The regional temperature implications of strong air quality measures

Abstract

<p><strong>Abstract.</strong> Anthropogenic emissions of short-lived climate forcers (SLCFs) affect both air quality and climate. How much regional temperatures are affected by ambitious SLCF emission mitigation policies, is however still uncertain. We investigate the potential temperature implications of stringent air quality policies, by applying matrices of regional temperature responses to new pathways for future anthropogenic emissions of aerosols, methane (CH<sub>4</sub>) and other short-lived gases. These measures have only minor impact on CO<sub>2</sub> emissions. Two main options are explored, one with climate optimal reductions (i.e. constructed to yield a maximum global cooling) and one with maximum technically feasible reductions. The temperature response is calculated for four latitude response bands (90–28° S, 28° S–28° N, 28–60° N, and 60–90° N) by using existing regional temperature change potential (ARTP) values for four emission regions: Europe, East Asia, shipping, and the rest of the world. By 2050, we find that global surface temperature can be reduced by −0.3 ± 0.08 °C with climate-optimal mitigation of SLCFs relative to a baseline scenario, and as much as −0.7 °C in the Arctic. Cutting CH<sub>4</sub> and BC emissions contribute the most. This could offset warming equal to approximately 15 years of current global CO<sub>2</sub> emissions. If SLCFs are mitigated heavily, we find a net warming of about 0.1 °C, but when uncertainties are included a slight cooling is also possible. In the climate optimal scenario, the largest contributions to cooling comes from the energy, domestic, waste, and transportation sectors. In the maximum technically feasible mitigation scenario, emission changes from the sectors industry, energy, and shipping will give warming. Some measures, such as in the sectors agriculture waste burning, domestic, transport, and industry, have outsized impact on the Arctic, especially by cutting BC emissions in winter in areas near the Arctic.</p>