Sulfur cycle and sulfate radiative forcing simulated from a coupled global climate-chemistry model
Journal
Atmospheric Chemistry and Physics
Journal Volume
10
Journal Issue
8
Pages
3693-3709
Date Issued
2010
Author(s)
Abstract
The sulfur cycle and radiative effects of sulfate aerosol on climate are studied with a Global tropospheric Climate-Chemistry Model in which chemistry, radiation and dynamics are fully coupled. Production and removal mechanisms of sulfate are analyzed for the conditions of natural and anthropogenic sulfur emissions. Results show that the 1985 anthropogenic emission tripled the global SO2 and sulfate loadings from its natural value of 0.16 and 0.10 Tg S, respectively. Under natural conditions, the fraction of sulfate produced in-cloud is 74%; whereas with anthropogenic emissions, the fraction of in-cloud sulfate production slightly increased to 76%. Lifetimes of SO2 and sulfate under polluted conditions are estimated to be 1.7 and 2.0 days, respectively. The tripling of sulfate results in a direct radiative forcing of -0.43 W - -2 (clear-sky) or -0.24 W mminus;-2 (all-sky), and a significant first indirect forcing of -1.85 W m-2, leading to a mean global cooling of about 0.1 K. Regional forcing and responses are significantly stronger than the global values. The first indirect forcing is sensitive to the relationship between aerosol concentration and cloud droplet number concentration which requires further investigation. Two aspects of chemistry-climate interaction are addressed. Firstly, the coupling effects lead to a slight decrease of 1% in global sulfate loading for both the cases of natural and anthropogenic added sulfur emissions. Secondly, only the indirect effect of sulfate aerosols yields significantly stronger signals in changes of near surface temperature and sulfate loading than changes due to intrinsic climate variability, while other responses to the indirect effect and all responses to the direct effect are below noise level. © 2010 Authors(s).
SDGs
Other Subjects
aerosol composition; anthropogenic source; atmospheric plume; atmospheric pollution; computer simulation; concentration (composition); coupling; numerical model; radiative forcing; sulfate; sulfur cycle
Type
journal article