Australia’s Projections


ClimateChange–

Australian Climate Variability and Change

Information below taken from CSIRO’s Climate Change in Australia. Information for Australia’s Natural Resource Management Regions: Technical Report (2015). The report can be accessed here.

Projected changes have been prepared for four Representative Concentration Pathways (RCPs) used by the latest IPCC assessment (CMIP5).

RCP2.6 – requiring very strong emission reductions from a peak at around 2020 to reach a carbon dioxide (CO2) concentration at about 420 parts per million (PPM) by 2100
RCP4.5 – slower emission reductions that stabilise the CO2 concentration at about 540 ppm by 2100
RCP8.5 – assumes increases in emissions leading to a CO2 concentration of about 940 ppm by 2100.

Confidence ratings for the projections are based on the judgement of the authors derived from multiple lines of evidence.

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Australia has been warming and will warm substantially during the 21st Century.

  • very high confidence – continued increases of mean, daily minimum and daily maximum temperatures throughout this century for all regions in Australia
  • high confidence – warming will be large compared to natural variability in the near future (2030)
  • very high confidence – warming will be very large compared to natural variability late in the century (2090) under RCP8.5

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More frequent and hotter hot days and fewer frost days are projected.

  • very high confidence – more frequent and hotter hot days and warmer colder extremes
  • high confidence – reduced frost

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Mid-latitude weather systems are projected to shift south in winter and the Tropics to expand.

  • high confidence – observed intensification of the subtropical ridge and expansion of the Hadley Cell circulation are projected to continue in the 21st century.
  • high confidence – in winter, mid-latitude weather systems are projected to shift south and the westerlies are projected to strengthen.

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Cool-season rainfall is projected to decline in southern Australia; other changes to average rainfall are uncertain.

  • high confidence – in southern Australia, cool season (winter and spring) rainfall is projected to decrease.

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Extreme rain events are projected to become more intense.

  • high confidence – extreme rainfall events (wettest day of the year and wettest day in 20 years) are projected to increase in intensity throughout most of Australia.
  • medium confidence – in increased rainfall intensity for south-western Western Australia, because of the large projected reduction in mean rainfall in this region.

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Time in drought is projected to increase in southern Australia, with a greater frequency of severe droughts.

  • high confidence – time in drought (as measured by Standardised Precipitation Index) is projected to increase over southern Australia.
  • medium or low confidence – time in drought is projected to increase in other regions.
  • medium confidence – greater frequency of extreme droughts, and less frequent moderate to severe drought projected for all regions.

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Snowfall in the Australian Alps is projected to decrease, especially at low elevations.

  • very high confidence – as warming progresses there will be a decrease in snowfall an increase in snowmelt and thus reduced snow cover.

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Small changes in wind speed.

  • high confidence – by 2030, changes in near-surface wind speeds are projected to be small compared to natural variability
  • high confidence – by 2090, wind speeds are projected to decrease in southern mainland Australia in winter.

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Tropical cyclones may occur less often, become more intense, and may reach further south.

  • medium confidence – based on global and regional studies, tropical cyclones are projected to become less frequent with a greater proportion of high intensity storms (stronger winds and greater rainfall).
  • low confidence – a greater proportion of storms may reach south of latitude 25 degrees South.

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More sunshine is projected in winter and spring, with lower relative humidity and higher evaporation rates through the year.

  • high confidence – little change in solar radiation over Australia in the near future (2030).
  • medium confidence – increase in solar radiation in winter and spring in southern Australia late in the century (2090).
  • high confidence – by 2030, decreases in relative humidity in inland regions and where rainfall is projected to decline is expected to be relatively small.
  • high confidence – by 2090, humidity will decrease in winter and spring as well as annually.
  • medium confidence – declining relative humidity in summer and autumn.
  • high confidence – increasing potential evapotranspiration (atmospheric moisture demand) closely related to local warming, although there is only medium confidence in the magnitude of change.

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Soil moisture is projected to decrease and future run-off will decrease where rainfall is projected to decrease.

  • high confidence – decreasing soil moisture in the southern regions (particularly in winter and spring) driven by the projected decrease in rainfall and higher evaporative demand.
  • medium confidence – decreasing soil moisture elsewhere in Australia where evaporative demand is projected to increase but the direction of rainfall change is uncertain.
  • high confidence – decreases in runoff in south-western Australia and southern South Australia
  • medium confidence – decreases in runoff in far south eastern Australia, where future rainfall is projected to decrease.

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Southern and eastern Australia are projected to experience harsher fire weather; changes elsewhere are less certain.

  • high confidence – increases in the average forest fire danger index and a greater number of days with severe fire danger in southern and eastern Australia.
  • medium confidence – there will be little change in fire frequency in tropical and monsoonal northern Australia.

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Sea levels will continue to rise throughout the 21st century and beyond; extreme sea levels will also rise.

  • very high confidence – Australia sea levels are projected to rise through the 21st century, in line with global mean sea level.
  • high confidence -very likely to rise at a faster rate during the 21st century than over the past four decades, for the range of RCPs considered.
  • medium confidence – Sea level projections for the Australian coastline by 2090 (average of 2080 to 2100) are comparable to, or slightly larger than (by up to about 6 cm) the global mean sea level projections of 26-55 cm for RCP2.6 and 45-82 cm for RCP8.5.
  • medium confidence – main contribution to increasing extreme sea levels is from the rise in mean sea level.
  • low confidence – contributions to extreme sea levels from changes in weather events are projected to be small or negative.

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Oceans around Australia will warm and become more acidic. Salinity may also change.

  • very high confidence – sea surface temperatures around Australia will rise.
  • low confidence – a net reduction in the salinity of Australian coastal waters is projected. For some southern regions, models indicate an increase in sea surface salinity, particularly under higher emissions.
  • very high confidence – around Australia the ocean will become more acidic, with a net reduction  in pH.
  • high confidence – the rate of ocean acidification will be proportional to carbon dioxide emissions.
  • medium confidence – long term viability of corals will be impacted under RCP8.5 and RCP4.5, and that there will be harm to marine ecosystems from the projected reduction in pH under RCP8.5.

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