Climate Change in the NAR
Australia’s changing climate represents a significant challenge to individuals, communities, governments, businesses and the environment. Australia has already experienced increases in average temperatures over the past 60 years, with more frequent hot weather, fewer cold days, shifting rainfall patterns, and rising sea levels.
To assist the planning and management of Natural Resource Management regions, CSIRO and the Australian Bureau of Meteorology have prepared climate change projections for eight regions of Australia, termed NRM clusters.
The Northern Agricultural Region is part of the Southern and South-Western Flatlands (SSWF) cluster, comprising NRM regions in southwest Western Australia and southern South Australia.
Climate projections for SSWF are based on the outputs of a set of 40 global climate models developed by Australian and international scientists. The projections are the most comprehensive ever released for Australia. For more information view the full report or for easy communication of their findings view the 8 page brochure.
For information about these models and climate scenarios, please visit the Climate Change in Australia website.
Summary of Climate Change Projections for the South West of WA
Average temperatures will continue to increase in all seasons
- Very high confidence – continued substantial increases in projected mean, maximum and minimum temperatures.
- For the near future (2030), the annually averaged warming across all emission scenarios is projected to be around 0.5 to 1.1˚C above the climate of 1986-2005. By late in the century (2090), for a high emission scenario (RCP8.5) the projected range of warming is 2.6 to 4.0˚C.
- The projected multi-model median temperature. Half the models have projections above, and half below, this line.
- 10th to 90th percentile of projected 20-year average climate. 80% of model results lie in this range.
- 10th to 90th percentile of individual years (taking into account year to year variability). 80% of years lie in this range.
- The observed time-series for 1910–2013 is overlaid on the simulated climate for the corresponding period (grey line and shading as per 1–3).
- One climate model is shown to illustrate how the warming future may unfold. Note that models simulate realistic variability in annual temperature.
Image source: CSIRO
Hotter and more frequent hot days, less frost
- Very high confidence – substantial increases in the maximum temperature on the hottest days, the frequency of hot days and the duration of warm spells are projected.
- High confidence – a decrease in the frequency of frost days is projected.
Average annual number of days above 35 and 40°C for Perth for the 30-year period centred on 1995 (1981-2010) and for future 30-year periods (centred on 2030 and 2090).
Image source: CSIRO
Less rain in winter and spring, changes in other seasons unclear.
- High confidence – decreases in winter and spring (and annual) rainfall.
- By 2030 winter rainfall may change by -15 to +5%. By 2090, these ranges are around -30 to -5% under RCP4.5 and -45 to -15% under RCP8.5.
- Changes in autumn and summer are unclear.
Projected rainfall differences (%) for three RCPs for the southern and south-western flatlands sub-clusters for 20 years centred on 2090 (2080–2099 period) compared to 1986–2005. Bars indicate the 10th to 90th percentile range of model results.
Image source: CSIRO
Increased intensity of heavy rainfall events, drought duration to increase
- Medium confidence – intensity of heavy rainfall events will increase.
- This increase is projected despite projected decreases in mean rainfall. Projections of the magnitude of change have low confidence and therefore the time when any change may be evident against natural variability cannot be reliably projected.
- Under all RCPs, and at all time periods into the future, the time spent in meteorological drought is projected to increase compared to the present climate. These increases become quite marked by 2090 under RCP8.5. The projected changes are strongly driven by the projected decline in annual rainfall and are of high confidence.
Projected changes in annual average rainfall, rainfall on the wettest day per year and rainfall on the wettest day in 20 years, for 2080–2099 compared to 1986-2005.
Changes are given in percentage with respect to the 1986-2005 mean for RCP4.5 (blue) and RCP8.5 (purple). Natural climate variability is represented by the grey bar.
Bars indicate the 10th to 90th percentile range of model results.
Image source: CSIRO
Decrease in winter mean wind speed
- High confidence – small changes in mean surface wind speeds under all RCPs by 2030.
- High confidence – decreases in winter mean surface winds for 2090 under RCP4.5 and RCP8.5 based on model results and physical understanding (relating to decreased storminess).
- Medium confidence – decreases are suggested for extreme wind speeds, particularly for the rare extremes under both RCP4.5 and RCP8.5.
Increased solar radiation and reduced relative humidity in winter and spring
- High confidence – little change to solar radiation by 2030.
- High confidence – an increase in winter radiation by 2090, under RCP4.5 and RCP8.5 (5 and 10% increase respectively).
- Medium confidence – an increase in spring radiation (about half of that expected in winter) by 2090, under RCP4.5 and RCP8.5 and little change in summer and autumn.
- High confidence – little change in relative humidity by 2030.
- High confidence – decrease in relative humidity for winter and spring by 2090 (up to 5% under RCP8.5).
Increased evaporation rates, and reduced soil moisture and runoff
- High confidence – increases in potential evapotranspiration in all seasons with the largest absolute rates projected in summer by 2090.
- Medium confidence – in the magnitude of evapotranspiration projections due to shortcomings in the simulations of observed historical changes.
- High confidence – decreases in rainfall and increases in potential evapotranspiration are projected to lead to a decrease in soil moisture and runoff by 2090 under both RCP4.5 and RCP8.5
A harsher fire-weather climate in the future
- High confidence – climate change will result in a harsher fire-weather climate in the future
- Low confidence – in the magnitude of the change as this is strongly dependent on the summer rainfall projectio
Higher sea levels and more frequent sea-level extremes
- Very high confidence – sea level will continue to rise during the 21st century.
- By 2030, the projected range of sea level rise at Fremantle is 0.07 to 0.17 m above the 1986-2005 level, with only minor differences between emission scenarios. As the century progresses, projections are sensitive to emissions pathways. By 2090, RCP4.5 gives a rise of 0.28 to 0.65 m and RCP8.5 gives a rise of 0.39 to 0.84m. These ranges are considered likely (at least 66% probability). However, if a collapse in the marine based sectors of the Antarctic ice sheet were initiated, these projections could be several tenths of a metre higher by late in the century.
- Taking into account the nature of extreme sea levels along the southern and south-west flatlands coastlines and the uncertainty in the sea level rise projections, an indicative extreme sea level ‘allowance’ is provided. The allowance being the minimum distance required to raise an asset to maintain current frequency of breaches under projected sea level rise. In 2030, the vertical allowances along the cluster coastline are in the range of 11 to 13 cm for all RCPs, and by 2090, 48 to 56 cm for RCP4.5 and 66 to 76 cm for RCP8.5.
Observed and projected relative sea level change (m) for Fremantle (which have continuous records available for the period 1966–2010). The observed tide gauge relative sea level records are indicated in black, with the satellite record (since 1993) in mustard and tide gauge reconstruction (which has lower variability) in cyan. Multi-model mean projections (thick purple and olive lines) for the RCP8.5 and RCP2.6 scenarios with uncertainty ranges shown by the purple and olive shaded regions from 2006–2100. The mustard and cyan dashed lines are estimates of inter-annual variability in sea level (uncertainty range about the projections) and indicate that individual monthly averages of sea level can be above or below longer term averages. Note that the ranges of sea level rise should be considered likely (at least 66 % probability) and that if a collapse in the marine based sectors of the Antarctic ice sheet were initiated, these projections could be several tenths of a metre higher by late in the century.
Image source: CSIRO
Warmer and more acidic oceans in the future
- Very high confidence – warming of sea surface temperature (SST) across the globe is projected to continue.
- Across the coastal waters of the southern and south western flatlands region in 2090, warming is projected in the range of 1.5 to 3.9˚C for RCP8.5.
- Continued acidification will compromise the ability of calcifying marine organisms such as corals, oysters and some plankton to form their shells or skeletons.
- Very high confidence – around Australia the ocean will become more acidic.
- High confidence – the rate of ocean acidification will be proportional to carbon dioxide emissions.
- By 2030, pH is projected to fall by up to additional 0.08 units in the coastal waters of the cluster. By 2090, pH is projected to fall by up to 0.15 under RCP4.5 and up to 0.33 under RCP8.5. These values would represent an additional 40% and 110% in acidity respectively.
Source: Hope, P.et al. 2015, Southern and South-Western Flatlands Cluster Report, Climate Change in Australia Projections for Australia’s Natural Resource Management Regions: Cluster Reports, eds. Ekstrom, M. et , CSIRO and Bureau of Meteorology, Australia.