Editing IPCC:AR6/WGI/Chapter-6 (section)

=== Future Projections for Air Quality Considering Shared Socio-economic Pathways (SSPs) ===

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'''Future air quality (in term of surface ozone and PM concentrations) on global to local scales will be primarily driven by changes in precursor emissions as opposed to climate change''' ( ''high confidence'' ''') and climate change is projected to have mixed effects.''' A warmer climate is expected to reduce surface ozone in regions remote from pollution sources ( ''high confidence'' ) but is expected to increase it by a few parts per billion over polluted regions, depending on ozone precursor levels ( ''medium'' to ''high confidence'' ). Future climate change is expected to have mixed effects, positive or negative, with an overall low effect, on global surface PM and more generally on the aerosol global burden ( ''medium confidence'' ) '','' but stronger effects are not excluded in regions prone to specific meteorological conditions ( ''low confidence'' ). Overall, there is ''low confidence'' in the response of surface ozone and PM to future climate change due to the uncertainty in the response of the natural processes (e.g., stratosphere–troposphere exchange, natural precursor emissions, particularly including biogenic volatile organic compounds, wildfire-emitted precursors, land and marine aerosols, and lightning NO <sub>x</sub> ) to climate change. {6.3, 6.5}

'''The SSPs span a wider range of SLCF emissions than the Representative Concentration Pathways (RCPs), representing better the diversity of future options in air pollution management''' ( ''high confidence'' ''').''' In the SSPs, the socio-economic assumptions and climate change mitigation levels primarily drive future emissions, but the SLCF emissions trajectories are also steered by varying levels of air pollution control originating from the SSP narratives, independently from climate change mitigation. Consequently, SSPs consider a large variety of regional ambitions and effectiveness in implementing air pollution legislation and result in wider range of future air pollution levels and SLCF-induced climate effects. {6.7.1}

'''Air pollution projections range from strong reductions in global surface ozone and PM (e.g.,''' '''SSP1-2.6''' ''', with strong mitigation of both air pollution and climate change) to no improvement and even degradation (e.g.,''' '''SSP3-7.0''' '''without climate change mitigation and with only weak air pollution control)''' ( ''high confidence'' ''').''' Under the SSP3-7.0 scenario, PM levels are projected to increase until 2050 over large parts of Asia, and surface ozone pollution is projected to worsen over all continental areas through 2100 ( ''high confidence'' ). Without climate change mitigation but with stringent air pollution control ( SSP5-8.5 ), PM levels decline through 2100, but high methane levels hamper the decline in global surface ozone at least until 2080 ( ''high confidence'' ). {6.7.1}

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