"tendency_of_X" means derivative of X with respect to time. The construction "atmosphere_moles_of_X" means the total number of moles of X in the entire atmosphere, i.e. summed over the atmospheric column and over the entire globe. The chemical formula of CFC113a CCl3CF3. The IUPAC name for CFC113a is 1,1,1-trichloro-2,2,2-trifluoro-ethane.