July 13th, 2014
A suite of simulations, done with a new high-resolution climate model (CM2.5) developed at GFDL, were used to study the observed long-term decline of winter rainfall over parts of southern Australia. In response to anthropogenic increases in greenhouse gases and reduction in stratospheric ozone, the model is able to capture many aspects of the observed drying, especially over southwest Australia. The model projects a continued decline in winter rainfall throughout the rest of the 21st century, with significant implications for regional water resources.
In addition to a control simulation, ensembles of simulations were performed that included various combinations of changing radiative forcing, including those from natural sources (volcanic eruptions and solar irradiance changes) and anthropogenic sources (changes in greenhouse gases, aerosols, ozone, and land use changes). The model does not reproduce the observed drying in response to natural forcings, indicating that the observed drying is likely a response to human activity.
Potential future changes in water resources are an immense societal challenge. Improving our ability to simulate observed changes is a vital step towards reliable projections of future changes. This is particularly critical on regional scales, which are most relevant for resource planning and adaptation. This study demonstrates a remarkable advance in NOAA’s capability to simulate observed water resource changes and project future water resource availability on a regional scale.