RADIATIVE FORCING BY GREENHOUSE GASES AND SULFATE AEROSOL

GOALS4.0 ocean-atmospheric coupled model developed by IAP/LASG, was firstly improved, including adding of new greenhouse gases and introducing of the explicit representation of sulfate aerosols. It was then employed to simulate radiative forcing induced by greenhouse gases and sulfate aerosol with 20th century real concentration of greenhouse gases and sulfate aerosol from a sulfur cycle model as input The simulated global and annual mean radiative forcing due to greenhouse gases and sulfate aerosol is 2.17 W/m2 and -0.29 W/m2 respectively, which are within the range of estimates in the latest IPCC report. The forcing from greenhouse gases shows homogeneous spatial distribution, with the maximum of 2.5 W／m2 at the subtropical and the minimum of 1 W/m2 at the polar region, while the forcing by sulfate aerosol almost compete the forcing of greenhouse gases at the major industrial regions in the Northern hemisphere. The zonal nature of radiative forcing due to well mixed greenhouse gases is apparent. The forcing indicates a strong symmetrical structure in the two Hemispheres. Comparing to the forcing due to greenhouse gases, the forcing by sulfate aerosols shows significant regional distribution. Maxima in sulfate are associated with high sulfur emissions in North America, Europe, and Southeast Asia. Secondary maximum in the Southern Hemisphere should be due to biomass burning. Radiative forcing from either greenhouse gases or sulfate aerosols was very low before 1950s, while it increased very fast in the last decades. The forcing due to greenhouse gases and sulfate aerosols was less than 0.6 W/m2 or -0.1 W/m2 in 1950, which increase to about 2.1 W/m2 and -0.5 W/m2 at the end of the 20th century. Considering only greenhouse gases the mean forcing from the two Hemispheres is almost as same as its global mean. By comparison, if the effects of greenhouse gases and sulfate aerosols are both included, the global mean forcing is between the averages of Northern and Southern Hemisphere, and the radiative forcing in the Northern Hemisphere is roughly 3 times as high as that of the Southern Hemisphere.