This chapter is concerned with the interpretations that can be made from atmospheric observations. It reviews some predictions made by atmospheric models and compares certain model results and atmospheric measurements with an emphasis on detecting evidence of significant disagreements. The vertical profiles of nitrous oxide between 0 and about 35 km have been measured by balloon flights at a wide range of latitudes and the concentrations of nitrous oxide between 40 and 60 km have been measured at one latitude by two rocket flights. The solar proton event may be interpreted as a direct demonstration of stratospheric ozone destruction by a long-chain catalytic process. The importance of the solar proton event of August 1972 is that it demonstrated a conspicuous and unambiguous ozone reduction in the middle and upper stratosphere following the sudden, natural introduction of ozone-destroying catalysts at concentrations 100- to 1000-fold less than that of ozone itself.