For most of human history, extreme climate events punctuated otherwise placid background conditions, with such impressive force or consequence that they were ascribed to the anger or vicissitudes of the gods (in fact, it could be argued that their existence spurred the need for explanatory supernatural beings in the first place). From droughts triggering uprisings in ancient Egypt to the sinking of the Spanish Armada to the extreme cold that thwarted multiple Russian invasions, extreme events not only strongly shaped contemporary happenings, but cast a long shadow that in some cases continues through to the present. In spite of this complexity of historical effects, the relationship was always unidirectional: climate affecting people.
It's only in the 20th and 21st centuries that humans have begun to meaningfully affect the climate, introducing a new kind of complexity. This is often cited as a compelling reason for avoiding (or at least extremely carefully implementing) geoengineering — in addition to its unpredictable effects and the shifting political foundation that such efforts would rely on, there's an additional moral complication when a purposeful act results in a catastrophe. Suppose a devastating drought or storm could be traced to a geoengineering plan; could it be argued that the designers, funders, or technicians associated with the plan should be held responsible, that they should have known? A precedent about scientific foreknowledge (albeit a much-criticized one) was set in the infamous trial of Italian seismologists in connection with the deadly L'Aquila earthquake of 2009. The moral implications of 'natural' versus 'anthropogenic' (and whether such a distinction even makes sense anymore) are explored in a thought-provoking book by Bill Gail. Overall, doing something is at its very core viewed through a different moral lens than doing nothing (witness the famous runaway-trolley thought experiment), just as doing something purposefully is different than doing something accidentally. The lens one uses to approach anthropogenic climate change therefore greatly affects the takeaways of who's responsible and what's the optimal future course of action.
Like most problems related to human civilization, environmental or otherwise, the challenge of adaptation to extreme climate events is multiplied by the number of people affected. Gathering the resources to support millions of people in need in the aftermath of a disaster remains difficult for even the most advanced societies, and often solutions involve more of the thing that caused the problem in the first place. An exemplar of both categories is air conditioning, as shown in the figure above. Invented for machines (not people), it has come to be the quintessential emblem of a comfortable lifestyle, in high demand across the world. These multiplying devices in a warming climate will themselves lead to so much energy demand as to cause an additional 0.5 C of warming by 2100. While that report is optimistic about the cost competitiveness of technical advances that would neutralize the negative effects of a 5x increase in A/C demand over the 21st century, others are not as sanguine. But from a moral perspective, how can something be used (to excess) by some groups of people and then denied to others? Even if we now know the externalities associated with e.g. cheap coal-fired electricity, it is not straightforward to argue that this means Indonesia's people in 2019 should be forced to use more difficult or expensive sources of energy than those that powered Britain's Industrial Revolution 10 generations prior. Clearly it is desirable to make efforts to enable economic growth and environmental protection to be compatible, but in cases where they truly conflict, that's where the moral questions are most pronounced.
Extremes, anthropogenic global warming, and geographic patterns of development all come to a head in urban climatology. In most cases (that is, in non-centrally-planned economies), people move to cities of their own free will, in order to pursue economic or cultural opportunities unavailable in smaller places. From a utilitarian standpoint, this is unquestionably good. From a climate standpoint, cities tend to amplify the challenges of extremes (particularly in a warming world), with the classic example being urban heat islands. The cost of an event, as well as the event itself, is often increased when occurring in an urban setting.
On the other hand, both extremes and cities' effects on them have certain advantages. For instance, consider extreme cold (the kind that is currently enveloping the Midwest in a once-in-a-generation chill). The urban heat island aids in mitigating extreme cold, non-negligibly reducing its associated mortality and economic effects. This would seem to impose a kind of conditional goodness on urban warming that's a direct function of the ambient temperature. Yet it's not so simple as to say that extremes are 'bad' and moderate conditions 'good' (though one can't help but have a positive emotional reaction when reading about increasingly mild weather). Cold extremes help hold pests in check, while wet extremes are often useful in recovering from severe long-term droughts. Even if we had the knowledge and power to turn one knob to reduce some extreme, should we? And who would do it? And what would be the criteria they would use to decide? And what if something went wrong? The political, legal, and philosophical quandaries are endless, to say nothing of the scientific and technical ones. And yet, on the other hand, we are already engaged in a vast centuries-long unplanned experiment. No handbook on climate etiquette yet exists, though maybe we should be thinking along those lines, as individuals as well as governments, businesses, and other organizations.
Furthermore, looking to a future where extremes and their effects generally grow larger and larger in a warmer world with more severe drought and floods, these questions become more urgent. As described above, they involve time-lagged inequality, the human-environment relationship, and the complex interacting effects of climate extremes. Certain of these aspects fall under the umbrella of 'climate justice', the recent movement to more explicitly consider the socioeconomic and cultural dimensions of environmental problems, and consequently press for socioeconomic and cultural types of solutions. Others are more complex. Regardless, new ways of thinking about climatic-anthropogenic feedbacks are necessary in a time when our power to shape the global climate is larger than ever before, so large in effect that not only our actions, but the externalities of our actions, strongly affect societies, economies, and ecosystems the world over. I am hopeful that the more we reflect on this moral problem, the more likely it is that we will come to solutions (at least, piecemeal ones) that mitigate the complexities our civilizational developments have brought into being.
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.