Global Sea-level Rise: Past and Future

Detection of Greenhouse-Gas-Induced Climatic Change

“…Transient weakening of the thermohaline circulation slows the global mean surface warming and increases the heat flux into the deep ocean as shown by Wigley and Raper (1987) and, with a 2-D model, by Harvey (1994). In the UD model simulations given in Raper et al (1996b), the upwelling rate is assumed to decline linearly with mixed layer temperature increase until a near-zero value is reached. The mixed layer temperature change at which near zero upwelling is reached is a free parameter in the model, assumed in Raper et al (1996b) to be 7°C based on results from the Hamburg model ECHAMULSG SCENA (Cubasch et al, 1992) experiment (and in broad agreement with the GFDL results).…”

“…In the UD model simulations given in Raper et al (1996b), the upwelling rate is assumed to decline linearly with mixed layer temperature increase until a near-zero value is reached. The mixed layer temperature change at which near zero upwelling is reached is a free parameter in the model, assumed in Raper et al (1996b) to be 7°C based on results from the Hamburg model ECHAMULSG SCENA (Cubasch et al, 1992) experiment (and in broad agreement with the GFDL results). The 7°C value is also fairly consistent with the HADCM2 1% COZ experiment in which the optimum value turns out to be 5.6"C. However, in the HADCM2 GHG and SUL (Mitchell et al, 1995a,b) experiments the decline in the upwelliig rate is much smaller and the appropriate value for this parameter is around 20°C.…”

“…The 7°C value is also fairly consistent with the HADCM2 1% COZ experiment in which the optimum value turns out to be 5.6"C. However, in the HADCM2 GHG and SUL (Mitchell et al, 1995a,b) experiments the decline in the upwelliig rate is much smaller and the appropriate value for this parameter is around 20°C. Thus, the assumed upwellingrate/temperature relationship used in Raper et al (1996b) and by the IPCC (Kattenberg et al, 1996), may not be applicable to all fiture forcing cases. IfUD model and O/AGCM upwelling-rate changes differ, so too will their temperature and expansion results.…”

“…3 .3d). As reported in FY94/95, in Raper et al (1996b) the greater warming over the land was represented in the UD model by using a dfierential land/ocean climate sensitivity (the ratio used was 1.3) (see C5 for derivation). To achieve a good fit to the HADCM2 results a value of the ratio of the land/ocean climate sensitivity of about 1.6 is required.…”

“…In the latter, the appropriate forcing is divided between the fowl and./ocea.n boxes. The two sets of UD model (UDM) results are wifi parameter settings i) as given in Raper et al (1996b) and ii) amended to fit the O/AGCM results (see text).…”