Some areas stayed largely the same year over year, but many of those regions, including those in Italy, the Netherlands, Spain and the US, were already among the brightest to begin with. Lighting increased throughout South America, Africa and Asia. And the numbers are likely to underestimate the problem because the satellite used doesn't pick up blue light emitted by LEDs, which have been used more and more in the last few years.

"The numbers are truly shocking, given that we know illuminating the nocturnal environment can have widespread ramifications for the environment and human health," University of Exeter researcher Thomas Davies, who wasn't involved with the study, told Gizmodo. And exactly how much it will impact human and environmental health is unclear since nighttime illumination is a fairly new phenomenon. "Artificial light at night is a very new stressor," said Franz Holker, one of the researchers on the project. "The problem is that light has been introduced in places, times and intensities at which it does not naturally occur and [for] many organisms, there is no chance to adapt to this new stressor."

And unless we change how we're lighting our outdoor spaces, this trend will likely continue. "In the near term, it appears that artificial light emission into the environment will continue to increase, further eroding Earth's remaining land area that experiences natural day-night light cycles," said the study.

Image: Carla Schaffer / AAAS