Multimodel Surface Temperature Responses to Removal of U.S. Sulfur Dioxide Emissions.

Abstract: Three Earth System models are used to derive surface temperature responses to removal of U.S. anthropogenic SO₂ emissions. Using multicentury perturbation runs with and without U.S. anthropogenic SO₂ emissions, the local and remote surface temperature changes are estimated. In spite of a temperature drift in the control and large internal variability, 200 year simulations yield statistically significant regional surface temperature responses to the removal of U.S. SO₂ emissions. Both local and remote surface temperature changes occur in all models, and the patterns of changes are similar between models for northern hemisphere land regions. We find a global average temperature sensitivity to U.S. SO₂ emissions of 0.0055 K per Tg(SO₂) per year with a range of (0.0036, 0.0078). We examine global and regional responses in SO₄ burdens, aerosol optical depths (AODs), and effective radiative forcing (ERF). While changes in AOD and ERF are concentrated near the source region (United States), the temperature response is spread over the northern hemisphere with amplification of the temperature increase toward the Arctic. In all models, we find a significant response of dust concentrations, which affects the AOD but has no obvious effect on surface temperature. Temperature sensitivity to the ERF of U.S. SO₂ emissions is found to differ from the models' sensitivity to radiative forcing of doubled CO₂. [ABSTRACT FROM AUTHOR]