The modelling rests on a future scenario developed by the Intergovernmental Panel on Climate Change known as SSP2-4.5. This intermediate scenario, combining moderate greenhouse gas emissions with a partial global policy response, points to roughly 2.7 degrees Celsius of average global warming above pre-industrial levels by 2100. That figure is broadly in line with where existing national pledges and policies are steering the planet, but it sits well above the 1.5 degree threshold that world leaders enshrined in the Paris Agreement as the aspirational safe limit for climate change. In other words, the study’s headline losses are not a worst-case projection; they are close to business as usual.

To translate rising water into rising bills, the research team followed a deliberately systematic approach. They first mapped the areas likely to be inundated by combining sea-level projections with estimates of storm surge and high-resolution elevation data across the Australian continent. Within those flood-exposed zones, they then identified every affected property and parcel of land, drawing on a wide range of data sources and empirical measures to estimate the value of homes, farms, roads, utilities, ecosystems and agricultural acreage. The result was a granular national picture of exposure that no previous Australian study had assembled at this scale.

The second stage of the analysis converted exposure into expected harm. Using statistical modelling, the researchers estimated how severely the assets inside the mapped flood zones could be damaged over time as sea levels climb and storm surges push further inland. The physical damages projected by the model were then translated into economic losses, yielding a nationwide damage function that captures the compounding interaction between higher seas, extreme coastal water levels and the value of what lies in the water’s path. The method is a computational simulation grounded in observed relationships, designed to give policymakers a defensible estimate of future costs rather than an abstract warning.

The geographic distribution of the projected losses is striking. Every state and the Northern Territory will bear significant economic costs, the study finds, ranging from 230.5 billion dollars in Western Australia down to 7.9 billion dollars in Tasmania. Queensland follows close behind Western Australia with projected losses of 214.5 billion dollars, then Victoria at 167 billion dollars, New South Wales at 151 billion dollars, South Australia at 49.2 billion dollars and the Northern Territory at 35.2 billion dollars. The pattern reflects the combination of long, low-lying coastlines, dense coastal development and the sheer value of the property and infrastructure concentrated along Australia’s populated edges.

Property counts tell a parallel story of exposure. Queensland has the greatest number of properties at risk, with 93,157 identified in the flood-exposed zones, followed by New South Wales with 71,210 and Western Australia with 51,366. Yet within these state-wide totals, a single urban hotspot stands out. The Gold Coast alone faces 84.4 billion dollars in projected economic losses, making it the most exposed urban area in the entire country. The finding will resonate with residents who watched Tropical Cyclone Alfred tear away stretches of beach in a single night, an event that cost the City of Gold Coast 35 million dollars in emergency beach repairs and left communities along the east coast still recovering.

Despite the enormous sums, the study’s authors stress that their estimate is conservative in several important respects. The modelling uses a middle-of-the-road emissions scenario, holds storm intensity constant rather than allowing it to intensify with warming, and excludes losses from coastal erosion altogether. Perhaps most significantly, the figures do not reflect the possibility of rapid collapse of the Greenland and West Antarctic ice sheets, which could add up to two metres of global sea level rise by the end of the century. If any of those factors worsen, the true bill for coastal Australia could climb far beyond the 855 billion dollar floor that the study establishes.

The human dimension behind the numbers is considerable. The majority of Australians live within 50 kilometres of the coastline, meaning sea level rise may physically affect a large share of the national population. Millions of hectares of land are at risk by 2100 on current projections, and the damages extend well beyond housing to essential infrastructure, ecosystem services and valuable agricultural land. Professor Tom Kompas of the University of Melbourne, who led the study and co-authored the Climate Council’s accompanying Rising Seas Rising Bills report, notes that because carbon emissions have remained too high, a certain amount of sea level rise is already locked into the system. Adaptation, he argues, is no longer optional; the least costly option available is to avoid building new development in the places where risks are known to be highest, while restoring coastlines and reforming construction practices to reduce future exposure. These are hard decisions, he acknowledges, but they are ones communities are already confronting.

Climate scientists involved with the accompanying report emphasise that the mechanics of the threat are deceptively simple. Storm surges do not need to become more frequent or more violent to cause escalating damage; they simply ride on higher baseline seas, pushing floodwaters deeper into neighbourhoods that once stayed dry. Adjunct Professor Andrew Watkins, a Climate Councillor and co-author of the report, warns that powerful storm surges are already putting coastal homes and infrastructure at greater risk, and that economic losses can skyrocket into hundreds of billions of dollars if action is delayed. He describes sea level rise as a slow-onset disaster, one that demands faster cuts to greenhouse gas pollution alongside serious preparation of vulnerable communities, and cautions that the rapid loss of ice sheets and glaciers could push oceans even higher than the study’s already sobering projections.

What makes the research a landmark for Australia is its completeness. Previous assessments have tended to examine individual regions, cities or asset classes, leaving policymakers without a coherent national figure to weigh against adaptation investments. By modelling every state and territory under a single consistent methodology and anchoring the results to an internationally recognised emissions scenario, the study provides a common baseline for planning debates about coastal development, insurance, infrastructure design and managed retreat. The 855 billion dollar figure is, in effect, a price tag on the coast as it exists today, and a measure of how much cheaper the future could be if emissions fall faster and the most dangerous development choices are avoided. As the century advances and the seas continue their measured climb, the study suggests that the costliest decisions will not be about whether to protect Australia’s coastline, but how quickly the nation accepts what the water is already telling it.

Subject of Research: Nationwide economic impacts of sea level rise and storm surge from global warming in Australia

Article Title: Rising sea levels could cost Australians at least $855 billion by 2100

Article References: Rising sea levels could cost Australians at least $855 billion by 2100. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: sea level rise, storm surge, Australia, coastal flooding, economic losses, climate change, IPCC scenarios, SSP2-4.5, Gold Coast, Scientific Reports, coastal adaptation, property risk