Waves crash against a garden swimming pool that was washed away from a property on the beach front after heavy rain and storms at Collaroy in Sydney's Northern Beaches.
Waves crash against a garden swimming pool that was washed away from a property on the beach front after heavy rain and storms at Collaroy in Sydney's Northern Beaches. DAVID MOIR

'It's only a matter of time before this happens here'

THE destruction of homes on Sydney's northern beachfront was both a sign of things to come and the bullet the Sunshine Coast dodged when last week's east coast low moved south.

Leading climate change scientist University of the Sunshine Coast professor Patrick D. Nunn said the consequences of global warming on sea level rise would become impossible for even sceptics to dismiss within 20 years.

The process has become irreversible regardless of steps under way to reduce carbon emissions.

Professor Nunn, who contributed to the International Panel on Climate Change's latest report said sea level rise at 3mm a year had been evident since 1996 and by the end of the century the rate of rise would double.

"Emission reduction may affect temperatures but it won't affect sea levels," he said.

"In the short term we will need to adapt to the fact sea levels are rising and will impact exposed places like Sydney's northern beaches.

"But there will need to be long-term strategies because the rate of increase will accelerate."

Prof Nunn said within 20 years when situations like those now occurring at Narrabeen and Collaroy were happening regularly at the rate of once a year the "penny will drop" for those unwilling to accept the changes already occurring.

Sea level rise coupled with more frequent extreme weather events would combine to bring enormous pressure on the densely-populated coastal zone.

"Development in low lying coastal areas will either have to be massively engineered, which would decrease their value or long-term strategies put in place to move to less exposed areas," Prof Nunn said.

Professor Nunn said in the Pacific Islands, where much of his research is conducted, those conversations were already being held and they were facing the expected resistance to change.

He said people once could accept a one-in-100-year event bringing water through their front doors. Those events were now occurring once every 10 years and would increasingly become annual events and apparent to everyone.

"Sea levels are demonstrably rising," he said.

"We dodged a bullet up here (last week) but we are moving back into a La Nina period, which brings a wetter Australia and more cyclonic activity and storms across the Queensland coast."

Those extreme moist conditions with full tides occurring again through summer could make for more extreme weather events.

Sea-level change is a key area of Prof Nunn's research. He was a Lead Author on the most recent IPCC Report (AR5, 2014) on the chapter on Sea Level Change.

Sunshine Coast Council environmental portfolio head Jenny McKay on Wednesday told the ABC the issue was being taken seriously and would ultimately cost the region millions of dollars.

At Collaroy Beach seven homes were severely damaged by huge waves that ate away 50m of the coastline.

Owners were not insured for the damage and face a $5m bill to build a seawall to protect their homes.

Northern Beaches Council said there had been a failure at the time to resolve the dispute.

The Queensland and Government has announced a $12m package to assist local authorities mitigate climate change impacts.