Why do you think that tropospheric NO2 concentrations have changed, based on the video Tale of 3 cities

The answer is atmosphere. there are four spheres of the earth: 1. geosphere (from greek word 'geo' = ground), 2. hydrosphere (from greek word 'hydro' = water), 3. biosphere (from greek word 'bio' = life), and 4. atmosphere (from greek word 'atmo' = air). a magnetosphere is a region of space around astronomical objects controlled by the magnetic field of that object. through the process of elimination, since lightning is present in the air, it can be found in the atmosphere.

  like australopithecus afarensis; probably the direct ancestor of this group. africa: 5.8 to 4.4 million years ago.