Five years of advanced satellite images show that there is more artificial light at night across the globe, and that light at night is getting brighter. The rate of growth is approximately two percent each year in both the amount of areas lit and the radiance of the light.
A Brightening World
An international team of scientists on Wednesday reported the results of a landmark study of global light pollution and the rise of light-emitting diode (LED) outdoor lighting technology. The study, published today in the journal Science Advances, finds both light pollution and energy consumption by lighting steadily increasing over much of the planet. The findings also challenge the assumption that increases in the energy efficiency of outdoor lighting technologies necessarily lead to an overall decrease in global energy consumption.
The team, led by Dr. Christopher Kyba of the GFZ German Research Center for Geosciences in Potsdam, Germany, analyzed five years of images from the Suomi National Polar-orbiting Partnership satellite, operated jointly by the U.S. National Aeronautics and Space Administration and the National Oceanic and Atmospheric Administration. The data show gains of two percent per year in both the amount of the Earth’s surface that is artificially lit at night and the quantity of light emitted by outdoor lighting. Increases were seen almost everywhere the team looked, with some of the largest gains in regions that were previously unlit.
“Light is growing most rapidly in places that didn’t have a lot of light to start with,” Kyba noted. “That means that the fastest rates of increase are occurring in places that so far hadn’t been very strongly affected by light pollution.”
The results reported today confirm suggestions in earlier research based on data obtained with U.S. Department of Defense meteorological satellite measurements going back to the 1970s. However, the better sensitivity of Suomi’s cameras to light on the night side of Earth and significantly improved ground resolution led to more robust conclusions about the changing illumination of the world at night.
The study is among the first to examine the effects, as seen from space, of the ongoing worldwide transition to LED lighting. Kyba’s team found that the energy saving effects of LED lighting on country-level energy budgets are lower than expected from the increase in the efficiency of LEDs compared to older lamps.