German cities emit several times less light per capita than similarly sized American cities, according to new research published in the journal Remote Sensing.
Berlin, Germany, at night
Moreover, the differences in light emission become more dramatic as city size increases: Light per capita increases with city size in the U.S. but decreases in Germany. Factors such as the type of lamps used and architectural elements like the width of the streets and the amount of trees are likely behind the differences, the researchers say. Energy-efficient LED street lighting is currently being installed in many cities worldwide, and the researchers expect this to change the nighttime environment in many ways — for example, by reducing the amount of light that shines upward. The study also found that, in major cities in developing countries, the brightest light sources were typically airports or harbors, whereas the brightest areas in large European cities are often stadiums and city centers.