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Regional Mapping for Climate Change

The overall aim of this project is to update the South Coast NRM regional strategy, Southern Prospects 2011-2016, so it incorporates climate change science information and scenarios that plan for climate change impacts.

As the regional strategy is not due to be updated until 2017 an Addendum has been completed.

Supporting the Addendum is a Geographical Information System (GIS) using maps to demonstrate where priority biodiversity and revegetation activities could occur in the South Coast.        

Information generated from the project will guide the decision-making process as to what type of biodiversity and revegetation activities are needed and at what location, optimising the environmental, water and agricultural outcomes of Carbon Farming Initiative projects.

Project Overview

Project Overview

Regional NRM Planning for Climate Change is funded by the Australian Government under stream 1 of the NRM Planning for Climate Change Fund. By February 2016, 53 NRM organisations across Australia will undertake projects to update existing regional NRM plans.

Stream 1 has $28.9 million available over four financial years to support NRM organisations revise existing regional NRM plans to help identify where in the landscape adaptation and mitigation activities should be undertaken.

This stream is being administered by the Department of Sustainability, Environment, Water, Population and Communities (DSEWPaC).

Support will come from stream 2 of the same fund which has $15 million available over four financial years to produce regional level climate change information and provide guidance on the integration of that information into regional NRM and land use planning.

This stream is being administered by the Department of Industry, Innovation, Climate Change, Science, Research and Tertiary Education (DIICCSRTE).

The University of Western Australia’s Centre for Excellence in Natural Resource Management is supporting the project, by completing regional bioclimatic modelling of key flora and fauna species in the South Coast region to assess the impact of a changing climate on our biodiversity. 

More information can be found at:

Impacts of a Changing Climate

The impact of climate change on South Coast communities dependent on water, agricultural systems and biodiversity will be significant.

Climate change is likely to exacerbate the stress on ecosystems already under pressure from habitat loss, fragmentation, invasive species and changed fire regimes.

During a 2014 risk assessment and adaption workshop, almost 100 climate change risks were identified and rated, while 50 adaption policies and measures were identified in the report  - Climate change:  Whole of Landscape Analysis of the Impacts and Options for the South Coast Region.

Impacts from climate change include warmer, drier conditions across much of the region with increased risk of severe weather events such as storms, flooding, heatwaves, drought and bush fires.

The south-west of WA has witnessed a significant decrease in rainfall since the 1970s with projections for a further drying of the climate. Annual average temperatures are predicted to increase by approximately 1°C over southern WA by 2030.

Climate models predict significant differences in the extent of the reduction and changes in the timing of rainfall from west to east and north to south. 

Click the links for further information. summarising the state of the climate series data, trends


The Addendum is a supporting document to Southern Prospects 2011-2016 and provides a summary of the impacts a changing climate will have on the region’s coastal and marine and water resources, agriculture, cultural heritage and biodiversity.

It also documents the latest climate science and provides a strategic framework to assist planning for climate adaptation and mitigation actions for the region. 

The Addendum also provides guidelines - - to help carbon farming proponents ensure their projects adhere to the regional NRM strategy as required under the Carbon Farming Initiative Act 2011. 

The Addendum is supported by a Geographical Information System (GIS) platform identifying priority landscapes for climate mitigation and adaption actions for improving landscape connectivity, resilience and wildlife corridors, including carbon sequestration opportunities.    

Stakeholder participation

To ensure successful participation in the project, several methods of engagement will be used including:      

  • Workshops with South Coast NRM reference groups and key stakeholders (Local Government Authority members, Aboriginal representatives and State Government agencies) to develop program logic which will be incorporated into the Addendum.       
  • Workshops with technical working groups to develop GIS platform – including decision making framework to support modelling processes. 
  • Community events including Climate Forum and Climate Chaos at the WA Museum (Albany).
  • Climate roadshow targeting Landcare, sub-regional and production groups and Local Government Authorities.
  • Creating a stream 1 working group which meets monthly with all regional NRM group climate change project leaders.
  • Media articles and Facebook updates   
  • Public comment on the draft Addendum and GIS platform. 

Carbon Farming Initiative

The Carbon Farming Initiative (CFI) allows farmers and land managers to earn carbon credits by storing carbon or reducing greenhouse gas emissions on their land, which can then be sold to businesses wishing to offset their emissions.

The CFI also helps the environment by encouraging sustainable farming and providing a source of funding for landscape restoration projects.

The CFI is a legislated offsets scheme. The Carbon Credits (Carbon Farming Initiative) 2011 (CFI Act) was passed by Parliament on August 23, 2011 and received royal assent on September 15, 2011.

Amendments to the CFI regulations came into force on 29 May 2012.

Carbon Farming Guiding Principles

Under the current CFI legislation, carbon farming proponents are required to state their project is consistent with the relevant regional NRM plan.

Therefore, the WA NRM regions (South West Catchment Council, Wheatbelt NRM, Perth NRM, Northern Agricultural Catchment Council and South Coast NRM) involved in the stream 1 NRM Planning for Climate Change Project, formed a working group to ensure cross-regional information was collaborated and to capitalise on project synergies.

A major outcome already produced by the working group is the Carbon Farming Guiding Principles which will be added to the Addendum.

A supporting GIS platform is being developed by South Coast NRM to spatially represent these principles.

Visualising Climate Data

NASA has used weather data culled from more than 1,000 meteorological stations around the world, satellite measurements of sea surface temperature and recordings from an Antarctic research station to produce a short 30 second video to illustrate the rise in global temperatures over the last 130 years.

The visualisation highlights the accelerated warming since the 1970s and more recent peaks, with nine out of 10 of the most recent years being the warmest on record.

If you are interested in Australian climate variability and future projections and would like to see historical trend maps based on real (measured) data visit:

Modelling of climate effects on Australian weather projections can be viewed at

Introduction to Climate Science

The topics of global warming and climate change are often controversial, polarizing and highly politicized and there tends to be very different views in any regional community on the need for action.

It is difficult to convey the complexities of climate change science and it appears that the public finds it hard to accept the scientific uncertainty associated with climate projections.

In many cases, people find it hard to relate to climate change projections as they don’t relate to their personal experience of their local climate and this lack of understanding can result in disengagement or active disagreement.

It is important to convey that climate projections are not forecasts, but projections of plausible future climate scenarios.

The projections are based on models using the best available scientific information at any given time and are given as a range - climate scientists make the uncertainties in the modeling and projections very clear.

“Decisions will need to be made before we have absolute certainty about the future. The role of climate science is to inform these decisions by providing the best possible knowledge of climate outcomes and the consequences of alternative courses of action” (Australian Academy of Science 2010 p16).

Even though there is uncertainty, climate change and increased climate variability are very real natural resource management risks for the South Coast region and have to be managed in an integrated way with other environmental risks.

Uncertainty is not a reason to do nothing. There are also linkages, complex relationships and non-linear feedbacks between socio-economic, ecological and climatic systems.

These interactions need to be considered at landscape level and it will important for South Coast NRM to determine where in the landscape there are particular vulnerabilities as a result of climate change.

The problem is, that with increasing variability in climate and the likelihood of major long-term changes, past climate is much less likely to be a reliable indicator of future climate.

Sudden, stepped changes in rainfall have already occurred in the south-west corner of WA. These rainfall declines are mainly due to large-scale changes in the atmospheric circulation and are thought be from both natural variability and global warming; land use change may also have contributed.

Increases in temperature, which are considered highly likely, will also increase evaporation. The combination of more dry seasons, higher temperatures and increased evaporation will have impacts on biodiversity; agriculture and hydrological systems such as wetlands, waterways and groundwater.

Many of the ecological systems on the South Coast are already under stress and there is a risk that climate change may push them beyond their capacity to adapt.

Climate change is also impacting on Indigenous people’s cultural links with the landscape. Aboriginal people on the South Coast developed natural seasonal calendars based around their interaction with ecological cycles.

Climate change is changing the characteristics of those calendars. Traditionally the Noongar seasons Birak, Bunuru, Djeran, Makuru, Djilba and Kambarang, have guided Aboriginal people on seasonal change. In the report of the Indigenous Peoples’ Global Summit on Climate Change held in 2009, Indigenous participants called for immediate action on climate change including:

“We call upon the parties to the UNFCCC [United Nations Framework Convention on Climate Change] to recognize the importance of our Traditional Knowledge and practices shared by Indigenous peoples in developing strategies to address climate change.”

Greenhouse gases (GHG) and global warming are impacting on the oceans off the South Coast. At present, the oceans absorb approximately one-third of the total amount of greenhouse gases emitted to the atmosphere.

The absorption of carbon leads to acidification of the oceans with the Southern Ocean predicted to reach a tipping point at 450ppm carbon dioxide. Global warming is increasing sea-levels as oceans warm and expand.

The IPCC (2014) has found that as a result of the capacity of the water to absorb heat and the huge mass of the ocean, the oceans have accumulated more than 90 per cent of the surplus heat associated with increasing GHG concentrations since the 1950s.

Melting ice also contributes to rising sea levels. The interaction between ocean temperatures and atmospheric circulation is one of the factors driving climate variability in an extremely complex system.

The Complexity of Climate and Climate Science

The global climate system involves interactions of a whole range of factors such as position of land masses, solar radiation, sea surface temperatures, ocean currents, ice sheets, atmospheric temperature and other factors, such as volcanic activity.  

One of the problems with complex systems like the global climate, is there are non-linear effects - there can be critical thresholds and interactions, which result in rapid shifts and surprises, with sudden and potentially disastrous consequences.

The changes in the climate system, induced by GHG emissions, also interact with unknown natural climate variations, or climate changes due to land use change and this leads to even more uncertainty about future climate.

A number of major climate drivers influence regional scale climate in the South Coast region but local climate is also influenced by changes in the shape of the coastline, ocean currents, topography, vegetation cover and other factors, which can influence climate at a local scale.

There are also seasonal variations with increasing and decreasing periods of rainfall due to natural climate variation.

The region’s climate is highly variable from season to season and this natural variability is governed by some major climate influences, some of which have only recently been described.

Winter rainfall in WA’s south-west is influenced by the upper level jet stream and the fronts, lows and high-pressure systems. Summer rainfall is sporadic and can be associated, particularly in the east of the region with the end of tropical cyclones.

Factors Influencing Climate Variability

Australian Climate Influences

Australian Climate Influences Map

MAP Source: Australian Bureau of Meteorology

The climate influences in Western Australia have been better understood since the advent of the Indian Ocean Climate Initiative. This research initiative was set up in 1998 as a partnership between CSIRO, the Bureau of Meteorology and the Government of Western Australia.

The main influence on the south-west’s climate in recent years has been changes in the upper level jetstream. These changes appear to have decreased the number of storms coming to the region.

The El Niño Southern Oscillation, which when it seesaws, changes conditions between wet and dry in the eastern states, has less effect on WA climate but may interact with other state climate influences.

Climate scientists believe the main seesaw influences on the climate of the south-west of WA are the Southern Annular Mode (SAM) and the Indian Ocean Dipole (IOD).

Southern Annular Mode (SAM)

The Southern Annular Mode (SAM), also known as the Antarctic Oscillation, is a westerly wind belt circling Antarctica. It is labeled negative when it moves north, away from Antarctica and positive (or in high mode) when it moves towards higher latitudes and Antarctica.

In a positive SAM, the westerly wind belt moves south, resulting in weaker westerlies and more high-pressure systems over the south west and South Coast, restricting the penetration of cold fronts and resulting in low autumn and winter rainfall.

Although a positive SAM results in drier conditions on most of the South Coast, it correlates with more rainfall in spring in the eastern part of the region. In a negative SAM, the wind belt moves north, causing more low-pressure systems and more winter storms over the south-west and South Coast.

There is an increasing trend in SAM towards a positive phase, with westerly winds moving further towards Antarctica in summer and autumn months. The westerly winds and associated low- pressure brings rain to the Southern Ocean rather than the South Coast. The climate models show that as GHG rise, there is a trend for SAM to move towards Antarctica.

Indian Ocean Dipole

Changes in sea surface temperatures in the tropical parts of the Indian Ocean influence rainfall in central and southern Australia. The Indian Ocean Dipole (IOD) is generally measured as an index based on sea surface temperatures in the western, compared to the eastern, tropical Indian Ocean.

In a positive IOD, the sea surface temperatures off the Sumatra-Java coast to the north-west of WA tend be cooler than normal and water in the tropical western Indian Ocean is warmer than normal.

These changes cause a decrease in rainfall over parts of central and southern Australia. When the relative sea temperatures reverse, a negative IOD causes an increase in rainfall.  It has been discovered that positive IOD modes have a bigger effect than negative modes, so the influence of a positive IOD on rainfall decline is greater.

When the IOD is in a positive phase at the same time as an El Niño phase, the drying effect is more extreme in Australia. There is still scientific uncertainty about the IOD and its impact and relationship with El Niño phases.

El-Nino Southern Oscillation (ENSO)

The El Niño Southern Oscillation (ENSO) is the oscillation between El Niño (drier) and La Niña (wetter) conditions in Australia. The oscillation is caused by changes in the strengths of the trade winds and hence temperatures in the western, versus the eastern and central Pacific Ocean

The change in the warming pattern causes rain and cloud to move from one side of the Pacific to the other. In the La Niña phase the western Pacific is warmer and brings clouds and rainfall to eastern Australia. In El Niño the rain and cloud move away from Australia.

ENSO is measured as the pressure difference between Tahiti and Darwin. Negative values (below -8) over a period often indicate an oscillation to El Niño.

The Bureau of Meteorology has compared rainfall across Australia for La Niña and El Niño oscillations to try and get a better understanding of how these episodes impact on rainfall anomalies

From this data it appears some areas of the South Coast region have a decline in winter-spring rainfall during El Niño events, while some patchy eastern areas of the South Coast appear to receive a little more summer rainfall. The interpretation may be complicated by inter-relationships between ENSO and the IOD.

A central Pacific sea surface temperature pattern (El Niño-Modoki) appearing to influence winter rainfall in Australia was described in 2007.

Sub-tropical ridge

The sub-tropical ridge runs across a belt of high-pressure systems. It moves south in summer and is associated with dry and stable conditions because of the descending air. In autumn the ridge moves northwards.

South West Australian Circulation

In addition to the large-scale atmospheric circulations there appears to be an independent regional atmospheric circulation over the south-west of WA. There is evidence that the South West Australian Circulation (SWAC) becomes stronger or weaker just as the monsoon does and this appears to govern winter rainfall in the south west. The SWAC has become weaker in recent years and may explain the early winter drying trend but the reason is unclear.

These climate influences on the south-west and their interactions with one another are not completely understood, so there is need for more research. Nevertheless, it is clear the main climate influences are driving a trend to drying and warming. Climate projections based on scenarios of increased greenhouse gas emissions indicate this trend is likely to continue.

The Enhanced Greenhouse Effect

The greenhouse effect describes the process by which certain gases trap the heat in the earth’s atmosphere. This natural process enables the earth to be warm enough for us to live on it. Physical principles make it clear that increasing greenhouse gases will increase the temperature of the planet (Australian Academy of Science, 2010).

The enhanced greenhouse effect is the effect of adding extra greenhouse gases from human activities such as the burning of forests, fossil fuel combustion (coal, oil and natural gas) land clearing and agriculture. Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and chemicals such as chlorofluorocarbons (CFCs)

Global atmospheric concentrations of major greenhouse gases have increased as a result of human activities since the Industrial Revolution began in 1780 and the rate of increase is speeding up. Human activity is rapidly changing the earth’s carbon cycle.

Between 1990 and 2010, fossil fuel carbon dioxide emissions increased by 49 per cent, even after a 1.3 per cent decline in 2009 due to the global financial crisis.

Rapid warming of the planet is causing major changes in the dynamics of the earth’s climate system. Solar radiation and volcanic activity are the two main natural causes of climate forcing but the evidence is extremely strong that the current rate of global warming is not related to either of those causes. Most climate scientists accept that the current rapid global warming is due to greenhouse gas emissions (Australian Academy of Science, 2010).

Evidence for global warming comes from data on increased air and sea temperatures, melting of snow and ice and rises in sea level. Even if greenhouse gases were stabilised at some time in the future, climate change would continue for a long time and the climate may not return to its original conditions (Australian Academy of Science 2010).

Australian scientists have been measuring greenhouse gases at Cape Grim in Tasmania for 50 years, an area considered to have the cleanest air in the world. During this time, the level of CO2 at Cape Grim has increased linearly from 328 to nearly 400 ppm. Scientists also have measurements of ancient air locked in ice from Antarctica, showing the air and oceans contain more CO2 that at any time in the past 800,000 years.

Warming of the atmosphere and oceans cause complex reactions within the global climate system and this is why there is some level of uncertainty and the possibility of sudden climate shocks.

Scientists use all the information they have on the factors influencing global climate to try and determine the likely effects of increased greenhouse gases on these factors. For example if the oceans warm it will impact on ocean currents and atmospheric circulations and change the position of some of the main climate drivers for the South Coast.

Although there are still many gaps in knowledge about what influences climate in Western Australia, the Bureau of Meteorology and CSIRO can put their current knowledge into their models and evaluate them against past climate to increase confidence in the modeling.

Global Climate models (General Circulation Models)

"Essentially, all models are wrong, but some are useful,” is a well-known quote from statistician G.E.P Box in his book with Norman Draper, Empirical Model-Building and Response Surfaces.

It means that mathematical models cannot perfectly represent reality but they can provide information that helps reduce some of the uncertainty.

Climate models are mathematical representations of global climate systems based on the laws of physics. Climate model projections are tools aimed at reducing the uncertainty as to how the climate will respond to increased atmospheric greenhouse gas concentrations.

General Circulation Models represent physical processes in the atmosphere, ocean, cryosphere and land surface and the data put into the models are large-scale distributions of atmospheric temperature, precipitation, radiation, wind, sea temperatures, ocean currents and sea ice cover.

The models are becoming increasingly complex but are also beginning to show more consistent projections. With increasing computing power there is increasing confidence in the models but it should be remembered that they will only simulate the interactions in the climate systems well if there is a good understanding of the processes that govern the climate system.

Models are evaluated by comparing their predictions to current and past climate and these evaluations are providing increasing agreement and confidence. Projections on temperature are less uncertain than those of rainfall.

Confidence in projections is higher for some models than others. However, some of the global climate models do show the changes that have occurred in the broader region of the south-west in terms of atmospheric instability, storm track modes and rainfall

Although the projections are uncertain, the models simulate the patterns of high and low pressure systems in the westerly wind belts quite well. Therefore there is less uncertainty about the projections of a drying climate in the south-west than other climate projections and 90 per cent of the global models in CMIP3 agreed that the south-west will become dryer.

Nevertheless, projections from global climate models need to be regarded with caution, particularly when dealing with climate at the sub-regional scale. It is very important to recognise their limitations.

Confidence in climate model projections decreases at finer scales, because at finer spatial scales the magnitude of natural variability in climate increases and local influences on climate become more significant.

Although the models are not currently specific to particular parts of the South Coast region, there is strong evidence from south-west projections that much of the region needs to adapt to a warmer and dryer climate, or at least to more frequent hot dry seasons.

The CSIRO and Bureau of Meteorology are producing more fine scaled projections. Some of the terms the scientists use in the projection information they provide to NRM groups are outlined below.

Representative Concentration Pathways

Climate projections have to use an estimate of greenhouse gases in the atmosphere at a given time to determine the impact on future climate. The projections depend on the amount of greenhouse gas emissions and therefore on human activities in the future. This is difficult to calculate and climate modellers need to have a consistent set of scenarios.

In the third and fourth Intergovernmental Panel on Climate Change (IPCC) reports, the Special Report on Emissions Scenarios (SRES) was used,  which were four narrative storylines labelled A1, A2, B1 and B2. Each storyline represented different demographic, social, economic, technological and environmental developments.

To ensure consistency for modelling and projections, in its fifth report, the IPCC decided to use four representative scenarios. These scenarios give an estimate of the extra heat energy (radiative forcing) from emission of greenhouse gases to 2100. They include a pathway of greenhouse gas concentrations, over time to 2100. Models of the carbon cycle are used to convert emissions into atmospheric concentrations of CO2 in parts per million.

The Representative Concentration Pathways (RCPs) are therefore representative of possible future emissions and concentrations of CO2. They include one early mitigation scenario leading to a very low forcing level with a peak and decline (RCP2.6), a stabilisation before 2100 (RCP4.5) and stabilisation after 2100 (RCP6) and one very high emission scenario where there is little action to reduce greenhouse gas pollution and emissions are still rising (RCP8.5) (Table 1). The advantage of using RCPs is they allow consistency in climate modelling.

Table 1 Representative concentration pathways with different scenarios

Early Mitigation, with peak and decline before 2100 2.6 490
Stabilisation before 2100 4.5 650
Stabilisation after 2100 6 850
Emissions still rising after 2100 8.5 >1370

carbon dioxide concentrations 21st cen diagram

Figure 1 Comparison of carbon dioxide concentrations for the 21st century from the RCPs and SRES scenarios. RCP8.5 is closest to A1FI, RCP6 is closest to A1B, RCP4.5 is similar to B1, and RCP2.6 is lower than any of the standard SRES scenarios. The SRES scenarios were used in the third IPCC report. Source: Jubb et al. 2013 (Data from Meinshausen et al 2011 and IPCC TAR WG1 Appendix 2).

Each RCP is a measure of approximate extra radiative forcing in 2100 compared to 1750. Radiative forcing is a measure of the energy absorbed and retained in the lower atmosphere. For an RCP of 8.5, the radiative forcing in 2100 would be 8.5 Watts/m2. That represents the extra warming from greenhouse gas pollution if emissions were still rising at the end of the century. The amount of warming can’t be predicted precisely because other factors could influence the climate systems, but it gives some indication of the consequences of continuing CO2 emissions versus mitigation.

Although the different RCPs don’t show large differences up to 2030 they diverge, particularly after 2100. In other words, even though the climate to mid-century may not be very different under different levels of mitigation, the implications for climate change late in the century and in the next century are much larger.

Climate modeling and particularly climate projections are coordinated through a series of major projects called Coupled Model Intercomparison Projects (CMIP). The ‘Coupled’ refers to the coupling of Ocean General Circulation Models and Atmosphere General Circulation Models. It is now in phase 5 to correspond with the IPCC’s fifth report.

Coupled Model Intercomparison Project Phase 5 (CMIP5)

The Coupled Model Intercomparison Project (CMIP) involves the coordination of a range of climate model experiments and projections. Its objective is to better understand past, present and future climate changes arising from either natural climate variability, or in response to changes as a result of human activities causing increased greenhouse gas emissions.

It collects the output from the global coupled atmosphere general circulation models. Amongst other objectives, CMIP5 provides climate projections out to 2035 and 2100 and beyond. CMIP5 projections include factors that were not included in CMIP3 but which may be important for South Coast Climate. For example CMIP 5 includes ozone hole recovery, which is likely to have an impact on the South Coast climate.

CSIRO and BoM are providing the projections from CMIP 5 to the Regional NRM groups as a tool to assist them in planning for climate change.

Statistical Downscaling and Regional Climate Models

Regional NRM planning requires information at finer spatial scales than provided by the coarse resolution of global climate models. Statistical downscaling is the process used to transform climate information at large scale to higher resolution.

Regional climate models are nested in the global climate model to increase the resolution. The outputs from the global climate model are used as inputs for the regional climate model which contain finer scale information such as land use and topography.

Downscaling does not reduce the uncertainty in the models, but can help to see how well they are behaving in relation to actual temperature and rainfall in a given location, such as a water catchment.

The projections from downscaling must be used with caution as there has been some limited statistical downscaling for small-scale areas of the region in the past. For example Smith et al (2009) used statistical downscaling of the CSIRO Global Climate Model for the Denmark catchment. They found the rainfall distribution in Denmark was different from the actual distribution with the model showing lower rainfall in autumn, winter and spring and higher in summer than the measured rainfall.

The period used can also influence the modeling, because there appears to have been a change in climate drivers from 2000 on the South Coast. Another problem is that different downscaling methods can produce different results.

“It is becoming apparent, however, that downscaling also has serious practical limitations, especially where the meteorological data needed for model calibration may be of dubious quality or patchy, the links between regional and local climate are poorly understood or resolved, and where technical capacity is not in place. Another concern is that high-resolution downscaling can be misconstrued as accurate downscaling.” (Wilby and Dessai, 2010.)

Although the projections for the broader south-west are considered robust, information on local climate influences on the South Coast is more limited so any statistical downscaling provided by CSIRO and BoM needs to be evaluated at a local scale.

Observed changes in climate in the South Coast region

The extent of climate change in the last decade has been variable across the South Coast and the region’s climate has not shown the early drying trend of the west coast.

The west coast has appeared to show an earlier and greater rainfall decline than the global climate models suggested and this is probably partly because of natural variation with a wet period from 1961-1990. It is difficult to separate natural variation from the impact of human activities on climate, but models are helping to differentiate these effects.

The South Coast region has a range of climates, varying from higher rainfall areas in the south-west, to lower rainfall areas in the north-east. These areas have shown different degrees of climate change in the past 40 years.

The baseline for comparison is important because there appear to be two different climate change points; from 1975 for the reduction in low-pressure systems affecting western areas and from 2000, for the increase in high-pressure systems affecting the wider area of the South Coast.

There is currently not enough data available to determine whether the trend from 2000 is a long term one, because natural variability can mask any trends in short term data. The table below shows some comparisons between changes in growing season rainfall for Kojonup, Ravensthorpe and Salmon Gums for the period to 2000.

Table 2 Rainfall change in the last 40 years for Kojonup (Farre et al. 2011 a), Salmon Gums (Farre et al. 2011b) and Ravensthorpe



Changes 1975-2000 v 1939-1974


Changes 1975-2000** v 1939-1974

Salmon Gums

Changes 1975-2000 v 1939-1974

Mean growing season rainfall (April-Oct*) 10% decline 0.17% decrease 2% decline
Rainfall distribution Decrease in June rainfall Increase in May, decrease in June, small decrease in Nov, increase in Dec Decrease in June rainfall, Increase in Nov rainfall

April to October was used as growing season rainfall in the Farre et al (2011 a and b) data for Kojonup and Salmon Gums. If May to October is used growing season rainfall increased slightly in Ravensthorpe.

Comparison of Ravensthorpe to Kojonup and Salmon Gums to 2010 could not be made because of data missing from BoM monthly rainfall statistics for Ravensthorpe for 2003 and 2008

In Kojonup, total annual rainfall from 1975 to 2010 compared to 1939-1974, decreased by 8 per cent, while in Salmon Gums it increased by 5 per cent. The Salmon Gums figures were due to an increase in rainfall outside of the growing season.

Between 2000 and 2010 there was a further decline of 7 per cent in Kojonup’s growing season rainfall and 2 per cent at Salmon Gums. From 1975-2000, Ravensthorpe’s mean annual rainfall declined by 0.9 per cent compared to 1939-1974, while its growing season rainfall fell by 0.17 per cent. Changes in rainfall for Ravensthorpe can be regarded as insignificant.

There is no doubt there has been major climate change in the south-west, which includes much of the western part of the South Coast region. Weather patterns bringing wet conditions have declined and those bringing dry conditions have increased.

This decline in rainfall has corresponded with changes in the large-scale circulation in the southern hemisphere and with a regional scale circulation there has been a decline in the frequency and intensity of high rainfall events.

There has been a reduction in the sub-tropical Jetstream - a strong belt of upper level westerly winds which has led to the reduced likelihood of storms developing. There has also been a weakening of low-pressure systems (from approximately the mid-1970s) and a southward deflection of winter storms.

From the mid-1990s there has been less of a decrease in the low-pressure systems, but an increase in the persistence of high-pressure systems. The increase in high-pressure systems has exerted its influence over a wider geographic area than the decrease, which is why the western part of the region had a drying trend from 2000, while the west coast climate changed much earlier.

Warming in the south has also reduced the temperature gradient between the equator and the pole, which in turn, lessens storm development in WA and increases storms further south in the Southern Ocean at latitudes around 60°S. Several factors, such as natural variation, vegetation cover change and greenhouse gases could have contributed to this change in climate.

North-west cloud bands from the Indian Ocean have increased in the past 50 years, which may be very significant for South Coast rainfall in the early part of the growing season. North-west cloud bands arise off the north-west coast of WA during autumn and early winter and decline in late winter, moving from north-west to south-east.

Interaction of north-west cloud bands with frontal systems can increase rainfall in intensity and spatial area to the south-west. When they interact with frontal systems they bring widespread heavy rainfall but they are related to a number of other major climate influences and so are highly variable.

If the warm ocean origin of these cloud bands moves south with global warming and the expansion of the tropics and they continue to increase, they could increase early winter rainfall in much of the South Coast in the future.

It has been shown, that when there was a high frequency of north-west cloud bands, associated rainfall extended to the central and eastern South Coast, whereas lower frequency rainfall was more limited to western coastal areas.

It is difficult to ascertain the proportion of the drying climate caused by greenhouse gas emissions (greenhouse gas forcing), but modelling suggests that increasing concentrations of greenhouse gases have caused half of the winter rainfall reduction.

Therefore the drying climate in the south-west is likely to be the result of several factors all driving the climate in one direction. The projected increase in SAM (moving further southwards) in the future, suggests a continuation of the drying trend and more frequent dry seasons in the south-west.

Models show the higher the greenhouse gas emissions, the more the high pressure systems will dominate and low pressure systems will move closer to Antarctica. Consequently westerly winds will be much weaker over the south-west, increasing the drying trend.

Maximum temperatures in the region have generally shown a different pattern to the west coast. Maximum temperatures on the eastern part of the south-west (much of the South Coast region) tend to be cooler when SAM is in a high phase due to more easterly winds associated with high-pressure systems.

It has been suggested the Antarctic ozone hole may be responsible for the dominance of high-pressure systems and a subsequent cooling effect in the south-east of WA. Speculation suggests that with the closure of the ozone hole there could be a temporary warming effect on maximum temperatures in the region (with less easterlies) and a temporary cooling effect on the west coast.

Although the ozone hole is projected to close in the next 50 years and this may have some effects on the south-west, the impact of greenhouse gas concentrations is expected to override the effect. The counter effect of these two influences suggests accurately predicting the direction of maximum temperatures in the region to 2030 may be difficult.

Broad trend maps for the south-west from the Indian Ocean Climate Initiative and the Bureau of Meteorology do not completely reflect the changes on the South Coast, including the increases in annual rainfall (mainly summer rainfall) in the eastern parts of the region.

Changes in rainfall map

Changes in rainfall: Southern Agricultural Region, Department of Agriculture and Food 1910-1975 versus 1976-2008.

One of the main problems is the South Coast region appears to respond differently to the large-scale circulation changes than much of the south-west. The eastern and central parts of the South Coast also respond differently to the western parts of the region. The climate is changing but even in the short term it is uncertain how the changes will impact.

Climate Projections from CMIP 5

The interim climate projections for the southern and south-western flatlands cluster (a broad area that includes the whole of the south-west of WA and parts of South Australia) include:

  • Temperature to increase in all seasons
  • More hot days and fewer cold days
  • Decline in winter rainfall
  • Uncertain summer rainfall
  • Extreme rainfall intensity will increase
  • Natural rainfall variability will continue and may mask any trend in average rainfall for some decades particularly in summer.

Uncertainties in climate projections

Uncertainty in climate projections is a challenge when planning for adaptation to changes in climate. There are a number of levels of uncertainties associated with climate projections, including:

  • Emissions scenarios and uncertainties in relation to human activities.
  • Climate models i.e. scientific uncertainties associated with how climate systems behave.
  • Local climate, uncertainties in relation to microclimatic effects.
  • Natural climate variability.
  • Behaviour of complex climate systems interacting with other systems.

The problem is, that the uncertainties multiply and there is a cascade of uncertainty and the uncertainty increases at each level.

 Wilby Dessai

Cascade of uncertainty adapted from Wilby and Dessai 2010

The uncertainties also vary with time. For example, the uncertainty in representation concentration pathways, become more important after 2030. Uncertainties increase even further when modelling for other factors such as distribution of particular species, pests and diseases or agricultural impacts uses global climate models or often just a selection of global climate models.

Planning for climate uncertainty

There are challenges in planning for adaptation to uncertain changes in climate. The National NRM Impact and Adaptation Project (2013) listed the main challenges as:

  • Making decisions for multiple possible futures
  • Employing flexible and adaptive planning processes
  • Explicitly identifying and preparing for likely future decisions
  • Strengthening the adaptive capacity of people and organisations.

Because of the uncertainty about future climate, the Commonwealth Government (Australian Greenhouse Office, 2006) advocated using risk management and adaptive management approaches as a way to deal with the uncertainty.

CSIRO and BoM stress care must be taken in using the climate projections in the risk assessment. It is particularly important to determine the spatial resolution and to consider the uncertainty. The literature on risk management approaches for climate is increasing rapidly and there is a new journal entitled Climate Risk Management dedicated to the discipline. Risk analysis is aimed at reducing or at least specifying the uncertainty so better decisions can be made.

Risk management is defined as a five-step process identifying, analyising and evaluating a risk and plans and implements a strategy to reduce the chances of the undesirable event occurring or reduce the scale of damage caused by the event.

Climate scientists from CSIRO and BoM stress the importance of making sure the scenarios used in risk assessment are internally consistent and under a consistent set of assumptions including choice of global climate models, time period and RCP. They stress the importance of not mixing and matching of projections

Summary and Glossary

Climate change is a controversial topic and there are many different viewpoints across the South Coast region. There are consequently different attitudes to the risk and the need for action.

Most Australian climate scientists believe the evidence for global warming is unequivocal and there will be major impacts on climate. Research through the Indian Ocean Climate Initiative has increased the body of knowledge about the main influences on climate in the south-west.  Nevertheless, the global climate system is very complex and there is a lot of uncertainty about rainfall projections for the region.


Adaptation is defined by the United Nations Framework Convention on Climate Change as an adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities. In simpler terms, adaptation refers to any activity reducing the negative impacts of climate change and/or enables us to take advantage of any opportunities that climate change may present.

Climate in its narrowest meaning is usually defined as the "average weather," over a long period of time but it has a broader meaning about variability and likelihood of events (BoM 2008).

Enhanced greenhouse effect Additional warming due to the increase in greenhouse gases from human activities (BoM 2008)

Greenhouse effect The greenhouse effect is a natural process that warms the Earth’s surface.

Greenhouse gases absorb heat and prevent it being radiated into space. They include water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs).

The absorbed energy warms the atmosphere and the surface of the Earth. This process maintains the Earth’s temperature at around 33 degrees Celsius warmer than it would otherwise be, allowing life on Earth to exist (Australian government Department of Environment,

Jetstream A flat tubular current of air located in the tropopause area in the earth’s atmosphere between the troposphere and the stratosphere. These powerful winds are generated by strong pressure gradients which reflect the great temperature differences at high altitudes. (Australian Bureau of Meteorology.)

Projection is a set of future conditions or consequences, derived on the basis of explicit assumptions. A projectionmay have a probability or likelihood associated with it.

Radiative forcing is a measure of the energy absorbed and retained in the lower atmosphere. It is also used to describe an externally imposed change in the radiation balance. Forcing agents include: greenhouse gases, aerosols, changes in solar radiation, volcanic activity, changes in albedo (reflectivity of the terrain) and changes due to land use.

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Fax: (08) 9845 8538

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