2009 NOAA study National Oceanic and Atmospheric Administration N2O attacks ozone National Oceanic and Atmospheric Administration 2009 NOAA study National Oceanic and Atmospheric Administration nitrogen oxides Študija NOAA, August 27, 2009 National Oceanic and Atmospheric Administration National Oceanic and Atmospheric Administration summary of the study on the NOAA website 2009 NOAA study National Oceanic and Atmospheric Administration Študija NOAA, August 27, 2009