Tropospheric Ozone Assessment Report (TOAR)

Global metrics for climate change, human health and crop/ecosystem research

Owen Cooper, NOAA Earth System Research Laboratory/University of Colorado

Steering Committee Members

Mat Evans, University of York, UK
Allen Lefohn, A.S.L & Associates, Helena, Montana, USA
Martin Schultz, Forschungszentrum Jülich, Germany
David Tarasick, Air Quality Research Division, Environment Canada, Downsview, Canada
Anne Thompson, NASA Goddard Space Flight Center, Greenbelt, USA
Aijun Ding, Institute for Climate and Global Change Research, Nanjing University, Nanjing, China
Zhaozhong Feng, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
Manish Naja, Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India
Elena Paoletti, Institute for Sustainable Plant Protection, National Research Council, Florence, Italy
Ian Galbally, CSIRO Marine and Atmospheric Research, Aspendale, Australia

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).

TOAR Assessment: Open Comment Period
TOAR is now available for open comments from February 15 through June 1, 2017, with the papers posted to the website as they become available. Please visit the Open Comments webpage for additional information.

Recent Workshops
TOAR Workshop 1.04
25-29 April 2016
Jülich, Germany
Workshop Summary (Full Version)

TOAR Workshop 1.03
25-27 January 2016
Beijing, China
Workshop Summary (Full Version)

TOAR Workshop 1.02
(hosted by Spanish Met Service, AEMET)
28-30 April 2015
Madrid, Spain
Workshop Summary (Full Version)
IGACnews Workshop Summary

TOAR Workshop I.01
(hosted by NOAA/ESRL/CSD)
10-11 December 2014
Boulder, CO USA
Workshop Summary (Full Version)
IGACnews Workshop Summary

Relevant Publications
Overview of TOAR (Updated February 2017)
TOAR List of Metrics (Updated June 2016)