Abstract
Abstract. Short-lived anthropogenic climate forcers (SLCFs), such as sulfate aerosols, affect both climate and air quality. Despite being short-lived, these forcers do not affect temperatures only locally; regions far away from the emission sources are also affected. Climate metrics are often used in a policy context to compare the climate impact of different anthropogenic forcing agents. These metrics typically relate a forcing change in a certain region with a temperature change in another region and thus often require a separate model to convert emission changes to radiative forcing (RF) changes. In this study, we used a coupled Earth system model, NorESM (Norwegian Earth System Model), to calculate emission-to-temperature-response metrics for sulfur dioxide (SO2) emission changes in four different policy-relevant regions: Europe (EU), North America (NA), East Asia (EA) and South Asia (SA). We first increased the SO2 emissions in each individual region by an amount giving approximately the same global average radiative forcing change (−0.45 Wm−2). The global mean temperature change per unit sulfur emission compared to the control experiment was independent of emission region and equal to ∼0.006 K(TgSyr−1)−1. On a regional scale, the Arctic showed the largest temperature response in all experiments. The second largest temperature change occurred in the region of the imposed emission increase, except when South Asian emissions were changed; in this experiment, the temperature response was approximately the same in South Asia and East Asia. We also examined the non-linearity of the temperature response by removing all anthropogenic SO2 emissions over Europe in one experiment. In this case, the temperature response (both global and regional) was twice that in the corresponding experiment with a European emission increase. This non-linearity in the temperature response is one of many uncertainties associated with the use of simplified climate metrics.
Highlights
Anthropogenic emissions of short-lived climate forcers (SLCFs), i.e. chemical components in the atmosphere that interact with radiation, have both an immediate effect on local air quality and regional and global effects on the climate in terms of changes in the temperature and precipitation distribution
All emission changes are located in the Northern Hemisphere, and atmospheric transport of aerosol particles will contribute to a redistribution of atmospheric concentrations and the resulting column burden and radiative forcing of the aerosol, so that in some cases the resulting column burden and radiative forcing from emission changes in different regions will partly overlap
Four experiments were performed where emissions were increased relative to the year 2000 in each individual region to yield similar global mean radiative forcing values
Summary
Anthropogenic emissions of short-lived climate forcers (SLCFs), i.e. chemical components in the atmosphere that interact with radiation, have both an immediate effect on local air quality and regional and global effects on the climate in terms of changes in the temperature and precipitation distribution. The short atmospheric residence times of SLCFs such as sulfate and carbonaceous aerosols (around days) lead to high atmospheric concentrations in emission regions and a highly variable radiative forcing (RF) pattern. We investigate the effect of sulfate aerosol precursor emission perturbations in different regions. A. Lewinschal et al.: Local and remote temperature response of regional SO2 emissions on the global surface temperature distribution using a global climate model
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