| Abstract: | Two sensitivity experiments, in which CO2 is instantaneously doubled, have been performed with a general circulation model to determine the influence of the convective parametrization on simulated climate change. We have examined the spatial structure of changes in the annual mean and annual cycle for surface temperature and precipitation for both experiments; similarly we have examined changes in the variance for these two fields. We have also computed a range of test statistics in order to obtain reliable measures of the signal-to-noise ratio in the climate change signal from each experiment. We have computed test statistics for the entire globe and for five different region and we contrast the global response with the response in the Australian region taken as a representative sample.We find that the highest signal-to-noise ratios in the change from 1 * CO2 to 2 * CO2 are for the change in surface temperature for both experiments with little difference in the global averages between the experiments. Globally averaged precipitation shows a greater noise level but perhaps the greatest contrast between experiments. There are generally significant increases in the temporal and spatial variability of precipitation in the change from the 1 * CO2 to 2 * CO2 and with some differences apparent between the two experiments. The temporal variability of surface temperature does not change significantly in any of the 2 * CO2 cases, and there is little difference between the experiments. There is a significant decrease in the spatial variability of surface temperature in all 2 * CO2 experiments in all cases and with significant differences in the seasonal variations between different experiments. The spatial variability of precipitation increases in all 2 * CO2 cases and also with substantial differences in the seasonal variations between the experiments. There are accompanying significantly different spatial pattern correlations for both surface temperature and precipitation. In general we find that the global changes are fairly robust with the differences associated with convective parametrization schemes being very small. However, at the regional level, there are marked differences between experiments with changes both in the means and in the spatial and temporal variances but often with low levels of significance. |
