Frequently asked questions

What are the characteristics of the current climate of south-eastern Australia?


The climate of the SEACI study region is highly variable with large differences in temperature, rainfall and evaporation from one year to the next and has, historically, been subject to both extreme floods and droughts. It spans several different climates: cool; humid eastern uplands; temperate southeast mallee; inland subtropical northern areas; and hot, dry arid and semi arid country in the far west.

South-eastern Australia’s climate is influenced by large-scale features of the atmospheric circulation. These include:

How is the climate of south-eastern Australia changing?

Across south-eastern Australia over the past thirteen years, there has been an apparent shift to a warmer and drier climate, which has had major impacts on our water resources.

The temperature of south-eastern Australia (as over most of Australia) has been rising in recent decades. The warmest year since 1910 was 2007 and every year since 1996 has been warmer than the 1961–1990 mean.

The 13-year period from 1997 to 2009 has been the driest since 1900 with only 515 mm average annual rainfall across the SEACI region compared with a long-term historical mean of 581 mm. The rainfall in south-eastern Australia has been below the long-term mean every year since 1997, except in 1999 and 2000 (when the anomalies were only 13 mm and 28 mm respectively).

What is the difference between climate change and variability?

'Climate variability' refers to shorter term (daily, seasonal, annual, inter-annual and/or several years) variations in climate, including the fluctuations associated with El Niño (dry) or La Niña (wet) events.

'Climate change' refers to long-term (decades or longer) trends in climate averages such as the global warming that has been observed over the past century, and long-term changes in variability (e.g. in the frequency, severity and duration of extreme events).

The South Eastern Australian Climate Initiative will help us understand the extent to which recent climatic changes can be attributed to various causal factors, including the enhanced greenhouse effect.

What have been the characteristics of the current dry period?

SEACI research shows that the dry spell experienced from 1997 to 2009 represents the driest 13-year period in the last 110 years of reliable climate records. Not only has it lasted longer than any previously recorded dry period, it has also been characterised by a lack of wet years. Further, 11 of the past 13 years have been below the long-term mean. The major decrease in rainfall in the region was experienced in the autumn months, rather than in winter or spring.

The current drought has been largely confined to southern Australia, rather than extending over most of the continent.

What has been the effect of the recent drought on rainfall and runoff in south-eastern Australia?


A 13 per cent reduction in rainfall was observed over the southern Murray-Darling Basin from 1997–2006, which has led to an extreme and unprecedented decline in runoff of 44 per cent. The cause for this amplified decline in runoff is:

What are the implications for south-eastern Australia, and particularly the southern Murray-Darling Basin, if projected changes to rainfall and runoff come about?

Most climate change models predict that sub-tropical areas in the world, including the south-east of Australia, are entering a significant drying period. There are firm signals that the current long-term drought correlates with future projections of changes to climate and reduced rainfall in the south-east of Australia.

There are major implications for southern food-producing regions in Australia that depend on reliable water resources, with declines in rainfall and runoff likely to affect rivers and dam storages. In the southern Murray-Darling Basin, for instance, there is likely to be less water available in the future, leading to an increased focus on improvements in water-use efficiency to maintain production levels.

The decline in rainfall and runoff is also likely to impact on water supply for cities and towns. The Basin Plan for the integrated and sustainable management of water resources will assist communities who depend on these resources to adapt to a changing climate.

Is the current dry period attributable to climate change or variability?

While there is evidence that the current drought is at least partly caused by climate change, scientists are yet to determine in percentage terms how much is caused by this phenomena compared to natural climate variability. This question will be a focus point of investigation for Phase 2 of SEACI.

The SEACI research program has made significant advances in identifying the drivers of a changing climate and the current drought in the south-east. It has found that increasing global temperatures are likely to be changing large-scale weather patterns and contributing to reduced rainfall and runoff. Natural climate variability is also likely to be a factor, but the degree in which both are contributing to the drought is yet to be fully understood.

The scientific evidence for the impact of climate change on the south-east is linked to the very low autumn rainfall and low winter and spring rainfall which is associated with changes in large-scale global circulation patterns. The sub-tropical ridge (STR), a high pressure system that sits over the south-east, is one such factor. SEACI research has found that there is a strong relationship between rising intensification of the STR and declines in rainfall over the region. Using climate models, SEACI scientists have shown that the intensification of the STR can only be achieved when greenhouse gases are factored into to their models.

How does SEACI relate to other research programs?

SEACI builds on the existing knowledge available from many other climate programs, both in Australia and internationally. Advances made through SEACI research will enhance capacity within the Australian science community investigating climate change and climate variability, just as advances in climate science through other programs will benefit SEACI.

SEACI has been designed to answer the questions that are most critical to natural resource managers in south eastern Australia. The Indian Ocean Climate Initiative (IOCI) is a program of research in Western Australia that has been running since 1998. Like SEACI, IOCI is aimed at better understanding both climate variability and climate change.

Other research initiatives with relevance to SEACI include the Eastern Seaboard Climate Change Initiative, the Centre for Australia Weather and Climate Research, and the National Climate Centre.

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