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 has shifted from North America and Europe to Asia.  This rapid shift, coupled with limited ozone monitoring in developing nations, 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 emissions 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?  To answer these questions the International Global Atmospheric Chemistry Project (IGAC) initiated the Tropospheric Ozone Assessment Report (TOAR).  TOAR’s mission is 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.