The image above shows the monotonic trend in nighttime lights from 1992-2008. The data series is produced from the Operational Linescan System (OLS) sensor of the United States Defense Meteorological Satellite Program (DMSP). This sensor is very sensitive to light and has been used to create annual images of stable lights. The analysis was conducted using the Earth Trends Modeler by Ananya Baruah and Annalise Erkkinen -- two graduate students at Clark University. Trend monotonicity measures the degree to which data values are consistently increasing (red) or decreasing (blue). More extreme values indicate greater consistency in the trend. Areas that appear white are not necessarily dark. It simply means that the light levels are unchanging. Thus the central cores of Paris and London both appear white in this image.
What is remarkable about this image is the clear evidence of political boundaries. The increases in nighttime lights in Poland are extraordinary and are consistent with the fact that Poland's GDP increased over 500% from 1992 to 2008. However, an explanation based on the economy doesn't always work. For example, the UK and France experienced similar economic growth over this period, but opposite trends in the nighttime lights.
Do you have any insights on the trends evident in this image? If so, please leave a comment. Thanks