Changes in light patterns during Christmas in the United States and the Muslim holy month of Ramadan in the Middle East are visible from space.
In an analysis of light output from 70 cities during 2012 and 2013, researchers found that light intensity increased 30 to 50 percent during the Christmas season in most suburbs and major city outskirts. Central urban areas were 20 to 30 percent brighter.
The researchers observed similar trends in Middle Eastern cities during the holy month of Ramadan, when people tend to push back social gatherings and meals until after daytime fasting. Those observations, however, varied from place to place depending on cultural and social dynamics of communities.
“The peaks that we observed are really ubiquitous and occur during the holidays,” says Eleanor Stokes, a PhD candidate at the Yale School of Forestry and Environmental Studies and a NASA Jenkins Graduate Fellow. “[But] in the Middle East, we found a lot of variation between cities, with these lighting patterns tracking cultural variations.”
Vary by Neighborhood
In some locations, including the Saudi Arabian cities of Riyadh and Jeddah, light usage increased by as much as 100 percent throughout the month. But in other regions there was little or no increase.
In Cairo, the variations could be seen even at the neighborhood level, which corresponded with cultural or socioeconomic trends.
For instance, in wealthier and more liberal districts, they found that light usage increased throughout the month. But in poorer, and more devout, neighborhoods, people tended to observe Ramadan without significant increases in light use until the Eid al-Fitr celebration that marks the end of the holiday.
“We saw that, at least during these short-term patterns, energy use is very connected to the cultural and social contexts in which someone lives,” Stokes says.
The data was collected by an instrument aboard the NOAA/NASA National Polar-orbiting Partnership (Suomi NPP) satellite capable of detecting the glow of cities and towns worldwide. Using an advanced algorithm developed by NASA’s Goddard Space Flight Center, researchers were able to filter out moonlight, clouds, and airborne particles.
The co-leader of the research was Miguel Román, a research physical scientist at NASA Goddard and member of the Suomi NPP Land Discipline Team.
The findings provide critical insights into how broad societal forces impact energy decisions, Stokes says. And with the UN Intergovernmental Panel on Climate Change (IPCC) suggesting that energy efficiency and conservation will play a key role in reducing greenhouse gas emissions, these insights have become increasingly important, she adds.
NASA and the National Oceanic and Atmospheric Administration (NOAA) supported the project.