Wollongong City Council is considering a future where the city CBD could be underwater.
At Monday night's council meeting councillors will discuss the climate change adaption plan, which includes an expected temperature rise of 3-4 degrees - something Greens councillor Mithra Cox said was "extremely alarming".
"Climate scientists are sounding the alarm bells louder than ever," Cr Cox said.
"The sixth Intergovernmental Panel on Climate Change report released earlier this year - which spells out what the world would look like if we allow it to reach three degrees of warming, and it isn't pretty.
"For Wollongong, this means suburbs like Primbee, Wollongong CBD, East Corrimal and Thirroul will be heavily impacted by sea level rise and coastal erosion.
"If we continue on this trajectory where we reach three degrees warmer, we will have to hold some very difficult conversations with citizens as homes and council's infrastructure, such as parks, reserves, footpaths, roads, and other services, will be increasingly threatened in the coming decades."
Cr Cox said such a rise in temperature would mean the city making a "managed retreat" from the coast would be the only "sensible option" but that realisation may not hit most people until it is too late.
"It means that the conditions we experienced in the black summer bushfires of 2019-2020 will become our experience of a normal summer," she said.
"The 1998 floods that devastated Wollongong - we saw cars floating down creeks, fridges floating out of houses and countless homes inundated - will become an annual event rather than one-in-100 year events," Cr Cox said.
However, the councillor said it wasn't too late to change this "catastrophic trajectory", citing the example of the COVID vaccine as an instance of how fast innovation can occur.
"We have to act now. This will mean drastically ramping up our efforts to reduce greenhouse emissions in the next decade," Cr Cox said.