GoKawiilData and study area
The foundational dataset for this global analysis of ALAN dynamics was the Black Marble product suite of NASA (Collection 1), derived from the DNB sensor onboard the VIIRS instrument3. The DNB observes light in the wavelength range of 500–900 nm, with an equatorial local overpass time of roughly 1:30 a.m. Standardized quality assurance of the Black Marble data ensures consistency across time, geography and sensors (Suomi-NPP and the NOAA-20/NOAA-21VIIRS DNB), enabling cross-mission compatibility vital for continuous monitoring applications51. We acquired two specific daily products (that is, VNP46A2 and VNP46A1) from the NASA Level-1 and Atmosphere Archive and Distribution System Distributed Active Archive Center (LAADS DAAC), covering the period from 1 January 2013 to 31 December 2023.
The primary daily NTL data for detecting changes was the VNP46A2 product, which provides daily ALAN radiance values (nW cm−2 sr−1) corrected for atmospheric influences and bidirectional reflectance distribution function (BRDF) effects from lunar illumination geometry and diverse surface reflectance variability3. This rigorous design improves radiometric stability and distinguishes Black Marble from earlier NTL products, supporting quantitative, science-quality analysis. Data are provided in geographic coordinates (WGS84) at a nominal spatial resolution of 15 arc-seconds (about 460 m at the equator), finer than the intrinsic sensor resolution of about 750 m. Complementing this, we used the VNP46A1 products to provide the pixel-level quality assessment flags of cloud, snow/ice and solar/lunar contamination information21. These products also supplied detailed viewing geometry, specifically the sensor viewing zenith angle (VZA), a key parameter for the VZA-stratified COntinuous monitoring of Land Disturbance (VZA-COLD) change detection algorithm used to mitigate angular effects on observed NTL4.
To ensure high-quality inputs for the change detection algorithm and improve processing efficiency, two pre-processing steps were conducted: systematic filtering of low-quality daily images and masking of persistently dark areas with no historical artificial light (Supplementary Information Section 1). The ALAN change detection results were generated under the linear latitude/longitude geographic projection, consistent with the input atmospheric- and lunar-BRDF-corrected Black Marble data. This projection was also retained for visualizations of the global maps. However, all quantitative analyses in this study, such as area estimates and accuracy assessments, were conducted following the MODIS/VIIRS 500-m nominal resolution sinusoidal equal-area projection to ensure accurate area-based calculations.
The geographic scope of this study was defined as the global terrestrial regions located between 70° N and 60° S. This latitudinal range was chosen because it encompasses the vast majority of the landmasses of Earth and virtually all primary human settlements and areas of substantial ALAN52. Polar regions were excluded from the analysis because of data acquisition challenges (for example, polar day, extensive snow and ice). Oceans and large inland water bodies were masked using the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) Land Water Mask product in 2014 (MOD44W Collection 6.1)53. The World Bank Official Boundary data (accessed 1 January 2025) were used for regional aggregation (continents, countries, and territories). The core period for ALAN change detection was 1 January 2014 to 31 December 2022. Data from 2013 served for model initialization, and data from 2023 for confirming end-of-series changes (see details in Supplementary Information Section 1).
Definition of ALAN change types
In this study, ALAN changes are categorized into two primary types based on their temporal patterns: abrupt and gradual (Supplementary Fig. 4c). These are further classified as either brightening or dimming, depending on the direction of change in radiance. Abrupt ALAN changes are short-term shifts characterized by sudden step-like changes in NTL radiance or a structural break in the time series. These changes typically unfold over a span of weeks to months and often correspond to discrete events such as urban construction or demolition (Fig. 1c), natural disasters (Fig. 1h), or armed conflicts (Fig. 1d). Abrupt changes also include changes that caused sudden redirections of a longer-term trend, such as the onset of economic recession or a surge in foreign investment or immediate policy actions (for example, beginning of rapid lighting installation), leading to a noticeable inflection in the trajectory of ALAN dynamics (Fig. 1j). By contrast, gradual ALAN changes represent long-term, continuous trends that unfold over periods exceeding 1 year. These changes exhibit a relatively stable, directional pattern, either brightening or dimming, without abrupt discontinuities. Gradual changes typically reflect sustained socioeconomic or demographic processes such as rural expansion (Fig. 1i), economic transformation or the systematic rollout of new lighting technologies (for example, LED retrofitting). Unlike abrupt events, they result in a smooth and persistent evolution in night-time radiance over time.
Each ALAN change is further classified by its direction (that is, brightening and dimming) based on Extended Data Table 5 (equations (4) and (6)). Brightening corresponds to a positive model-estimated change in radiance, whereas dimming corresponds to a negative change. This directional classification is essential for disentangling the complex global patterns of illumination gain and loss, enabling a more complete understanding of the dynamic behaviour of ALAN across space and time.
Although these persistent changes are the focus of our analysis, transient fluctuations that dissipate within days to a few weeks, such as those caused by temporary outages, meteorological anomalies or daily variations in power supply, are not analysed. These ephemeral changes, which typically return to the original status of the NTL intensity within 1 month, fall outside the analytical scope of this study. Our emphasis is on sustained alterations in ALAN radiance rather than day-to-day variability in the signal. The workflow of our method and analysis is shown in Extended Data Fig. 5.
ALAN change metrics calculation
... continue reading