A 2006 image from NOAA GOES/NASA-Goddard Space Flight Center

This column was first published by the Washington Post and re-published here with the authors’ permission.

Hundred-year floods. Record-breaking Antarctic heat. Wildfires and drought. The stories appear with numbing regularity. And though the details differ, they all point to the same grim conclusion. We’re failing to address climate change. With carbon emissions continuing to rise, what were once dismissed as worst-case scenarios now look like the best we can hope for.

If Plan A was to prevent, or at least mitigate, the most serious impacts of climate change, what’s Plan B?

In our Plan-A world, architecture and planning has become focused on the idea of “resilient” design. But continuing to talk about “resilience” in the face of ever-worsening projections is its own form of climate denial. It’s time for planners to begin replacing the R-word of the moment with a now not-so-unthinkable one.

Retreat.

According to a recent paper in the scientific journal Nature Communications, some of the earlier projections of population displacement from sea-level rise are probably way too low. Around the world, instead of some 50 million people being forced to move to higher ground over the next 30 years, the oceans will likely rise higher than predicted, with a coastal diaspora at least three times larger; by 2100, the number of climate refugees could surpass 300 million. Indeed, sea-level rise looks likely to be measured in yards and meters, not inches or feet.

Where will all of these displaced people go? Can they be accommodated in existing cities, towns and villages? Which cities will we defend? Which will we surrender? Who will decide? These are unprecedented design and planning challenges that our society hasn’t begun to think about, let alone plan for. Given the increasingly dire outlook, we believe it is time to start.

We must continue to wage the political fight to rein in and eventually eliminate fossil fuels, while at the same time remaining clear-eyed about what needs to happen should our best efforts fail.

In recent years, we’ve seen countless climate-resiliency schemes featuring bioswales, rain gardens, retention ponds, earth berms, levees, sea-wall barriers, even oyster beds. All of these strategies are useful, but they come with a big “if.” They will help protect our coastal cities if we also cut our carbon emissions in time to mitigate even worse impacts of climate change.

Both of us live in New Orleans, a city that is below sea level but that is not at all inclined to give up. But for the sake of future generations, we need to honestly assess the threats ahead and plan accordingly. Planners are expected to operate within multiple time frames, and the challenge today is even trickier. We must continue to wage the political fight to rein in and eventually eliminate fossil fuels, while at the same time remaining clear-eyed about what needs to happen should our best efforts fail. Doing both is the only responsible course of action.

It is not overly alarmist to start thinking about exit strategies that work under the most severe scenarios. Moving existing cities, retrofitting old ones for explosive growth, creating new settlements and mitigating thousands of miles of polluted shorelines will be expensive and complicated. Even if properly planned, this will be a messy and even brutal process; if unplanned and ad hoc, in all likelihood, it will descend into a chaos straight out of science fiction.

Steven’s firm, Concordia, led the politically and emotionally charged planning process in post-Katrina New Orleans, a city with a pre-storm population of 485,000. (Today, that number stands at about 390,000.) That was certainly a difficult and unprecedented effort, but it was nothing compared to the simultaneous challenges facing coastal towns and cities in the decades ahead. And our problems don’t stop at the water’s edge. Many places inland will see water become increasingly scarce, putting immense stress on settlement patterns and agriculture. Mass migrations will inevitably become a part of our children’s and grandchildren’s futures.

Sadly, few of our politicians will “go there” yet, because their planning for the future extends precisely as far as the next election. It’s time for architects and planners to sound the alarm. Time, in other words, to get real.

The irony is that as we dawdle, energy and insurance companies, along with the Pentagon, are turning to face what’s coming. In the real world, that’s called risk management. And while many cities have begun the process of resilient planning, it is time for them to join with states and regions, as well as the civilian side of federal government, to be sure the unavoidable disruptions are anticipated and managed as humanely and fairly as possible.

An inundated coastline is not just a national security issue; it’s not just an actuarial challenge for the insurance industry. It’s our future, and it’s upon us.

Steven Bingler is a New Orleans-based architect and planner and founder of Common Edge Collaborative, a nonprofit organization that advocates planning and design engagement with the public. Martin C. Pedersen is executive director of the organization and the chairman of The Lens’ board of directors.