Last week I attended a panel on extreme heat, which like many recent events had the seemingly mandatory mix of representatives from the four corners of science/applied science -- government, nonprofit, business, and academia. While this attempt at interdisciplinarity is often more like the sound of many voices speaking rather than a choir singing, it does reveal certain aspects of scientific problems that have not traditionally been appreciated, and suggest certain solutions to them. The large attendance that these events often attract is a testament to this value in this regard.
Heat has long been a serious but underestimated threat. Multiple stories on the topic are included in WNYC's "Harlem Heat Project", among other notable public-facing science efforts. Heat is not like tornadoes or hurricanes, which come in with obvious force and create indelible images of destruction; it's a silent killer, striking people in their homes, often in cities, almost occurring right under the noses of doctors, researchers, and civic organizations. Vulnerability to extreme heat has dropped significantly over the past century, with the spread of electricity and (most importantly) air conditioning, but it remains the single biggest source of weather-related mortality in the US -- in NYC, it averages about 100 deaths per year according to the city health department. The panelists agreed that to a certain extent this is the result of a messaging problem: warnings about heat often are illustrated with people exercising or working outdoors, while in fact the majority of heat-related deaths occur indoors, to sedentary people already in poor health.
Cities are a danger zone for extreme heat, particularly looking toward the future. Outdoor temperatures in cities are hotter than elsewhere by up to 10 F due to the urban heat island, and urban residents tend to spend significant time exposed to these conditions, whether working, commuting, or doing errands. On top of this, poor airflow in cramped spaces of the urban landscape results in pockets of heat that can be severe. For example, underground subway station platforms in New York City are stiflingly hot in the summer. Small apartments, in buildings packed close together, heat up at the beginning of a heat wave and don't cool down (day or night) until it's over (see figure below). With such conditions, it's fun to imagine powerful but unorthodox solutions, such as agriculturally inspired 'heat fans' on the Hudson to help alleviate heat trapped in the canyons of Midtown.
In contrast, current attempts to remedy the issue are generally incremental and woefully inadequate, and (by the city's own admission) usually do not reflect 'best practices'. For instance, the advertised network of official cooling centers consists of voluntarily offered spaces whose availability fluctuates from season to season, are non-uniformly distributed, and are unattractive for spending significant amounts of time. Needless to say, this putative resource is heavily underutilized. Part of the problem is societal and universal -- the desire to 'hunker down', even in the face of an imminent, obvious, and instinctual threat like a hurricane. Thus, a significant fraction of people don't want to spend money on something they consider a luxury rather than a necessity. There is also the age-old trope that issues affecting the poor or otherwise disenfranchised attract less attention and funding, from the private and public sectors alike.
Looking forward, proposals the panelists mentioned included policy solutions (e.g. mandating cooling rooms in all new buildings), technological solutions (e.g. health-monitoring devices), and social solutions (e.g. encouraging cohesion among building residents). Improving messaging about who heat's victims really are could make a big dent in the problem also. Much of the implementation challenge is governance: city agencies don't coordinate their efforts, resulting in a struggle to get funding even for projects that would save money in multiple ways (e.g. reducing subway heat would also reduce taxpayer-funded medical treatment for heat exhaustion); and city, state, and federal governments often work at cross-purposes, or with incomplete information.
As global-mean warming continues, baselines are shifting so rapidly that (as one panelist said) we almost expect extremes now, at least as defined relative to the 30-year retrospective temperature distribution. Together with increasing knowledge of the wide-ranging impacts of climate extremes, and how these impacts cascade through many realms of society, this motivates calls for what could be called a 'new environmental ethics' -- that is, broad awareness of the causes and externalities associated with extreme heat and pushes for creative ways of solving them. For example, one such solution could involve discounts for reducing personal vulnerability, much like health insurers already give discounts for gym memberships and other healthy activities. A carbon tax on energy producers is another clear candidate. With these kinds of market failures properly addressed, it would not be long before more creative approaches come along in the urban planning, public health, communications, and policy realms, spurred on by the incentive to improve lives and make our societies more resilient to extreme heat overall.
Our research group wrote an opinion article that was published today in the New York Times. It summarizes Ethan Coffel's recent study showing that heat-humidity combinations so extreme that even constant sweat won't be able to sufficiently cool us down will become a reality and then a regularity by 2080 in parts of the tropics and subtropics, many of them densely populated and all of them having contributed relatively little to cumulative greenhouse-gas emissions. The rest of the world will also see sharp increases in extreme humid heat, and the resulting heat stress. Although these projections are for the late 21st century and RCP8.5, what's considered the 'worst-case' trajectory (with warming of 3.0-4.5 deg C since the 19th century), that's exactly the trajectory that the world has been on ever since the first IPCC Assessment Report in 1990. Glimmers of meaningful changes are happening, but there's still a long way to go before global emissions begin to decelerate -- and then level out -- and then drop. All the while, concentrations of greenhouse gases in the atmosphere will continue to rise.
In a long-term sense, then, the just-released IPCC report on climate changes for 1.5 deg C of warming vs 2.0 deg C is good for awareness but mostly an exercise in rearranging the deck chairs on the Titanic. In all likelihood, we'll blow by both of those targets within 30 years. Among many other things, that means there'll be a continuing need for evaluating the effects of this ever-increasing heat on health, the economy (e.g. agriculture, natural resources, tourism), and ecosystems. It would be great if this article, with its focus on awareness of the risks and its faint policy recommendations, were the last of its kind, but many more such articles will probably be necessary. Being the bearer of bad news is not a pleasure so much as a service. As a climate scientist, I got into this business because I enjoy understanding the intricate patterns, and in the absence of anthropogenic climate change there would still be plenty to study -- understanding natural variability, advancing high-resolution modeling, working on seamlessly merging climate and weather prediction. That's the positive message I try to convey when discussing my work, but that's not to make light of the very real risks that the most hard-edged aspects of climate change, such as extreme humid heat, will pose to lives, property, and livelihoods around the world.
I recently attended the International Conference on Urban Climate, which, quite appropriately for an event whose major themes include megacities and hot weather, was held in New York during a typically grueling August heat wave. Among the ideas and findings were a number of demonstrations of emerging research tools. Some of them represent technological breakthroughs, others approaches applied in new and innovative ways. A selection of the most exciting are highlighted in the following paragraphs.
As more and more money is poured into (re)designing urban areas in ways that are climate-aware, how do we ensure that this money is well-spent? For example, a common strategy is to plant more street trees, but how many and where? The usual approaches, in increasing order of accuracy and price, involve expert judgment; a few field experiments, extrapolated to the entire city; or a series of climate-model runs differing only in the surface land cover. A way to get accuracy much more easily is to employ an algorithm that can quickly run through possibilities and select the optimum. Kunihiko Fujiwara from Takenaka Corporation discussed just such an algorithm, aimed at designing an optimal Tree Arrangement Priority map for a city. This means iterating through the steps of tree arrangement, calculation of surrounding temperatures, determination of the cost-effectiveness of the tree, and finally back to slightly modifying the tree arrangement to see if the cost-effectiveness improves.
Tianzhen Hong from Lawrence Berkeley National Lab talked about his group's development of a new feature for the EnergyPlus software program which makes it possible to simulate energy demand of every building in a city at 10-minute intervals. To do this accurately, they must take into account its occupancy, materials, geometry, and neighbors, as well as the ambient weather conditions. The underlying platform, City Building Energy Saver, allows free analysis of neighborhoods in several US cities, both as they are and with potential modifications. This tool fills an important niche, as the interactions between adjoining buildings, neighborhoods, and even cities as a whole are drawing more attention (for example, a keynote by Marshall Shepherd discussed the nascent concept of ‘urban archipelagos’, a term implying that in some areas each island affects and is affected by the others nearby).
Field campaigns are endangered. At least, that’s the sense I got from hearing several people discuss the Digital Synthetic Cities approach. A leading proponent of it is Dan Aliaga at Purdue, although it has more and more practitioners. The essential idea is to create a digital model of a city that has the same properties as a real one – the same building sizes and materials, the same thermal properties of the streets and vegetation, the same solar-radiation input – but which only exists in digital space, making it easier to study. The verisimilitude gives it a slightly uncanny movie-like or video-game-like quality, not too different from Seahaven Island in The Truman Show. Of course, creating synthetic data or a synthetic environment is nothing new, and is happening across disciplines. This speaks to the power and universality of statistics – at their core, statistics are exactly designed to serve as a layer of abstraction, to describe things such that the actual thing is no longer needed. The novelty is in the complexity and concomitant power of these digital synthetic cities to answer questions that were previously well beyond the range of feasible computation, such as understanding the causes of small-scale precipitation patterns in a particular storm. The advances this approach will bring include a newfound ability to examine details of a certain location's climate, but also to better generalize findings as new patterns are uncovered and new processes are simulated, making it easier than ever to not only say why Place A and Place B are different, but why they are similar.
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.