Sutherland Shire Council has adopted a sea level rise projection based on “best information available” and from the agreement reached by the 2015 United Nations Climate Change Conference in Paris.
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The council is required by the State Government to adopt a sea level rise policy and has decided to adopt the recommendation of the Paris conference to limit global temperature rise to less than two degrees.
This equates to an RCP of 6.
RCP, or Representative Concentration Pathways, is the measure of carbon particles in the air.
Accordingly, the council has adopted the sea level rise projections associated with RCP 6 to be used in its future sea level rise projections.
The council’s modelling affects around 4300 homes along the Georges River, particularly around Gwawley Bay and Woolooware.
There are four possible levels that council can adopt - RCP 2.6 with equates to low emissions, an RCP of 4.5 or intermediate emissions, RCP of 6 which also equates to intermediate emissions, and RCP 8.5 high emissions.
With RCP 8.5, it is projected that the sea level rise in 2050 would be 26cm and would accelerate to 98cm in 2100.
Based on RCP 6, the sea level rise would be 23cm by 2050, and in 2100 it would accelerate to 72cm.
The council in the past was leaning towards using RCP 8.5, based on CSIRO modelling.
But a few councillors were uncomfortable with adopting an RCP of 8.5
“The modelling includes a number of factors such as future fuel use, population level and the amount of land cleared,’’ Councillor Tom Croucher said.
‘’Then there is the assumption that the number of carbon particles in the air will affect the temperature.
‘’The next assumption is that it will cause sea level rise and that increased carbon particles will transfer to an increase in temperature of four degrees by the end of the century.
‘’If we go to the worst case scenario of 8.5, we would see a sea level rise of 98cm by the end of the century.
“What this means for any big infrastructure in the shire you have got to put your building 98cm higher.’’
‘’Following the Paris Conference in 2015 we started working on carbon particles equivalent of RPC 6.
‘’The very moment the rest of the world starts going to RCP 6 the council can argue that it can base its projections on RCP6 which equals 72cm.
“The argument I put to the council is that these figures are being constantly revised.
‘’We thought in the interests of protecting the residents from unnecessary costs in building and in minimise their insurance costs we should adopt RCP 6.
“It could mean a difference of thousands of dollars in insurance premiums and a massive impost on infrastructure.
“We felt that adopting RPC 6 was being responsible in that it was supported by the latest science.
“The difference between 6 and 8.5 up to 2050 is only 3cm.
‘’Even up to 2060 it is only 7cm. After 2060 it accelerates.’’
Eurobodalla Shire and Shoalhaven councils have adopted sea level rise scenarios of RCP 6.
Gosford has adopted RCP 8.5.
The majority of other NSW councils have adopted projections for sea level rise using the benchmarks of the State Government from 2009 - 40cm by 2050 and 90cm by 2100.
These benchmarks have since by dropped by the State Government and councils have been encouraged to adopt their own benchmarks based on the best possible information.
A report by council staff recommended that Sutherland Shire Council adopt the higher level scenario of RCP8.5
RCP8.5 represents the scenario that most accurately reflects actual emissions growth observed in the last eight years, a council report said.
But Cr Croucher moved to adopt RPC 6.
“We are obliged to adopt this on the best science available,’’ he said.
“I think we are making a very responsible decision. We can change our position as the science becomes better.’’
Although a global agreement of 187 nations on the reduction of of greenhouse gas emission was negotiated at the 2015 Paris Climate Conference, all government representatives are yet to sign the agreement.
Government representatives are currently meeting in Germany to discuss the next stop leading towards the signing of an agreement.
The new draft sea level rise policy will be on public exhibition from June 22 until July 21.