Satellite images show growing darkness in Syria

During the four years that researcher Xi Li has watched Syria's civil war unfold through nighttime satellite imagery, he has seen the pinpricks of light fade to the point where 83 percent of the country's lights have gone out.

"Satellite data never tell lies," said the Chinese-born Li, a visiting scholar at the University of Maryland's Department of Geographic Sciences. "The Syrian people need help."

He has measured the levels of nighttime light across Syria since the conflict began in March 2011. His findings were published last year in the International Journal of Remote Sensing.