The Wet, Cool Summer in Southeast Australia

Australia: The Land Where Time Began

The Wet, Cool Summer in Southeast Australia – 2010-2011

Key facts:

1. Scientists have said for many years that the surface of the earth is rapidly warming and the climate is changing, and over the last decade the global average temperature has continued to rise. The warmest La Niña on record occurred in 2011which was warmer than all but 1 year on the 20^th century.

2. Intense droughts and flooding rains, the quintessential Australian cycle, is expected to continue into the future. Heavy rainfall events are still expected to occur across the south, with high summer rainfall events expected to continue to be feature of the climate. It is expected that the southern parts of the continent are likely to be drier compared to conditions in the early to mid-20^th century, in the cooler months in particular. Substantial risks to agriculture, water security, natural systems, the economy of Australia and the way of life are posed by these changes.

3. Changes have been observed to have already occurred to when, where and how much rain falls across Australia. Most of eastern and southern Australia has become drier over the last 40 years. Rainfall has been declining in the southwest of the continent, and more recently rainfall has also declined in the southeast, though there have been wet years. Over the last 2 years most of the record rainfall across Australia has fallen during spring and summer. This is in strong contrast to the normal season for rainfall which runs from April to November across the south of the continent. Across southern Australia in 2011 drier than average conditions persisted during the late autumn and early winter period (April to June). This is consistent with drying that has been significant over autumn and winter which has been occurring in the southwest since the 1970s and the southeast since the mid-1990s. It is considered more likely than not that heavy rainfall events will also become more frequent.

4. Steffen et al. say climate change cannot be ruled out as a factor in heavy rainfall events that have occurred recently. The highest recorded sea surface temperatures (SSTs) around northern Australia occurred in the spring and early summer of 2010-2011. There is a very high likelihood that this contributed to the exceptionally high rainfall over much of Australia over the last 2 years. High SSTs in the waters around northern Australia are associated with La Niña events; though warming over the past century has also contributed to the recent record high SSTs.

5. Many regions of Australia are still experiencing drier than average conditions, and recent rains have not made up for the decade of dry conditions. The southeast, southwest, Tasmania and the coast of southeast Queensland show an overall drying trend. The rainfall has remained at very much below average levels in over half of Victoria and about ¾ of Tasmania.

6. In the last 2 years the wetter conditions experienced in southeastern Australia are consistent with what scientists know and understand of how the climate is changing over the long term.

Sources & Further reading