EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Tropospheric Ozone Trends in the Arctic

Katharine Law1, Jens Liengaard Hjorth2, Jakob Pernov2,3, Cyndi Whaley4, Henrik Skov2, Martine Collaud Coen5, Joakim Langner6, Stephen Arnold7, and the Arctic tropospheric ozone team*
Katharine Law et al.
  • 1CNRS, LATMOS/IPSL-Sorbonne Université-UVSQ, Paris, France (
  • 2Department of Environmental Science, Interdisciplinary Centre for Climate Change, Aarhus University, Frederiksborgvej 4000, Roskilde, Denmark (,,,
  • 3Extreme Environments Research Laboratory, École Polytechnique Fédérale de Lausanne, 1951 Sion, Switzerland (
  • 4Canadian Centre for Climate modeling and analysis, Environment and Climate Change Canada, Victoria, BC, Canada (,
  • 5Federal Office of Meteorology and Climatology, MeteoSwiss, Payerne, Switzerland (
  • 6Swedish Meteorological and Hydrological Institute, Norrköping, Sweden (
  • 7Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, United Kingdom (
  • *A full list of authors appears at the end of the abstract

Tropospheric ozone, an important air pollutant and short-lived climate forcer, is changing globally with reported increases over emission regions that can influence ozone downwind. Here, ozone trends are examined in the Arctic troposphere, where surface warming is around four times faster than the global mean. Trends at the surface and in the free troposphere are estimated for 1993-2019 using available surface and ozonesonde data. Observed trends are also compared to modelled trends from the Arctic Monitoring Assessment Project (AMAP) multi-model evaluation, where models were run with the same anthropogenic emissions from 1990 to 2015 (Whaley et al., 2022, ACP). Findings include observed increases in annual mean surface ozone at Arctic coastal sites notably driven by increases during winter that are concurrent with decreasing surface carbon monoxide trends. Positive trends are also diagnosed at most high-Arctic ozonesonde sites in the wintertime free troposphere (up to 400 hPa). These ozone increases, which tend to be overestimated by the multi-model median (MMM) trends, are likely to be due to reductions in anthropogenic emission of nitrogen oxides at mid-latitudes leading to less ozone titration and influencing northern hemispheric ozone. Springtime increases are also found at the surface in northern coastal Alaska/Greenland but not in the MMMs. Causes are unknown but may be related to changing Arctic sea-ice or weather patterns affecting ozone sources or sinks. In contrast, surface ozone trends in northern Scandinavia are negative during spring, likely a response to decreasing ozone precursor emissions in Europe. MMM trends are also negative but generally overestimated. Springtime trends in the free troposphere also tend to be negative while summer trends are positive. Changes in ozone precursor emissions, the downward stratospheric ozone flux or general circulation may be contributing to these seasonal variations in the trends. The implications of these reported trends and model behaviour are discussed.

Arctic tropospheric ozone team:

David Tarasick8, Jesper Christensen2, Makoto Deushi9, Peter Effertz10,14, Greg Faluvegi11,12, Michael Gauss13, Ulas Im2, Naga Oshima9, Irina Petropavlovskikh10,14, David Plummer4, Kostas Tsigaridis11,12, Svetlana Tsyro13, Sverre Solberg15 and Stephen T. Turnock16,7

How to cite: Law, K., Liengaard Hjorth, J., Pernov, J., Whaley, C., Skov, H., Collaud Coen, M., Langner, J., and Arnold, S. and the Arctic tropospheric ozone team: Tropospheric Ozone Trends in the Arctic, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3552,, 2023.