Reproduction of the press release from Ruhr University Bochum (with minor edits)

Summary

Viewed from a great distance in both space and time, the night-time glow of inhabited areas on Earth is steadily increasing. However, the hidden variability within in this overall change has been demonstrated by a new analysis of satellite data undertaken by a research team from the University of Connecticut, in collaboration with NASA and researchers in the U.S. and Germany. “For the first time, daily satellite images were used for this purpose on a global scale,” says Professor Christopher Kyba, professor of night-time light remote sensing at the Ruhr University Bochum, Germany. He participated in the study and made significant contributions to it at the GFZ Helmholtz Centre for Geosciences in Potsdam, where he had worked as a researcher until 2024. Dr Theres Kuester also contributed; she too worked at the GFZ as a researcher and guest researcher until 2024.

The data confirm earlier studies that light emissions are increasing overall. However, the most important new finding is that fluctuations occur frequently, and are not solely attributable to major factors such as the COVID-19 lockdowns or the war in Ukraine. The researchers reported their findings in the April 8, 2026, issue of the journal Nature. The article was featured as this week’s Nature cover story.

Surprisingly dynamic changes in lighting levels

An analysis of data from the VIIRS DNB satellite instrument covering the years 2014 to 2022 finds that night-time lighting is increasing globally by about two percent per year. “Although there has been a total increase of 16 percent worldwide, that does not mean that lighting is increasing everywhere,” explained Christopher Kyba. “In areas where lighting increased, we found global emissions rose by 34 percent. This was offset by an 18 percent decrease in emissions from other areas.” These local changes in lighting were much more dynamic than previously assumed. While China and India became increasingly brighter due to urbanization during the analysis period, measured emissions from other industrialized nations tended to decrease, for example because they switched to LED lighting or introduced regulations to curb light pollution.

The situation in Europe: a decline in night-time light emissions

A dramatic decline in lighting was observed in Ukraine following the Russian invasion. France also dimmed significantly at night (down 33 percent), as many municipalities there turn off streetlights after midnight to save energy and reduce light pollution. 

“In Germany, light emissions remained almost constant overall despite local variations,” Kyba reports. “While light emissions rose by 8.9 percent in brightening German regions, they fell by 9.2 percent in dimming areas.” 

Overall, night-time light emissions observed by the satellite in Europe declined by four percent—though this small decrease may not reflect the human experience, as there are differences between the sensitivity of this satellite instrument compared to human vision.

First global analysis at full resolution

These findings were made possible by analysing data from each individual night. Previous observations were based on monthly or annual composites, which due to instrumental factors made it more difficult to detect and measure changes. “Until now, no global analysis had been conducted using the full-resolution night-time data,” Kyba emphasizes. The researchers also made use of an algorithm that incorporates information about the satellite’s viewing angle into account. For example, residential areas usually appear brighter when viewed from an angle than when viewed from directly above, but the opposite is usually the case in city centres. The new analysis accounts for such differences for the first time.

The Satellite

The data analysed in the study were obtained from the Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) instrument aboard the Suomi NPP, NOAA-20, and NOAA-21 satellites operated by the U.S. agencies NOAA and NASA. The satellites observe after midnight, typically between 1:00 a.m. and 4:00 a.m. local time. They image the entire planet nightly between 70° North and 60° South. A single satellite pixel covers an area of approximately 0.5 square kilometres. In this analysis, only areas with artificial light were examined; forest fires and auroras are detected by the satellite but were excluded from the analysis.

A new satellite for Europe

“Artificial light is a major consumer of electricity at night, and light pollution harms ecosystems,” says Christopher Kyba. “It is therefore important to understand how both of these are changing.” Kyba is leading a team that is proposing a state-of-the-art satellite for observing night lights to be selected for the European Space Agency’s (ESA) “Earth Explorer 13” mission. This new satellite would be able to see much fainter lights than existing satellites and, thanks to its high resolution, would greatly reduce the current uncertainty about exactly what is changing. “While the U.S. and China each have multiple satellites that observe night-time light, there is currently no European satellite designed for this purpose,” says Kyba.

Funding

This work was supported by the Terra, Aqua, Suomi-NPP and NOAA-20 programs of NASA (grant 80NSSC22K0199) and the Remote Sensing Theory for Earth Science program of NASA (grant 80NSSC20K1748). Christopher Kyba was supported by the New Earth Observation Mission Ideas program of ESA (contract 4000139244/22/NL) and by the DFG (grant 545098235). The computational work for this project was conducted using resources provided by the Storrs High-Performance Computing (HPC) cluster.

(Text: Meike Drießen; Translation to EN: Christopher Kyba; Press release Ruhr-Universität Bochum)

Original publication

Li, T., Wang, Z., Kyba, C.C.M. et al. Satellite imagery reveals increasing volatility in human night-time activity. Nature 652, 379–386 (2026). https://doi.org/10.1038/s41586-026-10260-w

Further information:

A video of the variability of Earth light pollution since 2014 is shown on the University of Connecticut website.

Scientific Contact

Prof. Dr Christopher Kyba
Nighttime lights remote sensing
Faculty of Geography and Geosciences
Ruhr University Bochum
Germany
Phone: +49 234 32 18088
Email: christopher.kyba@ruhr-uni-bochum.de

Prof. Dr Zhe Zhu
Remote Sensing
Department of Natural Resources & the Environment
University of Connecticut
Phone: +1 860 486 6885
Email: zhe@uconn.edu