Climate change and long term water availability in Western Australia - An experimental projection

The population of the Perth-Bunbury region in Western Australia is predicted to increase to3.1 million by 2050. Water supply is a key issue, as below-average rainfall since the mid-1970s has led to about40% decline in the streamflow. General Circulation Models (GCMs) project a further decrease in rainfall leadingto diminished water resources in the future and posing a threat to water supply and the environment. In thisexperimental study we assess the impact of climate change at Serpentine Reservoir using data from elevenGCMs which contributed to the latest Intergovernmental Panel on Climate Change (IPCC) assessment report.Data from two emission scenarios (A2 and B1) were used and downscaled, using a state-of-the-art statisticaldownscaling model, to a 5 km resolution compatible with catchment modelling. The LUCICAT rainfall-runoffmodel was calibrated for the Serpentine catchment and then changes in runoff were projected using thedownscaled rainfall data. Land use and potential evaporation were not changed for the future rainfall-runoffmodelling. Nearly all GCMs projected reductions in rainfall by mid (2046-2065) and late (2081-2100) 21stcentury compared to 1981-2000 period. There was a significant variation in projected rainfall reductionsbetween different GCMs and emission scenarios. Under the A2 climate scenario, there could be a further 14-24% reduction in rainfall, and this would result in a 49-69% reduction in reservoir inflow by the mid to end ofthe 21st century. Rainfall reduction under B1 scenario would be around 12% and corresponded to streamflowreduction of about 45-46%

Climate change and long term water availability in Western Australia - An experimental projection

The population of the Perth-Bunbury region in Western Australia is predicted to increase to3.1 million by 2050. Water supply is a key issue, as below-average rainfall since the mid-1970s has led to about40% decline in the streamflow. General Circulation Models (GCMs) project a further decrease in rainfall leadingto diminished water resources in the future and posing a threat to water supply and the environment. In thisexperimental study we assess the impact of climate change at Serpentine Reservoir using data from elevenGCMs which contributed to the latest Intergovernmental Panel on Climate Change (IPCC) assessment report.Data from two emission scenarios (A2 and B1) were used and downscaled, using a state-of-the-art statisticaldownscaling model, to a 5 km resolution compatible with catchment modelling. The LUCICAT rainfall-runoffmodel was calibrated for the Serpentine catchment and then changes in runoff were projected using thedownscaled rainfall data. Land use and potential evaporation were not changed for the future rainfall-runoffmodelling. Nearly all GCMs projected reductions in rainfall by mid (2046-2065) and late (2081-2100) 21stcentury compared to 1981-2000 period. There was a significant variation in projected rainfall reductionsbetween different GCMs and emission scenarios. Under the A2 climate scenario, there could be a further 14-24% reduction in rainfall, and this would result in a 49-69% reduction in reservoir inflow by the mid to end ofthe 21st century. Rainfall reduction under B1 scenario would be around 12% and corresponded to streamflowreduction of about 45-46%

Cloud feedback in atmospheric general circulation models: An update

Six years ago, we compared the climate sensitivity of 19 atmospheric general circulation models and found a roughly threefold variation among the models; most of this variation was attributed to differences in the models' depictions of cloud feedback. In an update of this comparison, current models showed considerably smaller differences in net cloud feedback, with most producing modest values. There are, however, substantial differences in the feedback components, indicating that the models still have physical disagreements