Nighttime-Lights-Derived Fossil Fuel Carbon Dioxide Emission Maps and Their Limitations

Abstract

Abstract Brightness of nighttime lights has been used as an indicator for spatial disaggregation of CO 2 emission based on an assumed linear relationship between the digital number (DN) values of nighttime light imagery and the amount of CO 2 emissions. However, reliability of the linear relationship of these variables has not been thoroughly examined. In this study we find that the actual overall correlations are exponential rather than linear. More specific analyses showed that the DN values of nighttime light imagery first behaves linearly (from 3 to 50) and then exponentially (from 51 to 63), correlating to the amount of CO 2 emissions. Regardless of the use of a linear or piecewise function, some featured limitations are evident as we developed the methodology. Among significant limitations, CO 2 emissions were not visualized in unlit areas and a lack of variation existed in regions with the same DN values of nighttime light imagery. Lastly CO 2 emissions in urban core areas were grossly under-estimated.