Global Climate Change and Cities
I likely don’t know your governor’s name, so you might not know mine: Mr. Schwarzenegger, über-body builder, actor, businessman, and celebrity politician. A Republican as well, he signed a very green bill into law last week aimed at substantially rolling back the state’s contribution to greenhouse gases, mainly via much toughened regulatory caps. In fact, he signed it twice for good measure, once in each half of the state. (Yes, it’s an election year and a big state.) This is generally considered a great thing, even by some utilities, as a way of effectively making progress on the state’s contributions to climate change.
I know what you’re thinking: That’s all well and good but what are some related urban planning research issues?
1. Kinds of problems
Cities are often blamed for contributing to the production of greenhouse gases, which are in turn often blamed for global climate change of the sort that will warm the planet enough to melt ice caps a bit, change the precipitation mix to more rain/less snow, raise sea levels, and increase the frequency of severe storms. There is an expansive literature on this set of issues (partly summarized in a new movie and book by a guy whom I believe has an appointment in my School), mainly pointing the finger at industrial pollution and cars as greenhouse gas sources. Not only are both associated with urbanization, they are differentially associated with alternative urban forms. For example, to the extent it promotes car use, sprawl is often associated with climate change.
But I don’t want to talk about the causes of climate change, about which I know least of all the many things I know nothing about. Besides, Al and Arnold are all over that. Rather, what of the consequences?
Should the planet warm with the growth of greenhouse gases, which the climate scientists I hang with claim is more a question of when than if, then cities will be, as planners are wont to say, impacted. (A fellow planning student and I saw The Deer Hunter in the 70s, perhaps the most gut-wrenching film I’d watched to that point, or since. We went to a party after and someone asked what the movie was about. Without irony, he explained that, “it was about some people impacted by the Vietnam War.” I can’t use or hear the verb since without remembering its impressive phlegmatic, flattening effect.)
Oceans will rise and storms will worsen, the consequences of which the 2005 residents of New Orleans don’t have the luxury of pondering in the abstract. That is, some cities will be affected, perhaps catastrophically. Now that’s a problem worthy of urban studies.
Which and how? How much cities have to lose from global warming depends on both their risks and their responses to those. What do we know about either?
First, it is useful to note that there is much about the dynamics of urban change, whether gradual or rapid, that is not as well understood as we’d like, ranging from the determinants and consequences of urban growth (and world urbanization trends), to the risks of cities to all kinds of hazards, to infrastructure planning and governance generally. So the context is one that starts with many research gaps.
In extreme cases, lives, property, infrastructure, public services, the private economy, and the social fabric at large are all exposed. Low-lying, flood-prone coastal cities are obviously most endangered by such trends. Other problems are more nuanced or mixed. For example, New York’s and California’s urban water supplies generally depend critically on their snow packs, which will diminish. As a different example, less snowfall and milder winters will substantially benefit many northern cities. Worldwide, tropical cities appear most at risk because of their physical circumstances, their already increasingly strained service load, and their relatively limited financial and governance abilities to roll with the punches.
Slow changes can also imply significant problems. Worsening weather and coastal conditions clearly amplify these, especially in extreme situations. In my reading, most study of the impacts of urban systems is by the transportation community, funded by the U.S.D.O.T. The first figure, from Mills and Andrey (2001), considers how more frequent and more intense weather conditions specifically with respect to transportation. It connects a list of weather hazards due to rain, heat, and wind to three transportation dimensions – facilities, their operation, and associated user demands – each having several potentially affected components.
Extreme heat or cold stress facilities, which has implications for their planning, construction, and maintenance. Climate change is expected to lead to increased frequency and severity of hot days, and fewer cold days. This could raise costs in some areas and lower them in others. Higher flood risks, and sea-level rise and storm surges in coastal areas, more clearly imply higher design, construction and maintenance costs.
“Operations” includes safety, mobility and efficiency considerations. Except under extreme storm conditions, or flooding, milder winter conditions might improve safety, all in all. Reduced spending on snow and ice control in the Midwest and Northeast could have significant savings over current levels.
How will infrastructure demand change with global warming? That is harder to say in general, but consider these scenarios:
- More resources will go into flood prevention and protection. Since the number of 100 year storms, and apparently their severity, are on the rise, the performance standards for dams, levies, sea walls and the like will probably rise substantially in coastal and near-coastal flood-plain cities, especially in developed countries with the resources to act.
- The location of public facilities, and the character of permitted private sector developments may change to either more protected or safer sites. Prohibitions on flood plain development near coasts will become more popular and perhaps better enforced where they already exist.
- On the other hand, more vulnerable sites will lose market value, all things considered. In developing countries, such sites become slum settlements for squatters. In the U.S. and other modern economies, they are the more affordable segment of the housing market. Except where housing is not permitted, this means that low income households worldwide will become even more at risk as flood risks rise.
3. Security vulnerabilities
The new School of Global Studies at Arizona State University has initiated a project looking specifically at national security issues associated with global climate change, comanaged by planning professor Subhro Guhathakurta. Which are associated specifically with cities?
If national security is defined broadly, then any event or risk that affects economic, social or political relationships is relevant. Cities are the head and shoulders of the local, regional and national economy, political, and social systems. In many cases, they are the seats of power and economy. In some of those, they are poorly positioned to mitigate climate change, sitting on coasts in tropical areas.
For example, if the Chinese Pearl River delta cities of Hong Kong, Shenzhen and Guangzhou were to suffer unexpectedly due to increased storms, even in the short term, this could threaten U.S. interests in a multitude of respects – partly by weakening the Chinese economy, and partly by the associated political instability. Many cities in India, Indonesia, Japan, and other countries face similar exposure risks.
At home, Los Angeles and New York represent a substantial share of the nation’s economic activity, while Washington D.C. houses its governance base. In the short term, these are exposed to flooding risks of the sort seen in the Gulf Coast during the Katrina disaster. While less of these cities sits below sea level, the risk of flood plain immersion is there were a storm substantial enough. Combined with other threats, such as earthquakes or overtaxed infrastructure or social services, the storm would not have to be so severe to have very costly impacts.
4. Planning options
What is the potential for adapting to significant and especially substantial impacts? Again, the transportation community has thought about this the most, as federal and state transportation agencies have funded a series of studies.
The second figure, from Potter and Savonis (2003), diagrammatically links a list of climate change impacts to different parts of the transportation planning and operations process. These include planning, project implementation, operations, and maintenance.
System planning can respond by changing the location, technology, and indeed goals of infrastructure systems. It can also reconsider land use strategies. Similarly, project development can revisit site selection, materials, and design. Operations must address performance standards under changing circumstances, and the potential for different emergency and disruptive conditions. Maintenance schedules and management may change.
The overall urban form is part of the scenario analysis, particularly to the extent that some forms raise or lessen risks of some weather hazards. That said, it is less clear whether this suggests that cities should decentralize or centralize, densify or sprawl, to a greater or lesser degree than presently. In part, we have not examined these questions in the urban literatures. In part, we have studied them badly, with limited evidence or less than credible methods.
Institutions similarly face new challenges. These include coordination problems among specialized agencies, as well as among general purpose governments with historically parochial interests. There are also scale issues, between the local and the regional especially.
In addition to changes in design and engineering-related performance standards in construction and maintenance, the primary challenge is that of changing behaviors to reduce vulnerability to emerging hazards. Education is part of the mix, as is improvements in communication systems. But moving people away from vulnerable areas is a long-standing and always thorny problem, that involves market forces, property rights, and evaluations of private versus public interests that are less than straightforward to resolve.
5. Research Challenges
What is perhaps clearest about our understanding of what the risks are to cities, their residents, and their facilities, is how thin our knowledge – and thus, possibly, our preparation and prevention plans – is. These range from the challenge of better understanding how urban form affects service provision, to the hydrology of climate change, to changes in demand by place and time, and so on.
Figure 3, cobbled together from several tables in Potter (2002), lists a dozen along with more specific product requirements.
So, while there is much to learn, there are also substantial risks to evaluate. The short term risks have more to do with the expected increased frequency and severity of weather conditions than with sea level rises, or gradual warming as such. While Katrina may have nothing to do with global climate change, it is indeed reflects the sort of global warming-induced disaster that better planning could address.
How to do so, regarding either urban infrastructure performance, the location and character of urban development, or the governance process, is less clear, as are the relative merits (cost/benefits) of alternative means and mechanisms. If not exactly the kind of Russian roulette played in The Deer Hunter, purely for desperate thrills, planning for global climate change does call for a calculated response to unpredictable yet more likely calamitous events. We have work to do on those calculations.
McBean, G. and D. Henstra (2003) “Climate change, natural hazards and cities,” Natural Resources Canada, ICLR Paper No. 31
Mills, B. and J. Andrey (2002) “Climate change and transportation: Potential interactions and impacts,” Volpe Center, U.S.D.O.T.
Potter, J. (2002) “The potential impacts of climate change on transportation: Workshop Summary, Volpe Center, U.S.D.O.T.
Potter, J. and M. Savonis (2003) “Transportation in an age of climate change: What are the research priorities?” TR News 227, July-August.
Zimmerman, R. (2002) “Global climate change and transportation infrastructure: Lessons from the New York area,” Volpe Center, U.S.D.O.T.
- Monday, October 2nd, 2006
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