Our nights have been getting 2 percent lighter every year

Our nights have been getting 2...
The lights of Earth as they appeared from space, in 2012
The lights of Earth as they appeared from space, in 2012
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The lights of Earth as they appeared from space, in 2012
The lights of Earth as they appeared from space, in 2012

If you're thinking that it seems a little less dark at night these days … well, you might not be imagining things. According to a new study led by Dr. Christopher Kyba of the German Research Center for Geoscience, Earth's artificially lit outdoor areas grew in size and radiance by 2.2 percent per year – on average – from 2012 to 2016.

For the study, Kyba and his team analyzed data gathered by the space-based Visible Infrared Imaging Radiometer (VIIRS), comparing annual readings for different geographical regions over the four-year period. The VIIRS is installed on the NOAA (National Oceanic and Atmospheric Administration) satellite Suomi-NPP, and is the first such device designed specifically for imaging night-time lights.

Although the overall trend was definitely upward, changes in lighting intensity varied a lot by country, with developing nations leading the way. Particularly bright places like the US and Spain remained relatively stable over the four years, for instance, with larger increases occurring in most nations within South America, Africa and Asia.

Globally, it was found that increases in lighting corresponded closely to increases in the Gross Domestic Product. Lighting radiance decreased in only a few countries, such as Yemen and Syria, which are both in the midst of wars.

It should be noted that the VIIRS doesn't detect light at wavelengths below 500 nanometers. This "blue" light can be seen by people, and makes up a significant portion of the light given off by LED streetlights. Essentially, this means that as cities have replaced older orange streetlights with more efficient LED models, the radiometer may have detected a decrease in visible light that didn't really happen – at least, not as far as the human eye is concerned.

A paper on the research was recently published in the journal Science Advances.

Source: German Research Center for Geoscience via EurekAlert

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1 comment
Outdoor lighting at night is an arms race. Super bright lights at night limit your ability to see anything else. LED's may be efficient but "warm" (red spectrum) lighting is essential at night because it's softer and doesn't ruin your night vision as much. In residential neighborhoods warmer red/yellow spectrum lighting should essentially be the requirement as they are far more pleasant and make for less light pollution. Having walked around some neighborhoods at night that use proper lighting I have no idea why anyone would mandate the ~6000K temperature lights my town decided would be a good idea. If I look directly down at the pavement they are OK but as long as the actual lamp is within my peripheral vision (which is most the time) it's blinding and unpleasant. Most people who work for towns are too busy with other things to do a research paper on lighting color temperatures and I lack a decent resource on the subject to direct anyone to. I saw a dark sky astronomy group with a website on the subject but all the content on that subject was missing or had broken links. Society tends to go with the status quo on everything until someone in silicon valley gets funding to challenge it.