Across the world during the holiday season, whether suburban Phoenix or Riyadh, Saudi Arabia, many people take great pride in adorning their homes and businesses with decorative lights: strings of blinking bulbs, glowing plastic Santas, and riding sleighs, or illuminated crescent moons and five-pointed stars.
For the first time, NASA satellite imagery reveals the difference in the amount of light generated in major cities around the world during the holidays, compared to other times of year.
It's official — our holiday lights are so bright we can see them from space. (Video by NASA's Goddard Space Flight Center)
A team of NASA scientists co-led by Miguel Román examined the light output in major cities in the United States and the Middle East. In the US, nighttime lights, they found, shine 20 percent to 50 percent brighter during the holidays, compared with other times of the year.
"It's a near ubiquitous signal. Despite being ethnically and religiously diverse, we found that the US experiences a holiday increase that is present across most urban communities," Román said. "These lighting patterns are tracking a national shared tradition."
In most suburban areas of the United States, light intensity increased by 30 percent to 50 percent, while in urban areas the increase ranged from 20 percent to 30 percent.
"Overall, we see less light increases in the dense urban centers, compared to the suburbs and small towns where you have more yard space and single-family homes," said Eleanor Stokes, a NASA science fellow and PhD candidate at Yale University's School of Forestry and Environmental Studies, who co-led the study.
Lights in the Middle East during Ramadan are 50 percent brighter, compared to other months. And, in some Saudi cities, like Riyadh and Jeddah, the increase was as much as 100 percent during the Islamic holy month. Light intensity increased only slightly, however, in Turkey. In some areas of Iraq, Syria, and Lebanon output even decreased, possibly due to electricity grid failure or conflict, the scientists said.
"Even within majority Muslim populations, there are a lot of variations," said Stokes. "What we've seen is that these lighting patterns track cultural variation within the Middle East."
The Suomi National Polar-orbiting Partnership satellite, a joint-mission by NASA and the National Oceanic and Atmospheric Administration, generated the images. An instrument called the Visible Infrared Imaging Radiometer Suite is deployed on the satellite and can detect the glow of lights in cities and towns worldwide.
The images help scientists determine energy consumption patterns and where increased energy use is concentrated around the United States and the world. It's an important piece of the puzzle in figuring out how to reduce emissions of heat-trapping gases, like carbon dioxide, which is causing climate change.
"More than 70 percent of greenhouse gas emissions come from urban areas," Román said. "If we're going to reduce these emissions, then we'll have to do more than just use energy-efficient cars and appliances. We also need to understand how dominant social phenomena, the changing demographics of urban centers, and socio-cultural settings affect energy-use decisions."
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