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Frequently asked questions about floods, their causes and impacts.
If you live in an area that may be affected by floods it is important to keep up to date with current emergency alerts for your region.
Ensure you are prepared for floods and have access to information via online, radio or television.
For up-to-date weather forecast and flood watch information, see:
For current natural disaster warnings, see:
For information about action to take if a flood is likely, see: Emergency Management Queensland .
Floods are part of Australia’s natural ecology. In 2011, significant floods occurred across southeast Australia, including in the Brisbane catchment causing significant damage.
The Bureau of Meteorology has some great historical information on past Queensland floods, including those that occurred in 1974.
CSIRO scientists advise that recent flood events primarily reflect natural climate variability but that the magnitude of such events over the longer term may increase with climate change.
It’s difficult to determine specifically whether climate change contributed to the current flooding because: each particular extreme event is due to a combination of factors that operate over both short and long periods a wide range of extreme events is a normal occurrence even in a stable climate. However, we expect climate change to alter the likelihood of extreme events such as heatwaves, fires, droughts, and floods.
Modelling studies have indicated that a warming climate is likely to result in increased short-term (24-72 hour) bursts of rainfall in some areas, including parts of South East Queensland. This means that extreme rainfall events are likely to be more intense in the future (mid 21st Century) and so potentially result in more severe flooding.
We know that the world has warmed by about 0.8º C over the past century, and the past decade has been the warmest on record. 2010 was amongst the three warmest years on record, and 2011 was the warmest year with a La Niña event.
The balance of evidence in scientific research shows that it’s very likely that most of the global warming since the mid-20th century is due to increases in greenhouse gases in the atmosphere, primarily as a result of anthropogenic emissions.
We also know that many parts of the world have seen a trend toward more extreme rainfall events since the mid-20th century. It is more likely than not that this trend is due to the increases in atmospheric greenhouse gases.
The extreme rainfall experienced in south-Queensland in 2011 arose from the strongest La Niña event on record.
La Niña events are features of climate variability and reflect year-to-year variations in sea surface temperatures and weather patterns across the Pacific Ocean, commonly referred to as the El Niño – Southern Oscillation or ENSO. The flooding events of 1974 and 2012 also occurred in a strong La Niña period.
The specific contribution of climate change to such individual events is difficult to assess.
Climate change involves long-term changes to the underlying ocean and atmosphere patterns that generate such events as part of year-to-year climate variability.
Warmer oceans and higher sea surface temperatures that result from climate change tend to increase the amount of moisture that gets transported from the ocean to the atmosphere. A warmer atmosphere can hold more moisture and could increase the intensity of extreme rainfall events.
It is expected that long-term climate change will result in greater climate variability with more intense extreme events than in the past.
CSIRO research shows that Australia is likely to become warmer over the coming decades, with a reduction in average annual rainfall in the south-east, and uncertain changes in average annual rainfall in the north, including south-east Queensland.
Climate variability from year to year and within years will be superimposed on these trends in average conditions. For example, a warming trend will include some cool years and many hot years, and a drying trend will include some very wet years and many dry years.
In this highly variable climate, future extreme rainfall events are likely to be more intense resulting in more severe flooding.
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Last updated: Last updated: 22 March 2015
Printed from: FAQs on floods (http://csiroaucd2-cdc.it.csiro.au/en/Research/Environment/Extreme-Events/Floods/FAQs-on-floods)