El Niño-Southern Oscillation (ENSO) describes the cycle of
El Niño, neutral and La Niña patterns in the Pacific
Ocean, which occur on time scales of typically 3-7 years. El Niños
often lead to drier conditions over large parts of Australia, while
La Niñas
tend to enhance rainfall over much of the continent.
Depending on the time of year, El Niño and La Niña can
also affect the:
Further information on El Niño and La Niña is available from the Bureau's Australian Climate Influences web page.
Changes in Australian conditions that result from shifting from one stage of the cycle to the next, or even a longer term continuation of one part of the cycle, (for instance, two La Niña events in a row), raise risks that may require significant changes in farm planning and decision making.
Agricultural planning and decision making is often focused around the current crop or pasture growing season, as well as for periods out to one year. These timescales are exactly those impacted by the extremes of ENSO - La Niña and El Niño - both of which often last for about 10-12 months, and typically have biggest impact in the Australian winter and spring; key times agriculturally.
To manage the risk that El Niño and La Niña present, it is important to monitor the status of ENSO, and furthermore, to be aware that no two El Niño or La Niña episodes, or their impacts upon Australia, are identical.
Recommended actions include:
These actions are, of course, conducted in terms of all other aspects of the farming operation (e.g., price for your commodity, the cost of fuel, debt levels, etc.), and within the long term plan for the farm.
As part of a long term plan and its risk management, it's also worth taking a long term view of ENSO. That is:
It's also becoming increasingly important to understand what may be changing in the background state of the climate, and hence the average climate for your region over which the ENSO impacts apply. This may mean spending a little time, for instance, examining the Bureau of Meteorology/CSIRO 'Climate Change in Australia' report, to become aware of what climate change may mean for your region, and hence factoring that into your ENSO calculations. In other words, will the 'average' years be warmer or drier in the future? Or is your area already undergoing a warming, cooling, drying or wetting trend?
To manage the risk that the extremes of ENSO may raise, it is important to understand how El Niño and La Niña events typically behave once they develop, and to place these typical features in the context of your farming operations.
The following diagram shows a timeline through several seasons of some features associated with a fairly typical El Niño episode and its impact over Australia. In this example, the Southern Oscillation Index (SOI) is used as a measure of how strong the event is. Sustained negative values of the SOI often indicate El Niño episodes while sustained positive values are associated with La Niña. The table beneath the graph shows examples of decision points during the calendar year, relative to the typical El Niño features. The graph illustrates that ongoing monitoring of the climate situation, as described above, can be useful as the agricultural season or year progresses.
Summer | Autumn | Winter | Spring | Summer |
---|---|---|---|---|
Markets and buying considerations General watch on global markets and global climate patterns |
Cultivar choice Stocking rates Mix of activities |
Fertiliser decisions Planning for selling, harvesting, shearing, etc. Fodder needs, haymaking, options for extra plantings, market options |
Soil moisture Check for summer management options |
Similarly the diagram below shows a timeline of some features associated with a fairly typical La Niña episode. It is worth noting that La Niña is not the mirror image or precise opposite of El Niño, neither in its timing during the calendar year nor the geographic extent of its impact on Australia.
It is important to gain insight into the typical effects that La Niña and El Niño events may have for your location; it may well be that the influence is either not as strong, or conversely, even stronger than you think.
For more detailed explanation of the ENSO patterns, see the Australian Climate Influences page, and the maps of the impact upon Australian rainfall of past El Niño and La Niña events.
There may also be other factors that affect your location that need to be considered, such the Indian Ocean, or the current state of the Madden Julian Oscillation. Managing the risk that ENSO provides is best started with understanding how important ENSO is for your region, and similarly, what other weather and climate factors need to be considered if an event is in progress. For instance, in 2007 a La Niña event looked highly likely but as it was developing, cool temperatures in the Indian Ocean formed suddenly during winter; the opposite of what typically occurs. This event appeared to have a negative impact upon rainfall over much of Australia, despite occurring during a period of La Niña formation. Knowing that the Indian Ocean sea surface temperatures impact your location, and being aware that the Indian Ocean effects are included in the Bureau's seasonal climate outlook forecasts, may have helped some users during this unusual event.
Given that El Niño and La Niña:
monitoring the state of the climate can assist with a number of on-farm decisions from the seasonal scale out to about one year.
Typical timelines for El Niño and La Niña episodes
Decisions support tools - some of which are available from the Managing Climate Variability web site - are now commonly used to guide farmers through the seasons. However, even without such tools, a simple decision table can help to clarify the various options related to the climate. An example of how a decision table can be used to explore options for wet, dry or normal seasons is given below. A number of options can be quickly explored in broad terms.
Seasonal decision table for rainfall and exploring particular enterprise options.
Enterprise options |
Rainfall categories |
Under these conditions costs(C) and return (R) could be: |
Net result/profit (P) (rainfall consideration only, excluding other factors) |
Include a realistic range that could be expected |
Check seasonal outlook for most likely rainfall category |
Determine most likely profit range |
---|---|---|---|---|---|---|
Crop x |
Wet range |
C1 |
P1=R1-C1 |
<P1-a to P1+a> |
|
|
R1 |
||||||
Normal range |
P2=R2-C2 |
<P2-b to P2+b> |
Example rainfall range |
<P2-b to P2+b> |
||
C2 |
||||||
R2 |
||||||
Dry range |
C3 |
P3=R3-C3 |
<P3-c to P3+c> |
|
|
|
R3 |
||||||
Notes |
|
|
|
The ranges a,b,c can be based on information about past returns and knowledge of the particular activity |
|
Compare with other enterprise options to help choose enterprise management for the year |
While far from comprehensive, the following list provides an outline of useful questions to ask about your location, and links to information that may help you find the answers, to help understand and manage the climate risks relevant to your farm.
For much of Australia, ENSO, and its extremes of El Niño and La Niña, are the dominant influence upon our climate. To manage the risks they raise it is worthwhile becoming familiar not only with their behaviour, but also with a number of tools that can help once an event is underway.
This page is produced with the support of Managing Climate Variability - a consortium of primary industry research and development corporations.