Volume changes of the Greenland and Antarctic ice sheets have the potential to significantly contribute to global sea-level changes in future warmer climates. The most crucial aspects are how climatic changes will affect the ice sheet's mass balance and how ice dynamics will react to the imposed environmental forcing. This is in addition to the longer-term background trend from adjustments as far back as the last glacial period. Here we focus on model predictions for the 20th and 21st centuries using 3-D thermomechanical ice sheet/ice shelf models driven by climate scenarios obtained from AOGCMs. We scaled high-resolution patterns from the ECHAM4 and HadAM3 time slice integrations with time series from a variety of lower-resolution AOGCM runs to obtain the spread of results for a similar emission scenario. Particular attention is paid to the technique of pattern-scaling and on how GCM based predictions differ from older ice-sheet model results based on more parameterised mass-balance treatments. As a general result, it is found that the effect of increased precipitation on Antarctica clearly dominates over the effect of increased melting on Greenland for the entire range of predictions, implying that both polar ice sheets combined would contribute more negatively to sea-level in the 21st century than often thought. The results are very similar for both time-slice patterns driven by their underlying time evolution series, with most of the scatter in the results provided by the variability in the lower-resolution AOGCMs. These findings will be discussed in the broader framework of current-day model results and of the IPCC TAR sea-level predictions in particular.