 2016, the artificially lit area of the Earth’s surface grew by 2.2 percent per year, according to the study led by Christopher Kyba of the German Research Centre for Geosciences. Kyba and his team analyzed highresolution satellite imagery to measure the extent of artificial outdoor lighting at night. The study also found that areas of the planet already lit grew even brighter, increasing in luminosity at a rate of 2.2 percent per year.

“Earth’s night is getting brighter,” Kyba said. One of Kyba’s images shows the change in the amount of nighttime lighting from 2012 to 2016.

Much of the increase is concentrated in the Middle East and Asia. The observed “decrease” in western Australia is actually due to wildfires in 2012 that were visible from space.

These observations probably understate the true increase in lit areas and light intensity because the satellites used in the study are not sensitive to blue light wavelengths emitted by LED lights.

The trend shows no sign of relenting.