Tropospheric Ozone Assessment Report (TOAR)

TOAR Assessment Report:  Papers published so far
The assessment report is being published as a series of papers in the peer-reviewed journal, Elementa – Science of the Anthropocene.   Papers published so far are available through a Special Feature of Elementa:

  • Schultz et al. (2017): Tropospheric Ozone Assessment Report: Database and metrics data of global surface ozone observations, doi: 10.1525/elementa.244
  • Chang et al. (2017): Regional trend analysis of surface ozone observations from monitoring networks in eastern North America, Europe and East Asia, doi: 10.1525/elementa.243

TOAR Database of Surface Ozone Metrics
TOAR has produced a relational database of global surface ozone observations, and generated a comprehensive suite of ozone metrics products including standard statistics, health and vegetation impact metrics, and trend information.  The metrics are made available through a common data portal and a web interface as described by Schultz et al. (2017) in the TOAR Special Feature described above.  Pre-compiled surface ozone metrics data sets can be downloaded from PANGAEA.

TOAR Database

Open Comment Period
Prior to peer-review all TOAR papers will be available for a 30-day Open Comment period, with the papers posted to this website as they become available. Please visit the Open Comments webpage for additional information.

Tropospheric ozone is a greenhouse gas and pollutant detrimental to human health and crop and ecosystem productivity. Since 1990 a large portion of the anthropogenic emissions that react in the atmosphere to produce ozone have shifted from North America and Europe to Asia. This rapid shift, coupled with limited ozone monitoring in developing nations, has left scientists unable to answer the most basic questions: Which regions of the world have the greatest human and plant exposure to ozone pollution? Is ozone continuing to decline in nations with strong emission controls? To what extent is ozone increasing in the developing world? How can the atmospheric sciences community facilitate access to the ozone metrics necessary for quantifying ozone’s impact on human health and crop/ecosystem productivity? TOAR is designed to answer these questions through the development of an assessment report based on expert opinion and analysis, and the generation of a range of ozone metrics at hundreds of sites around the world.

To provide the research community with an up-to-date scientific assessment of tropospheric ozone’s global distribution and trends from the surface to the tropopause.


  1. Produce the first tropospheric ozone assessment report based on the peer-reviewed literature and new analyses.
  2. Generate easily accessible, documented data on ozone exposure and dose metrics at hundreds of measurement sites around the world (urban and non-urban), freely accessible for research on the global-scale impact of ozone on climate, human health and crop/ecosystem productivity.

TOAR is a science effort initiated by IGAC, and developed by an international team of experts. TOAR receives financial and logistical support from IGAC, the US National Oceanic and Atmospheric Administration, and The World Meteorological Organization (an agency of the United Nations).

Recent Events

TOAR Workshop 1.04
IGAC Sponsored
Jülich, Germany
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TOAR Workshop 1.03
IGAC Sponsored
Beijing, China
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TOAR Workshop 1.02
IGAC Sponsored
Madrid, Spain
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TOAR Workshop 1.01
IGAC Sponsored
Boulder, CO, USA
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