Just as rising global temperatures will accelerate change in ecological systems, a 4° Celsius world will catalyze social changes in the United States. In some parts of the country, these changes will include greater need for rapid emergency responses, heavier reliance on healthcare systems, and obsolescence and emergence of industries. In other parts, they will include the need to accommodate population influxes and a greater draw on social services. Though it is impossible to generalize regarding what life in four-degree cities will be like, it is clear that such a world will require different local responses, of different magnitudes, than we see currently. Some of the questions that this level of warming will raise are: What must a city give up in a world of four degrees warming? What should it be unwilling to lose? And how might it need to transform?

Many cities will lose both land and people in a four-degree world. Contemplating that first loss, land, is likely to feel sacrilegious to many cities. There are currently few incentives, and many disincentives, for a city to shrink its square footage. Property taxes are generally the primary funding mechanisms available to local governments. That tax base, tied so explicitly to land and what is on it, means that a loss of property equals a loss of revenue. But a four-degree world will render large parts of many cities unlivable and will require dramatic reconfigurations of others. Many cities will experience the loss of land beset by flooding, fire, drought, or other destructive forces. Even if these disasters do not result in the total destruction of the land, they may well alter its usability and the buildings—and taxpayers—upon it.

Those realities mean that many cities will lose some of their property tax base. It also means that cities will be forced to choose what to protect and what to abandon. Historic sites, cultural objects, and landmarks may need to be abandoned in favor of investing resources to protect people who used to live in the city and those who may remain. Because along with the land and property, population loss will be an inevitable part of a four-degree future in some places. There is no amount of adaptation that will be sufficient to keep current population levels in place in many cities, particularly those in coastal areas vulnerable to sea-level rise or located in the West, where water resources will be increasingly scarce and temperatures increasingly ill-suited for human habitation. Thus, cities will have to contend with the loss of people, with successful out-migration as a best-case scenario, and loss of life to flooding, heat, and fire a real prospect as well.

Those losses are enormous. They will feel enormous. But to confront them in a clear-eyed way, cities will need to face the question of what they can provide in a four-degree future and what they must retain so they can fulfill their new roles. Cities will still exist, likely in even larger form as climate change is expected to fuel massive urbanization. And the COVID-19 pandemic has illuminated the vital role of cities as places where people gather and seek aid. This has long been the role of cities, and they will continue as important intersections of public and private space. Cities can and should also retain the ability to be a locus for expression of local opinions, needs, and culture. A four-degree world will impact communities in distinct ways.

As the level of government closest to the ground, cities can play a role in responding to shifting and varied needs. To fulfill those roles, however, however, cities must retain local authority. For example, at different points during the COVID-19 pandemic, local entities such as cities and school districts have attempted to combat local spread by implementing mask mandates and other public health measures. In some cases, state legislatures have reacted by prohibiting local governments from taking such actions. This dynamic strips away an important layer of crisis responsiveness, and makes very difficult for local entities to respond to the health and safety needs of their citizens and constituents.

There will be times when local authority is exercised in ways that run counter to the best science and policy on climate change. For example, local governments in many states have created barriers to renewable energy facilities being sited within their boundaries. Local governments have economic and political incentives to promote development in coastal areas vulnerable to sea level rise and flooding. And parochial actions at the local level have long been used to limit available housing stock, as well as to drive gentrification; it would not be surprising to see similar trends in climate destination cities when larger population shifts start occurring. A call for protecting the capacity for local action in reponse to climate change does not and cannot guarantee the shape of those actions. But even with some inevitably undesirable local actions, experience has shown that cities are often on the front lines of climate planning and, depending on the politics of the moment, may be the only entity in the federal system willing to take action. Beyond that, they are the entities most likely to know and understand the needs of their citizens in a rapidly changing environment, and they are going to need to respond to large swings in population, public health needs, natural disasters, and more. The federal government and the states must play an outsized role in making the regulatory and structural changes a four-degree future will require, and can exercise their authority to set regulatory floors for local government climate response. It would be a mistake, however,to fully strip authority from local governments to act.

So what needs to change to allow four-degree cities to fill the roles required of them? There are of course as many answers as there are local governments. All, however, are likely to center on some version of flexibility. Every city will need a greater ability—and, perhaps, a new willingness—to understand and interpret climate data and to use that data in planning for the future. In doing that planning, both physical and policy agility will be hugely important. Physically, cities must recognize when they are entering infrastructure time horizons that no longer make sense; having the foresight to avoid committing funds and locking in obsolete physical patterns (such as water lines in flood-prone areas, new development unsupported by available water resources, massive infrastructure aimed at serving shrinking populations, and others) will be crucial for city survival. Cities must also be willing to reimagine planning documents to account for new physical realities and changing demographics.

On the policy side, cities must be nimble enough to adjust to the needs of their citizens and willing to engage with those needs without being too wedded to the past. Depending on the city, that may mean managing water rationing, adapting the housing supply, making decisions about whether or not to rebuild in areas impacted by natural disaster, providing health and disaster response services, joining forces with other cities for service provision, and on and on. All of that will require the four-degree city to have greater flexibility in financing and in collaborating with other jurisdictions. As described above, local governments cannot afford to lose this authority over climate responsiveness, and many may in fact need to acquire that authority in the first instance. Broadly speaking, this flexibility and autonomy are something that can only be—and, where it is lacking, should be—conveyed by the state. The prospect of a four-degree future, and the limited capacities of all levels of government, should serve as an impetus for a more expansive idea of local authority. States could ensure local flexibility by, for example, reforming available local revenue sources, allowing for and encouraging regional planning around climate impacts, and at a very broad level, putting in place forms of home rule authority that presume local ability to act and move away from deregulatory preemption. Cities in a four-degree world will have much to contend with; one thing they should not have to worry about is the authority to act.

The four-degree city is likely to be similar in mission to current cities, but will perhaps have a very different footprint and make-up. Current local government structures, including financing mechanisms, policy incentives, limited authority, and entrenched commitments, make it extremely difficult to accommodate this coming reality. Now is the time for cities, states, and the federal government to ensure that cities that will be impacted by climate change (read: all of them) have the authority and flexibility they need to prepare for a four-degree future.

Authored by:

  • Sarah Fox, Associate Professor of Law, Northern Illinois University College of Law.

*** This blog post is part of a series of essays by the Environmental Law Collaborative (ELC) on the adaptation challenges of the worst-case climate scenario: a world that warms to 4°C by 2100.
Pace | Haub Environmental Law’s GreenLawBlog is co-hosting this series, along with Environmental Law Prof Blog, over the course of this month. ***