Measurements of HCl and HF above Arizona from 1970 to 2012
  We have observed at high resolution spectroscopic changes in Hydrogen Chloride (HCl) and Hydrogen Fluoride (HF) atmospheric trace gases from the 1970s through 2012. HCl rose in strength through 1998 and then decreased to 2012. HF has shown a continual increase to date. Both results are in general agreement with observations from the Jungfraujoch in the Swiss alps. 
Lloyd Wallace and William Livingston
physics.ao-ph