The Historical and Future Climate Change Impact on the Human Health Burden from Changes in Exposure to Surface Ozone

Kurzfassung

Elevated surface concentrations of ozone can lead to poor air quality and detrimental impacts on human health via respiratory diseases. Concentrations of ozone in the atmosphere are controlled by chemical production and loss, stratosphere-troposphere exchange of ozone, climatic conditions and its removal by deposition at the surface. Here we use the Earth system model, UKESM1, to simulate the change in surface ozone concentrations from different sensitivity scenarios, conducted as part of the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP). We calculate the ozone season daily maximum 8 hour mixing ratio (OSDMA8) to assess the impacts on human health. We find that OSDMA8 values have increased globally from 1850 to 2014 by 40 to 60%, with >90% of the world’s population exposed to values above the WHO air quality guideline value in the present day. In isolation, historical changes in anthropogenic NOx emissions and global CH4 concentrations have increased OSDMA8 values by 32% and 20% respectively, which significantly increases the risk of adverse impacts to human health over certain regions. Historical changes in climate cause small changes in OSDMA8 values, with increases over polluted continental areas (up to 2%) and reductions in more remote regions (up to 3%). Under a high future warming scenario (global mean increase of 5K by 2100) OSDMA8 concentrations increase across polluted continental regions by up to 9% between 2015 and 2100, with reductions of a similar magnitude in remote regions. However, if ozone precursors are also reduced in this future scenario then OSDMA8 values can decrease by ~30% over continental regions, leading to human health benefits. These results show changes in anthropogenic emissions represent the largest risk to human health from long term exposure to surface ozone concentrations, although if future climate change is not mitigated it can also have important regional impacts on concentrations.