Light Pollution Increased 16% Between 2014 and 2022, Study Finds – PetaPixel

Artificial light pollution increased by 16 percent between 2014 and 2022, according to research highlighting the rapid degradation of the nocturnal environment. This growth in nocturnal luminosity impacts not only the field of astronomy but also biological ecosystems and human circadian rhythms, as the threshold for a truly dark sky becomes increasingly rare.

The findings underscore a global trend where urban expansion and the widespread adoption of inefficient lighting technologies have expanded the reach of light domes—the glow seen over cities from a distance. This data is largely supported by satellite imagery and citizen science initiatives that track the visibility of stars in the night sky.

NASA Satellite Monitoring and the Global Glow

NASA has played a critical role in quantifying this increase through the use of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-satellite System (Suomi NPP). This sensor is designed to detect low-light emissions, allowing researchers to map the intensity of artificial light at night (ALAN) across the entire planet.

The imagery reveals that the brightest regions are concentrated in densely populated urban corridors, particularly in North America, Europe, and East Asia. However, the growth is not limited to existing cities. The data shows a proliferation of light in previously rural or undeveloped areas, indicating that light pollution is encroaching on the last remaining dark-sky preserves.

This expansion is often attributed to the transition to LED lighting. While LEDs are more energy-efficient than high-pressure sodium lamps, many installations utilize a “cool white” spectrum that contains high levels of blue light. Blue light scatters more easily in the atmosphere, which increases the overall skyglow and makes the night sky appear brighter and more washed out.

The Technical Impact on Astronomy and the Bortle Scale

For astronomers and astrophotographers, the increase in light pollution is measured using the Bortle scale. This nine-level numeric scale quantifies the brightness of the night sky, where Class 1 represents a pristine, naturally dark site and Class 9 represents the inner-city sky of a major metropolis.

As the global average of light pollution rises, more regions are shifting upward on the Bortle scale. A location that may have been a Class 3 (Rural Sky) in 2014 may now exhibit characteristics of a Class 4 (Rural/Suburban Transition) or Class 5 (Suburban Sky). This shift obscures faint celestial objects, such as nebulae and distant galaxies, requiring photographers to use more aggressive light-pollution filters or travel further into remote wilderness to achieve high-contrast images.

Beyond ground-based lighting, the tech industry’s push toward low Earth orbit (LEO) satellite constellations has introduced a new variable. Large constellations of communication satellites create visible streaks across long-exposure astronomical photographs. While these are not “light pollution” in the sense of atmospheric glow, they represent a form of orbital interference that complicates the gathering of deep-space data.

Ecological and Human Consequences

The 16 percent increase in light pollution has implications that extend beyond the scientific community. Many nocturnal species rely on the darkness for hunting, mating, and migration. The disruption of these patterns can lead to population declines in insects, birds, and sea turtles.

For humans, the prevalence of artificial light at night disrupts the production of melatonin, the hormone responsible for regulating sleep-wake cycles. The proliferation of high-intensity blue light from streetlights and digital screens contributes to this disruption, which researchers have linked to a variety of health issues, including sleep disorders and metabolic imbalances.

Mitigation and Future Trends

To combat the rise of skyglow, several international organizations are advocating for “dark sky” compliant lighting. This involves three primary technical adjustments:

• Shielding: Ensuring that light fixtures are fully shielded to direct light downward toward the ground rather than allowing it to spill upward or horizontally.
• Color Temperature: Shifting from cool-white LEDs to warm-white or amber LEDs, which emit less blue light and reduce atmospheric scattering.
• Adaptive Lighting: Implementing smart lighting systems that dim or turn off when no pedestrian or vehicular traffic is detected.

As satellite-based monitoring continues to refine the maps of Earth’s nocturnal emissions, the data provides a baseline for regulators to implement lighting ordinances. The goal is to balance the needs of urban safety and infrastructure with the preservation of the natural night sky.