Understand how more intense heat waves in the future could affect severe surface ozone events.
Analyze a global Earth system model that simulates the observed relationship between heat waves and elevated surface ozone levels with associated severe health impacts.
--The model is driven by emissions of greenhouse gases and ozone precursors from a medium-high emission scenario (RCP6.0) compared to an experiment with ozone precursor emissions fixed at 2005 levels.
Ozone concentrations during future more intense heat waves decrease in areas where ozone precursors are prescribed to decrease in RCP6.0 (e.g. most of North America and Europe), and ozone concentrations during heat waves increase in areas where ozone precursors either increase or have little change (e.g. central Asia, the Mideast, northern Africa). With stabilized ozone precursors, surface ozone concentrations increase during future heat waves compared to non-heat wave days in most regions except where there is ozone suppression that is likely associated with changes in isoprene emissions at high temperatures from forests.
This study identifies the relationship between ozone and temperature during heat waves globally and illustrates that temperature is not necessarily a primary control on modeled ozone concentrations in future heat waves. This is due to the dependence on how ozone precursors are prescribed in future emission scenarios, and how related emissions of VOCs can be affected by temperature and influence ozone concentrations. Because of these factors, heat waves in a future warmer climate cannot necessarily be associated with a particular air quality outcome and future emissions of ozone precursors, together with the possibility of effects from ozone suppression at high temperatures will have a role in the ultimate outcome.