Research into how variations in atmospheric and ocean variations contribute significantly to droughts and floods such as those recently experienced across south-east Australia and Queensland has been presented at a workshop hosted by the South Eastern Australian Climate Initiative (SEACI),  a three-year, $9 million research program investigating the causes and impacts of climate variability and change throughout south-eastern Australia.


SEACI Program Director Dr David Post said there is growing evidence from SEACI research that a long-term trend towards a drier climate is taking place.


"“We now also have a better understanding of the drivers behind these variations in rainfall, as measured by things such as: the El Nino-Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), the Southern Annual Mode (SAM) and the sub-tropical ridge (STR). We also have some understanding of how the drivers of rainfall interact to produce extreme climatic events such as the Millennium Drought and 2010/11 floods. The next step is to determine to what extent some of the changes are linked to global warming, and to figure out how these conditions may change into the future in a warmer world."


SEACI research has already determined a relationship between rainfall in south-eastern Australia and the intensity of the STR. The STR is the belt of high-pressure systems around the mid-latitudes.  It is the surface signature of the Hadley Cell, which is the process by which heat is transported from equatorial zones to mid-latitudes. There are changes in the Hadley Cell, and therefore the STR, associated with global warming, with the STR intensifying with increasing global surface temperature.


“However, there are other climatic relationships which are not yet known. For example, while it appears that the IOD and SAM may trend more positive with increasing global temperatures, it is not clear how ENSO will respond to increasing global temperatures, ,” Dr Post said


SEACI is a partnership between the CSIRO Water for a Healthy Country Flagship, the Bureau of Meteorology, the Murray–Darling Basin Authority, the Victorian Department of Sustainability and Environment, and the Australian Government's Department of Climate Change and Energy Efficiency.