ozone vs troposphere

ozone

noun
  • Hypernym: greenhouse gas 

  • An allotrope of oxygen (symbol O₃) having three atoms in the molecule instead of the usual two; it is a toxic gas, generated from oxygen by electrical discharge. 

  • Fresh air, especially that breathed at the seaside and smelling of seaweed. 

verb
  • To treat with ozone. 

troposphere

noun
  • The lower levels of the atmosphere extending from the surface of the Earth or another celestial body up to the tropopause. It is characterized by convective air movements and a large vertical temperature change. 

How often have the words ozone and troposphere occurred in a corpus of books? (source: Google Ngram Viewer )