In this paper we briefly describe the characteristics and the performance of our 1-D Muenster Climate Model. The model system consists of coupled models including gas cycle models, an energy balance model and a sea level rise model. The chemical feedback mechanisms among greenhouse gases are not included. This model, which is a scientifically-based parameterized simulation model, is used here primarily to help assess the effectiveness of various plausible policy options in mitigating the additional man-made greenhouse warming and the resulting sea level rise. For setting priorities it is important to assess the effectiveness of the various measures by which the greenhouse effect can be reduced. To this end we take a Scenario Business-as-Usual as a reference case (Leggett et al., 1992) and study the mitigating effects of the following four packages of measures: The Copenhagen Agreements on CFC, HCFC, and halon reduction (GECR, 1992), the Tropical Forest Preservation Plan of the Climate Enquete-Commission of the German Parliament on CO, reduction (ECGP, 1990), a detailed reduction scheme for energy-related CO2 (ECGP, 1990), and a preliminary scheme for CH4, CO, and N2O reduction (Bach and Jain, 1992-1993). The required reduction depends, among others, on the desired climate and ecosystem protection. This is defined by the Enquete-Commission and others as a mean global rate of surface temperature change of ca. 0.1-degrees-C per decade - assumed to be critical to many ecosystems - and a mean global warming ceiling of ca. 2-degrees-C in 2100 relative to 1860. Our results show that the Copenhagen Agreements, the Tropical Forest Preservation Plan, the energy-related CO2 reduction scheme, and the CH, and N2O reduction schemes could mitigate the anthropogenic greenhouse warming by ca. 12%, 6%, 35%, and 9% respectively. Taken together, all four packages of measures could reduce the man-made greenhouse effect by more than 60% until 2100; i.e. over the climate sensitivity range 2.5-degrees-C (1.5 to 4.5) for 2 x CO2, the warming could be reduced from 3.5-degrees-C (2.4 to 5.0) without specific measures to 1.3-degrees-C (0.9 to 2.0) with the above packages of measures; and likewise, the mean global sea level rise could be reduced from 65 cm (46 to 88) without specific measures to 32 cm (22 to 47) with the above measures. Finally, the model results also emphasize the importance of trace gases other than CO2 in mitigating additional man-made greenhouse warming. According to our preliminary estimates, CH4 could in the short term make a sizable contribution to the reduction of the greenhouse effect (because of its relatively short lifetime of 10 yr), as could N2O in the medium and long term (with a relatively long lifetime of 150 yr).
