The reality of climate change means that low-lying coastal cities are becoming what we call “stranded assets.” This is defined by financial analysts as “something that has become obsolete or nonperforming well ahead of its useful life, and must be recorded on a company’s balance sheet as a loss of profit.” How can an entire metropolis be considered “nonperforming?” Consider the example of Miami. The physical installations, infrastructures and architecture upon which Miami are founded were built on what we now can see as a flawed assumption: that the sea’s surface would stay as it had for the entirety of human experience. That’s not happening, and the city is already suffering from flooding even when it’s not raining. When the irrational exuberance about the value of coastal real estate pops and thousands of buyers collectively mark down those assets, it will make the housing bubble of ten years ago look like a small blip. The consequences will reverberate through the economy, through society and through the political landscape.

There was a time a decade or two ago when society could have made a choice to write off our massive investment in a fossil fuel-based economy and begin a policy driven shift towards a cleaner renewable infrastructure that could have forestalled the worst effects of climate change. But the challenges of collective action, a lack of political courage, and the power of incumbent pecuniary interests to capture the levers of power meant we did not. The bill is now coming due.

That means that many of our great, low-lying coastal cities are what we call “stranded assets.” GreenBiz founder Joel Makower defines a stranded asset as “a financial term that describes something that has become obsolete or nonperforming well ahead of its useful life, and must be recorded on a company’s balance sheet as a loss of profit.” Makower was talking about Exxon and other companies that built their businesses on the combustion of climate changing fossil fuels, not cities. But the concept easily transfers from businesses built on carbon to cities threatened by carbon’s impact.

Consider Miami. An invaluable, irreplaceable cultural jewel that will be stranded, both figuratively and literally, by climate change.

How can an entire metropolis that encompasses the lives, culture, and wellbeing of millions be considered “nonperforming?” The physical installations, infrastructures, and architecture upon which Miami are founded were built on what we now can see as a flawed assumption. An assumption of permanence. That the sea’s surface would stay as it had for the entirety of human experience. That Atlantic hurricane season would send infrequent storms of knowable magnitude that we could prepare for and ride out. It was that perception of permanence and predictability that underlay urban planning and shaped of tens of thousands of investment decisions that fostered billions of dollars of wealth in Miami. As long as nothing disturbs that perception, value will continue to accrue on paper. But if the perception of permanence that underlies those expectations is undercut, market value will disappear. Value is in the eyes of the buyer… until its not.

Climate change in general, and sea level rise in particular, are hard for us to see. The tides that surround Miami are elevating at a rate of centimeters per year. It is a slow motion train wreck that will be measured in decades, not seconds. For now, Miami property buyers don’t see it. A 2017 survey found that the majority of property buyers (over two-thirds) don’t ask even their brokers about the implications of climate change and sea level rise on the properties they are buying.

But for those willing to look, the impacts of sea level rise are already evident. So-called “sunny day flooding”, (i.e tidal flooding or flooding that occurs without the rain) is already occurring predictably in many parts of Miami, inundating streets, blocking traffic, killing lawns, corroding infrastructure and cars, contaminating groundwater, and reversing sewage systems. As sea level rise worsens, the inescapable conclusion is that some point Miami will be inundated and unlivable. Absent a civil engineering miracle, the entire city will become a stranded asset that society will have to write off. And it’s not alone: Reuters estimates at least $1.4 trillion in property is sitting within 700 feet of the U.S. shoreline, but the number is much probably larger.

When the irrational exuberance about the value of coastal real estate pops and thousands of buyers collectively mark down those assets, it will make the housing bubble of ten years ago look like a small blip.

The consequences will reverberate through the economy, through society and through the political landscape. Depending on what Hurricane Irma does, we could get a sobering preview of what that will look like. We have already seen the devastation caused by Hurricane Harvey in Houston, a city that was also built on the flawed founding assumption of permanence. Houston’s city planners and businesses also ignored warnings as far back as 1996 that climate change would bring exactly the kind of disaster they city is currently suffering today. It’s hard to blame them. We’ve all ignored the warnings.

We can’t anymore. Business leaders and politicians need to begin wrapping their heads around the big idea that climate change may mean huge financial losses in the world’s great coastal metropolises.