A large part of applied urban climatology consists of identifying climate-related hazards for existing urban areas, and devising solutions that either mitigate the problem (“mitigation”) or increase the community’s ability to cope with it (“adaptation”). Rarely, however, do we take the evaluation back to its natural starting point — that is, the location and form of urban areas in the first place. Perhaps this is because the major aspects of cities like size and location are largely outside the control of any one generation of policymakers, so that they are essentially unchangeable, especially on the approximately decadal timescales that are relevant for most climate planning. This unchanging character means a substantial amount of lock-in of future emissions due to the development patterns that exist today (that is, future emissions even if all future development was planned to be perfectly carbon-neutral). This concept could perhaps be extended to include locked-in societal risks as well. Unfortunately, the price tag and level of political wherewithal necessary to meaningfully change these patterns are all but unachievable. In certain ways, this is a positive: strong-arming people into relocating to places of the government’s choosing, even if those places are objectively identified, does not seem palatable. What is more feasible is preventing or disincentivizing additional high-risk development, rather than attempting a post hoc ‘cure’ for poorly planned cities. As with most prevention/cure dichotomies, prevention is much easier — and given that the costs of these decisions are ultimately manifest on a societal level when they balloon to a certain size, these choices should be of interest to all.
There are several levels of bad decisions about choosing the location for a city or other new development. There are the harmless mistakes (siting Lima in the summer, not knowing about the constantly cloudy winters), the constrictions that become apparent only as a city grows to appreciable size (water availability in Cape Town), and the constrictions that should have been apparent from the very start (the smidgen of naturally high ground in New Orleans). Of course, the recent troubles with the above-mentioned places could largely have been avoided with better long-term planning, and responsibility for the crises of Hurricane Katrina and the 2016-18 Cape Town water shortage should not rest solely on the shoulders of the cities’ founders. After all, in many such cases it took centuries for the problems to reach levels where they could cause a significant negative impact on daily life. Modern-day development that expands cities, however, cannot so easily claim ignorance. Paving large sections of the Texas Gulf Coast, or building homes in claustrophobic California canyons, is enabled by the absence of open-market forces (e.g. lower-than-fair insurance premiums) in combination with a propensity to underestimate the associated risks. Harveys and wildfires, in other words, were not sufficiently considered or prepared for. Some meetings I attended last fall focused on the rapid population growth of the ‘wildland-urban interface’ and the tragedy-of-the-commons hazards and public-services demands that it raises. And that’s in the comparatively data- and resource-rich United States. Whether in the hills of Nepal or the floodplains of Nigeria, urban sprawl still proceeds largely unchecked in most of the developing world, with little consideration for or knowledge of the eventual societal-level costs when these homes are damaged or destroyed (and many of them are highly vulnerable, even in the absence of anthropogenic climate change). In these places, the residents are left destitute if climate-related disaster strikes, even if the strike is fairly routine or predictable; in the developed world, residents are financially saved but typically only by the failsafe backstop of the government, and thus any kind of development with a non-negligible chance of falling into this category is really a public concern. As with many of the most interesting aspects of urban climatology, this is where science and policy blur together indistinguishably.
On the policy side, the principal question revolves around how to appropriately incentivize development that's aware of the risks and vulnerabilities imposed by its location. A commonly voiced but as-yet-undone step in this direction would be to reform government-run mortgage and insurance programs to increase the financial penalty for developing areas that are known to be high-risk. Multiple overlapping evaluations of potential environmental consequences at scales from individual homes to metropolitan areas would also be wise, particularly in cases where problems may only emerge for certain types or densities of development. These could consider multiple development options at the neighborhood scale in combination with a simple climate simulation to address questions like, for instance, whether the overall risks of flooding along a beachfront are smaller with several apartment towers or a large number of homes. Detailed climate information could be used for analysis if local high-resolution simulations are unavailable or prohibitive. Of course, historically and straight through to the present, it has often been the case that the residents of high-risk areas were forced there by circumstance and would leave if they could; this represents another necessary dimension of any comprehensive policy solution. In other words, smart development requires a true proactive dialogue among actors before major urban-planning (development, zoning, etc) decisions are made. While urban-climate tools are rapidly gaining in their usefulness for analyzing the effects of past development, it would be even more gratifying to use them strategically to help guide these kinds of choices in the first place.