Light pollution: Earth not uniformly brighter, Europe getting darker
Due to increasing urbanization, the night side of Earth is getting brighter every year. However, this is happening much more unevenly than previously assumed.
The night side of Earth, golden areas have become brighter recently, while violet areas have become darker
(Image: Michala Garrison / NASA Earth Observatory)
Although Earth has become noticeably brighter in recent years due to human activities, this has happened much more unevenly than previously assumed. This is the result of a newly presented study, for which brightness changes in human settlements were collected and evaluated in more detail and at a much higher frequency. Overall, nighttime lighting on Earth has increased by 16 percent between 2014 and 2022, with China accounting for a third of this alone. However, France has become a third darker during this period, primarily because streetlights are switched off there in many places after midnight. In Germany, light emissions have remained approximately constant.
Individual events visible from space
The study thus shows a much more dynamic planet, where measures against light pollution have measurable effects. According to Ruhr University Bochum, where Christopher Kyba participated as an expert in nighttime light remote sensing, this is based on the evaluation of data for individual days. Previously, such work has been based on monthly and annual data, which made it difficult to detect changes. Furthermore, a specially developed algorithm was used for the work now presented, which could consider the viewing angle of the satellite that made the respective recording. Fluctuations in brightness based on this have therefore been calculated for the first time in the work published in Nature.
Zhe Zhu from the University of Connecticut says that the revealed dynamics can be interpreted as the “heartbeat of society.” The data clearly show, for example, the sharp decrease in brightness in Ukraine after the major Russian attack in early 2022. The conflicts in Syria and Yemen are also clearly visible at night shots. One can even see exactly when and where the lockdowns in the fight against the corona pandemic came into force, writes the US university. At the same time, the data show the success of European measures against light pollution and for saving electricity. This is because the decrease in brightness here is not only due to the regulation of nighttime lighting, but also, among other things, to the switch to LED lights.
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Anyone who wants to view the determined data in detail can do so on a specially set up internet portal. On a world map, you can zoom into individual cities or settlements and view abrupt and gradual changes in nighttime brightness. For example, you can see that the center of Berlin has become noticeably darker after midnight between 2014 and 2022, while the outskirts have become brighter. At the same time, the metropolises of Paris and London have become significantly darker almost everywhere, with positive consequences for people and the environment. Kyba wants to research this further and therefore intends to propose to the European Space Agency ESA to develop a special Earth observation satellite and send it into space.
(mho)
