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.

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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