Testing for changes in light emissions from certified International Dark Sky Places

Abstract

The International Dark-Sky Places (IDSP) program of the International Dark-Sky Association is a voluntary certification in which communities commit via legislative changes to move towards more sustainable lighting that reduces light pollution. As over 115 IDSP have now been certified, it is interesting to ask the extent to which this certification results in reduced light emissions. In this paper, we compared trends in upward light emission of 98 communities located in or near IDSP to those of 98 similarly sized communities further away from the IDSP, using a night lights observing satellite (the Visible Infrared Imaging Radiometer Suite Day-Night Band). The current dataset is not sufficient to distinguish the hypothesis that IDSP certification results in a lower rate of change in upward light emissions from the null hypothesis that IDSP certification has no impact. This result is with regard to upward light emissions only: it is possible that certification has resulted in decreases in night sky brightness that the satellite is not able to observe.