What are the most likely climate changes for Australia over the next 50 years or so.

By David Holland

In the latest IPCC assessment report 5 (AR5), entitled Southern Hemisphere extra-tropical circulation, it is suggested that because of the ozone layer hole recovering over the next few years due to better regulation of CFCs there will not be a southern shift to the Cyclone belt. This will mean that Sydney will likely not get tropical cycles in the next 50 years.

The section of the AR5 entitled, Changes in evaporation, evaporation minus precipitation, runoff, soil moisture, relative humidity and specific humidity, suggests that Australia in the southern hemisphere will have higher evaporation over oceans and less evaporation with more rainfall in coastal regions over the next 50 years.

The report shows that there will be more precipitation in higher latitudes and less in lower latitudes. However local condition around Sydney may influence weather such as anthropogenic aerosol emissions, which could bring a cooling and more precipitation. (IPCC, AR5 working Group 1)

As global average temperatures rise the wetter areas in Australia such as Sydney are expected to get wetter and dryer areas are expected to get dryer.

The El Niño southern oscillation and Indian Ocean Dipole will work with or against climate change in both Sydney and Perth respectively.

From data predicted from the AR5 document in section, Regional and seasonal patterns of surface warming, it is expected that there will be an intensification of energy transfer from the oceans to the land. This will increase coastal breeze wind speeds and intensify rain and storm events at a local scale.

This energy transfer will increasingly bring warmer nights and more humid conditions to coastal urban areas.

In the section of the report, Global mean surface air temperature it suggests that the 5% to 95% data from the multi-model mean would be 0.39 to 0.87 degrees increase in global average temperatures. This would confirm the increase in ocean temperatures and suggest that inland Australia would be effectively much hotter than today.

Chapter 5 of the Garnaut review outlines the future climate scenarios for Australia.

It suggests that a 1% increase in temperature will have a 15% reduction in stream flow. If this is the case then water may become more of a problem in the bush as global warming takes hold.

If there is a 10% drop in rainfall this would reduce stream flow by 35%. (Jones et al. 2001 cited in Garnaut CSIRO (2008)).

The report suggests there has been a trend of more bush fires and more intensive ones coupled with more hotter days. This is normally a recipe for drying out fuel for fires, which can be done on these extreme hot days within hours. Lucas et al. 2007 cited in Garnaut (2008) suggests that fire season will start earlier and finish later in the bush fire season.

A study of projected temperatures by Lucas et al. 2007 cited in Garnaut (2008) suggests that a 1 degree C increase in average global temperature will give 20 locations of catastrophic fire in Australia and reoccurring within 16 years. A 2.9 degree increase will give 22 locations, 19 of which are reoccurring within 8 years and three reoccurring within 3 years.

This type of fire regime may seem costly to land holders and insurance premiums will rise, but it will hit very hard on ecological systems and their recovery after a catastrophic fire. Then if the location is burnt on multiple occasions within the 7 to 10 year period a very great potential for species inhalation from that locality is highly likely.

Figure 5.3 of the report shows a prediction of 0.6 to 5.0 degrees between 2030 to 2100 for Sydney and Perth with the inland regions about a degree hotter.

The report indicates that seasonal variations could mask rain event intensity due to anthropogenic climate change. It suggests that rain event intensity will probably increase but overall average rainfall may remain the same.

Abbs et al. (2006) cited in Garnaut (2008) suggests that category 3-5 cyclones will increase in intensity by 60% by 2030 and 140% by 2070.

Although Garnaut recognizes the plight of other Asiatic countries and particularly Island atoll’s susceptibility to climate change induced sea level rise, he omits to say anything about Australia being impacted except by refugees from these places. (Garnaut (2008) Chapter 6)

Australia will be hit hard by rising sea levels and Garnaut suggests that there will be some higher floods and storm surges increases due to sea levels rising, no more than some adaptations to materials used in building will be necessary. (Garnaut (2008) Chapter 15)

Holland (2015), outlines that based on the IPCC fourth report the NSW State government in 2009 made councils review flood levels and ensure that no new development was made on at risk land. Sea Level rise is likely to affect coastal regions and development patterns over the next 50 years or so and impact of ecological systems such as salt marsh and wetland environments.
The type of Australia we will expect to see will be in the A2 scenario where the government has not found the courage to take the hard decisions and change the economy to a renewable energy and an environmentally protective economy. The big business mentality will probably prevail with fragmented prosperity and we will be going through a very tough time with mitigating anthropogenic climate change.

References:

Garnaut Ross, (2008),  The Garnaut review, Chapter 5, 6, 15, Projecting Australian climate change, CSIRO, http://www.garnautreview.org.au/pdf/Garnaut_Chapter5.pdf, Accessed Sept. 2016

Holland David, (2015), Planning for Sea Level Rise Risk in some Coastal Regions of Australia – A Market Approach, For Land Potentially Effected by Flood till the year 2100, originally drafted 2010, Habitat Town Planning Forum web page, https://habitattownplanningforum.files.wordpress.com/2015/04/planning-for-climate-change-the-risk-model-for-sea-level-rise-discussion-paper-3rd-edition-rev1-20151.pdf, cited September 2016

IPCC, Climate Change 2013, The Physical Science basis, AR5 working Group 1: Near term Climate Change: Projections and Predictability, Chapter 11, Section The Water Cycle, Changes in Precipitation.

 

 

 

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