A detail from the earlier image shows the European mean tropospheric nitrogen dioxide (NO₂) vertical column density (VCD) between January 2003 and June 2004, as measured by the SCIAMACHY instrument on ESA's Envisat. The scale is 10¹⁵ molecules/cm^-2. Image produced by S. Beirle, U. Platt and T. Wagner of the University of Heidelberg's Institute for Environmental Physics.

Credits: University of Heidelberg