Map showing the distribution of eight different chemicals in slices of the Earth's atmosphere. These are surface concentrations from the period of 22nd July to 2nd October 2018. These chemicals react in the presence of sunlight to produce ground level ozone. While ozone in the stratosphere protects us from the Sun's ultraviolet radiation, lower down in the atmosphere it is a harmful pollutant. Data produced by the GEOS modeling system with atmospheric chemistry.