Saturday March 31st at 8:30pm local time everywhere will mark Earth Hour. For one hour, millions will switch off their lights as a way to come together to demonstrate the need to take action on climate change. Why at night? The increase of energy consumption worldwide can be visualized through the comparison of night light maps.
In the animated GIF below, the image of Europe at night taken in 1992 and in 2010, shows a strong increase in the use of lights in urbanized areas and along roads. The images were acquired by the United States’ Defense Meteorological Satellites Program (DMSP) Operational Linescan System (OLS), run by the National Oceanic and Atmospheric Administration (the nighttime lights data series can be downloaded from DMSP download page). The satellites monitor the meteorological, oceanographic and solar–terrestrial physics environments for the US Department of Defense. NASA’s Bright Lights, Big City is using these composite satellite images to understand the growth of urbanization worldwide.
The night light maps can also be used to identify anomalies. Such as the darkness that makes up the country of North Korea as compared to its neighboring countries on the night light map.
Blue Marble Generator has a Google Maps overlay using the 2010 OLS night light imagery.
Not all night time lights are from urban light sources. This amazing map from shows all the night time light sources of the world in 2003 using the same OLS sourced data. The map was created by National Geophysical Data Center. These include a blaze of red lights across Africa from fires, gas flares (green) in parts of Russia, and boat lights (blue) off the coast of South Africa and Japan.