The role of ozone and water vapour in our atmosphere
Ozone and water vapour play fundamental roles in the Earth’s atmosphere and are deeply involved in several major environmental concerns: air quality, climate change and ultraviolet radiation. Ozone in the troposphere causes respiratory problems, reduces ecosystem productivity and acts as a greenhouse gas. Ozone in the stratosphere, on the other hand, protects life at the surface from harmful solar UV radiation, it determines the thermal structure and radiative balance in the stratosphere, and affects surface temperatures as well. Water vapour is the single most important natural greenhouse gas in the atmosphere and provides a strong positive feedback to anthropogenic climate forcing from carbon dioxide; its tropospheric abundance determines cloud formation and the water cycle.
Understanding long-term changes in concentrations
Changes in the distribution and cycles of ozone and water vapour are indicators of changes in their precursors, in global atmospheric transport, in the exchange between troposphere and stratosphere, and in the link between atmospheric composition and climate. Therefore, it is of particular scientific, political and societal importance to be able to quantify and understand changes in tropospheric and stratospheric abundance of these two constituents, at different temporal and spatial scales, and to discriminate their anthropogenic causes from natural processes.
Confidence of past scientific assessments
Several international initiatives and projects, supported by e.g. IGAC (International Global Atmospheric Chemistry project), SPARC (Stratosphere troposphere Processes And their Role in Climate) and WMO’s Global Atmospheric Watch (GAW), have been launched to improve the observational constraints on the present-day distribution, its interannual variability and long-term changes of ozone and water vapour. Despite these efforts, the latest international scientific assessments (TOAR-I, 2019; IPCC, 2021; WMO/UNEP, 2022) conclude that the level of confidence in long-term trends of stratospheric water vapour (low), lower stratospheric ozone (medium) and tropospheric ozone (medium) is below par. Also currently lacking is a view on horizontal patterns in climate variability and long-term trends of stratospheric ozone and water vapour.
The TAPIOWCA project
The TAPIOWCA project (for long-Term Assessment, Proxies and Indicators of Ozone and Water vapour changes affecting Climate and Air quality) aims to tackle several technical challenges in the integrated use and analysis of multiple ozone and water vapour satellite data records. We will then apply the extended time series analysis techniques to the harmonised satellite data records and reassess the present-day mean state, the climate variability and long-term trend in water vapour and ozone across the troposphere and stratosphere. The research objectives for TAPIOWCA are listed on this page.