Nighttime Map Shows the Dramatic Changing of Earth’s Lights

We’ve all seen pictures of the Earth from space, whether in a astronaut film or in our science textbooks in school, we all have a certain image in our minds of how the Earth looks from up above. When night falls on various parts of the Earth, from above, we can also see the amount of light that shines from each country, and according to cartographer John Nelson, the amount of light coming from the Earth has drastically changed in the past few years.

See the examples in the slideshow above.

According to National Geographic, after NASA released a global mosaic of the Earth’s night lights, Nelson, with the help of the mapping-software company Esri, decided to make a map showing a comparison of how light shining from Earth has changed since NASA’s last study in 2012. Through Nelson’s map, we are able to see where the Earth has dimmed, and where it has brightened.

Nelson calculated the difference of brightness of 2016 from 2012, and the places that have dimmed are in blue, while locations that are brighter are in magenta. He talked about the process in making this map in his blog.

“[NASA’s] announcement provided a few before/after swipe images highlighting a handful of interesting places. It was unreasonably fun for me to swipe back and forth, looking for changes,” he said. “Since I am always on the lookout for ways that will reduce the load on my already-taxed cognitive capabilities, I wondered if I might outsource some of that mental effort of looking for change via one of ArcGIS Pro’s raster functions.”

To create these images, Nelson downloaded the eight high-res Earth At Night images produced by NASA, and while using ArcGIS Pro, he combined the maps together with the ‘Raster Functions’ he minimized the pixels from one photo from the other, and made the color differences blue and magenta to present the differences in a more transparent way.

In his images, there are some significant, surprising differences compared to the last study in 2012. Various continents have become darker in the last five years, as well as individual countries. For example, North Korea, at night, is completely dark compared to neighboring South Korea, which is almost completely lit up. According to both maps, there has been little change to the country’s light since 2012. This may have to do with the political regime and climate North Koreans are currently facing. In Europe, there are areas and major cities that have significantly dimmed in the last five years.

“I was very interested to see the suburban growth rings around existing cities,” Nelson said. “Because this map shows the change in the night lights, cities that were already bright in 2012, but grew in 2016, show up as a ring of new light.” This can be seen in countries like India, where the population of people continues to grow.

Nelson said it is important for those outside of the science community to continue looking at data such as this.

“I try to crunch it down into ways that make sense to me, or show something interesting and new. This map potentially shows all sorts of things to folks closer to the underlying causes,” he said. “For example, northern India explodes with new light. Some areas that show reduced light have been impacted by difficult economic conditions or war. And some places have actively tried to reduce their light pollution so that the stars are more visible at night.”

Maps allow viewers to see significant changes on our planet that we may not be able to see unless we are on the outside looking in. These maps show how we as humans have affected the planet, whether through mass industrialization, pollution, overpopulation, and so on. Nelson said it’s important we see and understand these changes.

“Maps are the best; they reveal so much about a phenomenon that you just can’t see from a table or a chart. What’s more, they help you ask better questions, or ask questions you would never have thought of otherwise. I work for Esri, a company that helps people make their own maps so I feel terrifically lucky to not only do what I love, but help others do it too.”

[Images by John Nelson/via Esri]