The stratospheric ozone layer plays an essential role in protecting the Earth’s surface from harmful solar ultraviolet radiation. Recent research on upper stratospheric ozone has started to show significant signs of recovery, while in the lower stratosphere, most research shows ozone is still decreasing. There is some debate in the atmosphere science community about these trends and the quality of existing dataset, which needs to be strong in order to assess long-term stability of the ozone layer. A new study, funded in part by the Climate Program Office’s Atmospheric Chemistry, Carbon Cycle and Climate (AC4) Program, uses atmospheric observations of ozone profiles taken since 1965 to derive long-term trend estimates. An international group of researchers, including AC4-supported scientist Irina Petropavlovskikh of NOAA’s Global Monitoring Laboratory (GML) and the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado, Boulder, filled in gaps and inconsistencies in a global, long-term observational record of atmospheric ozone using linear modeling methods and a continuous measurement series from instruments in Switzerland. The results, published in Atmospheric Chemistry and Physics, support a negative trend of ozone in the lower stratosphere but do not reflect a positive ozone “recovery” in the upper stratosphere, but rather a stagnant trend. More research is needed to replicate and confirm these results. This study improves the quality of global stratospheric ozone data and is part of an ongoing effort by AC4 to explain trends in the existing long-term observational record.