According to a paper written by scientists in the journal Monthly Notices of the Royal Astronomical Society, they used a new instrument to study how clouds affect sky brightness in urban areas, and how the future of LED lighting might change the night time sky.

With Light pollution has become a growing problem, and skylines continue to grow, the night sky becomes dimmer and dimmer. However, researchers estimate that that night time sky could become bluer thanks to LED lighting.

Christopher Kyba, physicist at the Freie Universität and lead author of the study, said in a press release that , “The current worldwide trend of replacing gas discharge lamps with solid state lighting, such as LEDs, will affect the radiance and spectrum of urban skyglow.”

Franz Hölker, ecologist at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries and study author, said for nearly all of evolutionary history, clouds have made the night sky darker, just like what we witness during the day time.

However, in areas with artificial light, the effect of clouds is now reversed, and the size of the effect depends on the color. The team found that in Berlin, the blue portion of skyglow is 7 times more radiant on cloudy nights than on clear nights, and 18 times more for the red part.

The authors say that cloudy skies are now thousands of times more radiant near cities than they ever have been before. They believe the addition of this extra light affects predatory-prey relationships where the predator hunts using vision.

The sky is blue in daytime because the cloud free atmosphere is good at scattering short wavelengths of light. The scientists believe that unless special care is taken in design and implementation, a switch to whiter LED lights could make the sky brighter on clear nights.

The team believes that cities that have changed to solid state lighting should purchase lamps that emit no upward light, and use “warm white” lights with as little blue light as possible.