New research shows that American cities emit far more light per capita than comparably sized German cities. The results could help identify areas where light could be used more efficiently and minimise the negative impact of artificial light on the nighttime environment.
The researchers found that the differences between the American and German cities became more pronounced with city size: while light per capita increased the larger the city in the United States, it actually decreased as city size grew in Germany.
Lead author of the study, Dr. Christoph Kyba of the German Research Centre for Geosciences (GFZ), said that the difference in light emission is surprisingly large, and the researchers hope to use the results to uncover the reasons behind the differences. These could include differences in the type of lamps used, the width of streets (which would require more or brighter lighting) or the amount of trees. LED streetlamps, for instance, generally reduce the amount of light that shines upwards.
The study also found that the brightest light sources in megacities in developing countries were typically airports or harbours, where the brightest areas in Europe’s capital cities were oftentimes associated with leisure activities, for instance city centres or stadiums.
According to co-author Dr. Franz Hölker from the Leibniz Institute for Freshwater Ecology and Inland Fisheries, since artificial light is responsible for a sizable portion of all nighttime electricity consumption, the data provides information about which areas can best be targeted for energy savings.
Photo credit: NASA Earth Observatory/NOAA NGDC