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

Latest News:

TOAR-II Kick-Off Workshop

25 January - 3 February, 2021
Held globally in virtual format


What:  The second phase of the Tropospheric Ozone Assessment Report (TOAR-II) was announced during the TOAR-II Quickstart Event on September 16, 2020 (see the event summary below).  We are now inviting the research community to attend a workshop with four 2-hour online sessions in early 2021 to develop the science questions and analyses that will form the foundation of the assessment report.  This will be an interactive event with several breakout sessions and feedback opportunities. Your engagement is needed to shape the next global tropospheric ozone assessment.


  • Monday, January 25, 13:00-15:00 UTC
  • Wednesday, January 27, 13:00-15:00 UTC
  • Thursday, January 28, 13:00-15:00 UTC
  • Wednesday, February 3, 13:00-14:30 UTC

Where:  Held globally in virtual format.      
Agenda:  Coming soon…

Register Now


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


A citable presentation on TOAR-II can be downloaded here


Get Involved

On September 16, 2020, TOAR-II held an on-line Quickstart Event to reach out to the global research community and to ask the members to develop the next assessment report.  To get involved, please see the Quickstart presentations posted below, and archived on the TOAR Data Repository:

Archived recording of the Quickstart Event (link to video)

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

The new TOAR-II data infrastructure (pdf)

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


Current Working Groups

HEGIFTOM Focus Working Group

Oceania Focus Working Group

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

Satellite Ozone Focus Working Group


Procedural Documents

TOAR-II Scope and Roadmap for Working Groups and Publications

TOAR-II Guidelines for Working Groups

TOAR-II Working Group application procedure


Upcoming Events

TOAR-II Kick-Off Workshop
IGAC Sponsored
Everywhere in virtual format

Past Events

TOAR-II Quickstart Virtual Event
IGAC Sponsored

Register for the Event Here, TOAR II Website
Workshop on Ozone in the Lower Atmosphere in Oceania: First Regional Workshop of the Tropospheric Ozone Assessment Report phase II (TOAR-II) (Postponed to Sep or Oct 2020)
IGAC Sponsored
Aspendale, Victoria, Australia

Workshop Announcement815.14 KB