New maps from NASA using nearly a decade’s worth of data show how the use of artificial light has shifted over the years.
To make the maps, NASA researchers analyzed data collected by its “Black Marble” program, which uses a specialized sensor to capture low-light imagery of Earth at night. The data was collected by three different satellites between 2014 and 2022.
Researchers expected to find “a gradual increase in artificial light at night” over the years, NASA said in a news release. What they discovered was “much more nuanced patterns” of light radiance.
“The analysis portrays a world flickering with industrial booms and busts, construction, and blackouts, as well as more gradual shifts, such as policy-driven retrofits,” NASA said.
NASA Earth Observatory/Michael Garrison 
The researchers found that each location examined by the sensors underwent several distinct shifts over the nine years data was collected. During that time, radiance increased 34%, while dimming offset it by 18%, the researchers said. Both lighting and dimming “markedly intensified over the past decade,” the researchers said in a study published in the academic journal Nature.
“This evidence of increasing volatility in human night-time activity provides an important dynamic dimension for understanding urban evolution, energy transitions, policy impacts and ecological consequences of rapidly changing illuminated nights,” the researchers wrote.
In the United States, West Coast cities grew brighter as populations increased. On the East Coast, there was more dimming, which the researchers attributed to the use of energy-efficient lightbulbs and “broader economic restructuring.”
NASA Earth Observatory/Michael Garrison 
Worldwide, nights grew brighter in China and northern India, as urban development expanded. Throughout Europe, there was a pattern of dimming likely caused by energy conservation measures, and a sharp drop-off in 2022 after the war in Ukraine led to a regional energy crisis.
“This global, high-resolution analysis … refines and expands our understanding of how humanity is altering the night environment,” the researchers wrote in their published paper. “Our findings show that the human light footprint is not a universally expanding entity but a dynamic system, characterized by the pervasive coexistence of brightening and dimming.”