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Signatures of ozone recovery

Signatures of ozone recovery

Climate scientists studying three decades of ozone measurements from seven satellites see a positive trend in the upper stratospheric ozone thanks to international efforts to curb ozone-depleting substances.

The ozone layer protects life on Earth from harmful ultraviolet solar radiation. However, pollutants can break down ozone, thinning this ozone layer and creating the infamous ozone hole. Starting in the 1970s, the stratospheric ozone declined worldwide, with the largest decline of 4 to 8 % per decade seen in the upper stratosphere.

The trend was interrupted following international agreements (Montreal Protocol and its Amendments signed 30 years ago in 1987) on the reduction of ozone-depleting substances, and the first signs of ozone recovery were seen by satellites.

Satellites provide good coverage but operate for a limited number of years. Meanwhile, climate scientists require readings spanning 30 years or more for analysing trends accurately.

The researchers from the Finnish Meteorological Institute participate actively in the European Space Agency Climate Change Initiative, one of the objectives of which is creating long-term ozone datasets for studies of the climate change in the atmosphere.

In a new development, the ozone profile measurements from seven ESA's and NASA's satellite instruments are merged  in a climate data record , which covers  more than 30 years, from 1984 to 2016.

 "By merging the ESA Climate Change Initiative's data with NASA's, we clearly see negative ozone trends in the upper atmosphere before 1997 and positive trends after," concludes Viktoria Sofieva, Senior Research Scientist at the Finnish Meteorological Institute.

"The upper stratospheric trends beyond the tropics are statistically significant and indicate an onset of ozone recovery."

More information:

Senior research scientist Viktoria Sofieva, tel. +358 029 539 4698,

Research Professor  Johanna Tamminen, tel. 040 737 8733,

Research Professor Erkki Kyrölä,   tel. 050 339 7041,

ESA news:

Sofieva, V. F., Kyrölä, E., Laine, M., Tamminen, J., Degenstein, D., Bourassa, A., Roth, C., Zawada, D., Weber, M., Rozanov, A., Rahpoe, N., Stiller, G., Laeng, A., von Clarmann, T., Walker, K. A., Sheese, P., Hubert, D., van Roozendael, M., Zehner, C., Damadeo, R., Zawodny, J., Kramarova, N. and Bhartia, P. K.: Merged SAGE II, Ozone_cci and OMPS ozone profile dataset and evaluation of ozone trends in the stratosphere, Atmos. Chem. Phys., 17(20), 12533–12552, doi:10.5194/acp-17-12533-2017, 2017


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