According to a report in the latest issue of Nature magazine, an international scientific research team analyzed satellite observation data and found that the overall brightness of artificial light at night around the world increased by 16% between 2014 and 2022. However, this trend is not universal. Some areas that have been hit by wars and natural disasters, as well as those countries that have implemented effective energy conservation and light pollution control policies, have shown a trend of "darkening".
Continuously increasing artificial light will bring about a series of problems, including affecting human sleep, disrupting the biological rhythms of animals and plants, exacerbating light pollution, and weakening starry sky visibility. However, research shows that changes in global nighttime brightness do not increase uniformly, but increase and decrease in different regions, forming a "puzzle-like" pattern. In 2022, the United States ranks first in the world in terms of total nighttime brightness, followed by China, India, Canada and Brazil.
From the perspective of driving factors, brightness growth mainly comes from accelerated urbanization, infrastructure expansion and rural electrification, with the most significant increases in sub-Saharan Africa and Southeast Asia. The decrease in brightness is divided into two categories: sudden dimming is mostly caused by natural disasters, power grid failures and armed conflicts; progressive dimming is mostly related to energy-saving policies and light pollution reduction measures. This trend is present in some parts of Europe.
The research team used imaging products from NASA's "Black Marble" night-light remote sensing system. This system is based on the observation data obtained by the visible infrared imaging radiometer group, and uses algorithms to eliminate interference factors such as moonlight, aurora, and cloud cover. Compared with previous studies that relied on annual or monthly synthetic data, this method can more accurately reflect changes in the nighttime light source on the surface.
However, current satellite sensors are not sensitive enough to the blue light band, and modern lighting widely uses white LED lights, which emit high blue light components. This means that the actual brightness increase in some areas may not be fully captured.
Previous research has shown that over the past decade, the brightness of the night sky in human-inhabited areas has increased by nearly 10% per year. This continuously increasing nighttime illumination is "erasing" the starry sky, having a profound impact on astronomical observations, human health and ecosystems.