Nighttime Illumination Continues to Grow Worldwide

Excessive artificial nighttime lighting can negatively affect human health and disturb ecosystems.  A new study used remotely sensed data from an earth observation satellite to analyze the rate of increase in artificial night lights between 2012 and 2016. The used data from the Visible Infrared Imaging Radiometer Suite Day-Night Band (VIIRS DNB) via the the Suomi National Polar-orbiting Partnership (NPP) satellite.  The DNB uses a sensing technique designed to capture low-light emissions (More: New map of the world’s night lights).  The improved spatial resolution of near 750 meters allows for the study of night time lighting at the neighborhood level.

Changes in Artificial Lighting From 2012 to 2016

The study found that nighttime artificial lighting between 2012 to 2016  grew by 2.2% per year, with a total radiance growth of 1.8% per year. The rate of increase varied between countries.  Countries experiencing conflict, such as Yemen and Syria, had a net decrease in nighttime lighting.  Some of the brightest lit countries (Italy, Netherlands, Spain, and the United States) show a stabilization in night lighting.  South America, Africa, and Asia exhibit a growth in nighttime illumination during the study period.  Accurate results for Australia were impacted by the presence of wildfires.

Geographic patterns in changes in artificial lighting.

Geographic patterns in changes in artificial lighting. Map: Kyba et al., 2017.

Changes in Lighting Technology

The study found that some large cities showed a decreased in light intensity in their cores but an increased in the surrounding suburban areas.  One example described by the authors is the city of Milan, Italy.  This was less the result of a reduced light source but a change from yellow/orange (sodium vapor) to white (LED) lighting in the city core.  This in turn resulted in a lower radiance measurement due to the sensor’s lack of sensitivity to light sources in the 400 to 500 nm range.

Change in lighting technology in Milan, Italy, observed from space.

Change in lighting technology in Milan, Italy, observed from space.

 

The Study

Kyba, C. C., Kuester, T., de Miguel, A. S., Baugh, K., Jechow, A., Hölker, F., … & Guanter, L. (2017). Artificially lit surface of Earth at night increasing in radiance and extent. Science advances, 3(11), e1701528.

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