For anyone who has ever joked that a house aglow with festive lights could be seen from space, US space agency NASA now has the data to back you up.
Researchers analysing daily data from the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite have identified changing patterns in night-time light intensity during major holidays such as Christmas and New Year in the US and Ramadan in the Middle East.
According to the satellite data, night-time lights shine 20 to 50pc brighter during Christmas and New Year in many major US cities while, in some Midle Eastern cities, an increase of more than 50pc is observed during Ramadan.
Suomi NPP is a joint NASA and National Oceanic and Atmospheric Administration (NOAA) mission, and the data comes from an instrument called the Visible Infrared Imaging Radiometer Suite (VIIRS), which can detect the glowing lights of towns and cities from the dark side of the Earth under nightfall.
NASA-NOAA Suomi NPP satellite data shows how city lights shine brighter during the holidays in US cities. Dark green pixels are areas where lights are 50pc brighter or more during December. Image by Jesse Allen/NASA’s Earth Observatory/Flickr
This latest analysis used an advanced algorithm developed at NASA’s Goddard Space Flight Center to filter out moonlight, clouds and airborne particles in order to isolate the light from man-made sources. This high-quality satellite information could then paint a picture of light output across the globe, showing scientists when and how brightly the night was illuminated.
The increases were first spotted when a large discrepancy was discovered in data from Egypt’s capital city, Cairo, in 2012. This either meant that there was something wrong with the data or there was something to look into.
NASA-NOAA Suomi NPP satellite data shows how city lights brighten in Cairo during Ramadan. Dark green pixels are areas where the lights are 50pc brighter or more. Image by Jesse Allen/NASA’s Earth Observatory/Flickr
It was then observed that the large increase in light output corresponded with the holy month of Ramadan, during which Muslims fast during the day and eat only after the sun sets.
Three consecutive years of data analysis showed a pattern of increases that followed the Islamic calendar even as Ramadan shifted to earlier in the year. In some Saudi Arabian cities such as Riyadh and Jeddah, light output even increased from 60 to 100pc during Ramadan.
The high-resolution imaging provided by VIIRS also enabled researchers to see variations of light output across different neighbourhoods in Cairo.
NASA-NOAA Suomi NPP satellite data from Saudi Arabia, showing light output increases in Jeddah and Riyadh. Image by Jesse Allen/NASA’s Earth Observatory/Flickr
The researchers also examined the light output across 70 US cities in 2012 and 2013. In these cities, an increase in night-time light output is observed from Black Friday, the day after Thanksgiving, and continues until New Year’s Day.
NASA-NOAA Suomi NPP satellite data from the US states Texas and Louisiana, showing light output increases during December. Image by Jesse Allen/NASA’s Earth Observatory/Flickr
This data can not only be used to prove to your neighbour that yes, indeed, you can see their Christmas lights from space, but more importantly it’s a first step in determining patterns in urban energy use, which is a key factor in measuring greenhouse gas emissions.
“More than 70pc of greenhouse gas emissions come from urban areas,” said NASA Goddard research physical scientist Miguel Román, a lead researcher on this team.
“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 centres, and socio-cultural settings affect energy-use decisions.”
The results of this study were presented at the American Geophysical Union’s Fall Meeting in San Francisco this week.
Main image of decorated house by romakoma via Shutterstock