Fioletov et al. (2017) used Aura Ozone Monitoring Instrument (OMI) satellite measurements of vertical column densities (VCD: the total number of molecules per unit area) of sulfur dioxide, a trace gas, to establish a link between reported sulfur dioxide emissions, OMI sulfur dioxide VCDs measured by satellites, and surface sulfur dioxide concentration measurements. They then estimated annual mean sulfur dioxide VCD distributions (as shown in animation), based on reported point-source emissions for the period 1980–2015, as would have been seen by OMI.