Tropospheric Ozone Assessment Report, Phase II (TOAR-II, 2020-2024)

Latest News:

TOAR-II Online Workshop 30 Oct, 2-3 Nov., 2023

TOAR-II database user forum was held 26 September 

Copernicus TOAR-II Community Special Issue is now open for submissions!

Please check the TOAR-II Community Special Issue Guidelines before submitting publications and review the TOAR-II Recommendations for Statistical Analyses

The first hybrid TOAR-II Workshop was held in Cologne, Germany, 8-10 March, 2023. See the Workshop Notes here.

TOAR-II Data User Workshops were held on 

  • 23 June, 2022 12 h CEST to 24 June 15 h CEST 2022 (in-person, Juelich, Germany)
  • 12 July, 2022 05 - 10 UTC   (virtual)
  • 13 July, 2022 13 - 18 UTC   (virtual)
  • 17 and 19 January, 2023 (virtual) 

Recordings from Juelich workshop are available here. 


As of February 2020, TOAR (Tropospheric Ozone Assessment Report: Global metrics for climate change, human health and crop/ecosystem research) has entered its second phase (TOAR-II), the first phase having been completed in 2019. The TOAR mission continues, with TOAR-II providing updated and extended information on tropospheric ozone.

Specifically, the goals of TOAR-II are:

  1. TOAR Ozone Data Portal:  Update the ozone observations in the TOAR surface ozone database to include all recent observations (since 2014), and include data from new sites and regions, as well as ozone precursor and meteorological data.  Develop methods for including historical data (pre-1975) and create working links to repositories of free tropospheric observations.
  2. TOAR publications:  Exploit the new observational datasets collected by Goal 1 (with data through 2020) to provide an updated state of the science estimate of ozone’s global distribution and trends relevant to climate, human health and vegetation.  Extend the statistical toolbox and metrics of the TOAR trend analyses.  These results will be published in the open-access, peer-reviewed literature.
  3. Involve scientists from the atmospheric sciences community, as well as statisticians and scientists who focus on broader issues of global change and sustainability, to identify outstanding science questions in relation to tropospheric ozone.  The range of topics can be expanded beyond the scope of the original TOAR effort to investigate the impacts of tropospheric ozone on climate, human health and vegetation, and to address urban-scale issues in addition to the regional and global scale.
  4. Maximize exploitation of the TOAR Surface Ozone Database by, 1) helping scientists around the world, beyond the TOAR effort, to apply the database to new analyses, and 2) exploring new data science methods to improve the analysis of global ozone trends and their attribution.


To join the TOAR-II email list, sign-up here


Get Involved

The TOAR-II Kick-Off Workshop was held in virtual format over four days in late January and early February 2021.  TOAR-II Kick-Off was the first TOAR-II workshop, designed to gather the community and develop the working groups that will produce the papers for the TOAR-II Community Special Issue (the first step of the second Tropospheric Ozone Assessment Report), as well as identify new datasets for the assessment of tropospheric ozone and its impact on climate, health and vegetation.

Details of the workshop are available in a summary pdf, and additional workshop materials (including all presentations) are available on the TOAR-Repository.  To get involved, please follow the respective links in the summary pdf.

Further information about TOAR-II can be found in the presentation slides from the on-line Quickstart Event held on September 16, 2020:

· Archived recording of the Quickstart Event (link to video)

· Overview of TOAR-I achievements and goals of TOAR-II (pdf)

· TOAR-II data infrastructure: general information (pdf) and recordings from the Data Gathering Event, January 2022

·  How to develop a TOAR-II Working Group (pdf)


Current Working Groups

Chemical Reanalysis Focus Working Group

East Asia Focus Working Group

Global and Regional Models Focus Working Group

HEGIFTOM Focus Working Group

Human Health Impacts of Ozone Focus Working Group

Machine Learning for Tropospheric Ozone

Ozone Deposition Focus Working Group

Ozone over the Oceans Focus Working Group

Ozone and Precursors in the Tropics (OPT) Focus Working Group

Radiative Forcing Focus Working Group

ROSTEES Focus Working Group

Satellite Ozone Focus Working Group

South Asia Focus Working Group

Statistics Focus Working Group

Tropospheric Ozone Precursors (TOP) Focus Working Group

Urban Ozone Focus Working Group


Coordination Teams

TOAR-Climate Coordination Team

TOAR-Health Coordination Team

TOAR-Vegetation Coordination Team



Governance and Procedural Documents

TOAR-II Steering Committee Terms of Reference

TOAR-II Scope and Roadmap for Working Groups and Publications

TOAR-II Guidelines for Working Groups

TOAR-II Working Group application procedure

TOAR-II Guidelines for TCO and profile intercomparisons

TOAR-II Community Special Issue Guidelines

TOAR-II Recommendations for Statistical Analyses