Reducing Planetary Health Risks Through Short-Lived Climate Forcer Mitigation

Global air pollution and climate change are major threats to planetary health. These threats are strongly linked through the short-lived climate forcers (SLCFs); ozone (O-3), aerosols, and methane (CH4). Understanding the impacts of ambitious SLCF mitigation in different source emission sectors on planetary health indicators can help prioritize international air pollution control strategies. A global Earth system model is applied to quantify the impacts of idealized 50% sustained reductions in year 2005 emissions in the eight largest global anthropogenic source sectors on the SLCFs and three indicators of planetary health: global mean surface air temperature change (increment GSAT), avoided PM2.5-related premature mortalities and gross primary productivity (GPP). The model represents fully coupled atmospheric chemistry, aerosols, land ecosystems and climate, and includes dynamic CH4. Avoided global warming is modest, with largest impacts from 50% cuts in domestic (-0.085 K), agriculture (-0.034 K), and waste/landfill (-0.033 K). The 50% cuts in energy, domestic, and agriculture sector emissions offer the largest opportunities to mitigate global PM2.5-related health risk at around 5%-7% each. Such small global impacts underline the challenges ahead in achieving the World Health Organization aspirational goal of a 2/3 reduction in the number of deaths from air pollution by 2030. Uncertainty due to natural climate variability in PM2.5 is an important underplayed dimension in global health risk assessment that can vastly exceed uncertainty due to the concentration-response functions at the large regional scale. Globally, cuts to agriculture and domestic sector emissions are the most attractive targets to achieve climate and health co-benefits through SLCF mitigation. Plain Language Summary Climate mitigation action must be taken immediately on a global scale if we are to stay within the Paris Agreement temperature limit of well below 2 degrees C. In addition to damaging human and global forest health, air pollutants influence global climate change, some cause global warming, and others cause global cooling. Reducing global air pollution can advance multiple United Nations Sustainable Development Goals but the actual environmental impacts of targeted mitigation options are not well understood. When there are many mitigation options to choose from, with limited resources, decisions must be made to prioritise one action over another and ensure win-win solutions for both climate and heath. This study uses an Earth system model to calculate the impacts of deep cuts in air pollutant emissions from different economic sources sectors on global temperature, human health and land ecosystem health.