The experiments with the GFDL model used here were performed using the coupled ocean-atmosphere model described in Manabe et al. (1991) and Stouffer et al., (1994) and references therein. The model has interactive clouds and seasonally varying solar insolation. The atmospheric component has nine finite difference (sigma) levels in the vertical. This version of the model was run at a rhomboidal resolution of 15 waves (R15) yielding an equivalent resolution of about 4.5º latitude by 7.5º longitude. The model has global geography consistent with its computational resolution and seasonal (but not diurnal) variation of insolation. The ocean model is based on that of Byan and Lewis with a spacing between gridpoints of 4.5º latitude and 3.7º longitude. It has 12 unevenly spaced levels in the vertical dimension. To reduce model drift, the fluxes of heat and water are adjusted by amounts which vary seasonally and geographically, but do not change from one year to another.
The GFDL-R15 climate change experiment used here follows the IS92a scenario of estimated past and future greenhouse gas forcing for the period 1765-2065 (Haywood et al., 1997), but only the 100-year segment from 1958-2057 was available through the IPCC DDC. The radiative effects of all greenhouse gases is represented in terms of an equivalent CO2 concentration. We acquired the results from this experiment from the IPCC Data Distribution Centre in 1999. The greenhouse gas only change fields used in SCENGEN are calculated as the difference in climate between the 30-year means of years 2011-2040 and 1961-90 in the greenhouse gas only forced simulation. The global warming by 2011-2040, with respect to 1961-90, was 1.7deg C and the increase in global precipitation was 3.5%, yielding a global precipitation sensitivity of 2.1% per degree Celsius warming. The climate sensitivity of the same atmospheric model, coupled to a mixed-layer ocean, was estimated to be 3.7deg C.
Mean monthly precipitation pattern correlation coefficient = 0.62
Haywood,J.M., Stouffer,R.J., Wetherald,R.T., Manabe,S. and Ramaswamy,V. (1997) Transient response of a coupled model to estimated changes in greenhouse gas and sulphate concentrations Geophys. Res. Letts., 24, 1335-1338.
Knutson,T.R., Manabe,S. and Gu,D. (1997) Simulated ENSO in a global coupled ocean-atmosphere model: multidecadal amplitude modulation and CO2 sensitivity J.Climate, 10, 138-161.
Manabe,S., Stouffer,R.J., Spelman,M.J. and Bryan,K. (1991) Transient response of a coupled ocean-atmosphere model to gradual changes of atmospheric CO2. Part I: annual-mean response J. Climate, 4, 785-818
Stouffer,R.J., Manabe,S. and Vinnikov,K.Ya. (1994) Model assessment of the role of natural variability in recent global warming Nature, 367, 634-636.