Making yourself scarce is in vogue — identifying and reducing carbon footprints, leaving no trace when visiting parks, restoring various natural environments, etc. This trend is in response to a long history of conspicuous consumption and attendant environmental damages. The imperative of economic development results in most every country having a clear pattern emerge as the arc of development progresses: build {buildings, infrastructure, industries, wealth} first, consider the consequences later. This applies equally to lives (safety regulations) and finances (consumer protections) as it does to the environment. Then, as people get more stuff, they get more conservative and have a greater desire to protect what they have versus acquiring even more. In Europe & North America, the development pendulum began swinging back from indiscriminate and cheap to expensive and more-carefully-considered around the third quarter of the 20th century, and there is some indication that it’s begun swinging back in places like China as well (somewhat ahead of expectations), but it’s still on its initial ramp-up in places like Sub-Saharan Africa and South Asia. In a sense, then, environmentalism in the real world is discretionary – desirable to everyone, but always decidedly in a mediocre position (at best) in the public’s list of priorities. As the environment improves, as it has in the US since the mid-20th century (whose unprecedented pollution and unfettered industrial activities prompted the first major environmental movement), the marginal value of additional investment and attention decreases. Concern for 'naturalness' has come in multiple waves, though, and it's interesting to note that the animating conservationist spirit of the 19th century in fact preceded large-scale industrialization, and how the modern emphasis on clean air, water, etc. is echoed in the ethos of that era, despite the interlude of a century of faith in the all-curative power of technology to liberate people from their surroundings. Whatever the exact reason, there is now a growing awareness of more-nuanced effects than burning rivers and black smog -- things like cardiac stress from increased heat, economic impacts of heat extremes (plus another paper on heat extremes), and greater infant mortality from air pollution. Below are three examples of cities that are experimenting with different ways of consciously shaping their urban form to reduce its impact on the surrounding environment, with the aim of making their economies stronger and citizens healthier. In essence, all three are bargaining that -- given the costs of environmental degradation -- doing something is not only morally preferable but in fact cheaper in the long run than doing nothing. In Los Angeles, concern centers on the effect of the urban heat island on human health. Scientists working with city planners are aiming to reduce extreme summertime heat by 1.5 deg K by 2040, which is comparable with the projected increase in temperature in the same timespan. There are theoretically well-founded methods of doing this -- whitening roofs, planting more vegetation, rounding off building corners to facilitate airflow -- but the sheer quantity and variety of built structures across Southern California, combined with the region's many microclimates, make it an especially challenging task. New technology, such as permeable and/or more-reflective asphalt, may come into play. The exact cooling strategy will likely differ from neighborhood to neighborhood, based on the current situation. For example, a canyon already has sufficient airflow, but a mid-valley spot may not; reflective asphalt will be less effective in an area where the streets are already shady. There is also the inherent push-pull between water conservation and temperature limitation, because water (via evaporative cooling) is the single most effective way to cool the air. And of course Los Angeles has a particularly tangled history with using water from other places for its own purposes. With the attendant complications, overcoming financial, technical, climatological, and political obstacles to reach the city's goal will be a demonstration of the feasibility of this cooling program just about anywhere that has the resources to invest in itself in this upfront manner, and that then need only watch the dividends slowly accrue over the following decades. In Barcelona, the aim is cultural as much as it is climatological. With the vision of recreating the vibrant pedestrian-oriented urban patchwork that was ubiquitous before motor vehicles came to dominate just about every block across the globe (not to mention the reshaping of cities to their specifications), streets in parts of the city are being eliminated to form 'superblocks' -- nearly-carless cities-within-cities. Public opinion is conflicted, naturally, but transportation officials are adamant that the idea is a net positive, in terms of traffic pollution as well as noise reduction, space for play, and more social interactions. These positives seem quite straightforward. But part of the trouble is that while Barcelona is known for its compactness, that same factor also restricts airflow, magnifying the effect of whatever traffic pollution there is. Further, there is the traffic-engineering maxim of 'latent demand', which posits that traffic will always swell to fill whatever space you allot it -- and by not banning traffic altogether (which would be very difficult indeed), critics fear the creation of traffic-choked boulevards that are disruptive but no improvement over distributed side streets. Lastly, there are concerns about accessibility, longer commutes, etc. that have yet to be fully addressed. In any case, if the experiment is deemed a success it is sure to be replicated many times over elsewhere, providing a new template for modern urban design.
And in New York, plans rely primarily on vegetation and its ability to cool the surrounding air by evapotranspiration as well as through direct shading of the surface. Some roof-whitening is also in the mix. There is an unmistakable socioeconomic dimension to this program, given the strong correlation between vegetation cover and household income that is present in New York as it is in most other cities. This correlation is compounded by another one, that between air conditioning and knowledge of/access to social & medical services on the one hand, and household income on the other. City officials have some additional metrics with which to decide how to direct their investment: the economic benefits of existing trees, in terms of stormwater interception, energy conservation (through cooling from shading and evapotranspiration), air-pollution reduction, and CO2 absorption, have been calculated and mapped (using US Forest Service formulas) for every street tree in the entire city. Then, weather observations can show the hottest areas, and, in combination with climate and tree-benefit models, allow precise estimates of the efficacy of placing trees and/or white roofs on a given city block, ultimately yielding a ranked list of the most-cost-effective sites. While there are other issues for which income and climate vulnerability are closely linked, in New York as elsewhere, addressing the longstanding problem of urban heat is certainly a defensible place to start.
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Using the algorithm I developed that's described on the Recent Weather page (and which I applied to the United States in an earlier post), here I extend the analysis globally using a gridded reanalysis product (NCEP). This data is a combination of all available stations, standardized to remove known effects like urban heat islands, and is produced at 6-hourly intervals. The algorithm I'm using computes comfort as a function of the heat index (if hot) or the wind chill (if cold), with the ideal conditions defined as being between 70 and 80 F, 24 hours a day. Notably, precipitation is not included -- though it may be in future iterations.
Doing this computation for world metropolitan areas with more than 2.5 million people (first figure below; click at top left to select a month to view) reveals some clear patterns. First and foremost, cities in the tropics (i.e. with nearly constant temperatures) at moderate elevations (i.e. are cooler than sea level) are comfortable all year long. This makes many of the South American cities rank very favorably. Spring in East Asia is pleasant (it's still relatively cool in North America and Europe), with nice summers particularly in coastal West Africa, then East Asia and Italy make appearances in autumn. Boston (July and August) is the only US city on the list, keeping San Diego from the stage in those months. November and December are omitted due to map limits, but are similar to March and February respectively. I also calculated the least-comfortable cities, though I don't show the map here; given the lack of large cities in the cold parts of the Southern Hemisphere, this list is studded with cold cities in boreal winter (Russia, northern China, and Canada) and then from spring through fall flips to tropical cities experiencing their dry season (e.g. India, West Africa) alongside perennially hot and moist areas (Indonesia, Singapore).
Then, I was interested in the question: given a particular location, when's the best time to visit it, according to this algorithm? Below is a first stab at an answer. In the map, reds and purples represent areas that are most comfortable in boreal winter (December-January-February) and greens represent areas that are most comfortable in boreal summer (June-July-August). Broadly speaking, the patterns track the warmest month in cool climates and the coolest month in warm climates. Note that this means cool ocean areas track SSTs and show up as September or October in the Northern Hemisphere, but this is interestingly not the case in the Southern Hemisphere. I speculate this characteristic may be related to the significantly stronger wind speed in the SH resulting in lower wind chills over the ocean during boreal-autumn storms, even if the SSTs are warmest then.
Because the map is based on a 2.5x2.5-degree grid, fine spatial details are not resolved. Nonetheless, one can still pick out regional features like the warmth of the Northeast-US corridor relative to inland (October vs August/September); the cool post-monsoon climate of southwest India; the island of cooler air over the Alps; the month-by-month progress of clear latitudinal bands of comfort stretching across Australia; and the dryness of western China relative to eastern, which results in the former being most comfortable in mid-summer while the latter is so in mid-spring and mid-fall. The data being of better quality than that of Mieczkowski 1985, and the algorithm more precise, in my view these results are a refinement of his work, and yet agree well with his "tourism climatic index" for January. While humans are capable of adapting to any climate, this comfort analysis is designed to reflect the ease of living in a particular location, climatologically speaking. It thus also is an index of the amount of energy needed to maintain equable indoor temperatures -- a place like Saudi Arabia, where 60% of summertime energy consumption goes toward air conditioning, clearly does not rank high on this list. With more and more of us on the planet, and continual discussions of how to achieve energy savings, perhaps some movement to the tropical highlands is in order. And, if further impetus is needed, consider that this is also where most of the world's coffee is grown. Current American political dissatisfaction with the 2015 Paris climate accord hinges on its perceived economic risks to the industries that powered the country's 20th-century explosion in productivity and living standards for much of the population. While futurists promise everyone will be better off when the transition to cleaner and more-efficient energy is complete, many still fear those promises are hollow -- leading to a society dominated by overlords of the finance-technology-energy complex -- and are based on a false premise of imminent global catastrophe. Harborers of these reservations naturally advocate for applying the brakes to investments in measuring, preparing for, and adapting to climate changes of any stripe, and consider such efforts a gigantic boondoggle. Independent of climate projections, geopolitics, and the subtleties of national moods, I thought it worthwhile to take a moment to assess the indisputable evidence at hand for the observed connection between temperature and various economic measures. In other words, to point out there while there is a real cost to doing something about a warming world, there is also a cost to doing nothing. The most-salient point is that there exists abundant evidence that high temperatures, like poverty, exact a kind of "cognitive tax" that seems to be an evolutionary adaptation to scarcity of a resource critical for survival. This temperature-productivity relationship has long been observed anecdotally, starting with Montesquieu in the 18th century (an "excess of heat" makes people "slothful and dispirited"). Quantitative studies have estimated that combating this heat with air conditioning results in increases in productivity from 5% (sedentary call-center work) to 25% (active kitchen work), and that the amount of outdoor labor -- from construction to gardening -- able to be performed during the hottest months could fall by half by the year 2200. Even in current conditions, outdoor laborers in Nicaragua opt to work about 20 fewer minutes per day (about 4%) when daily-maximum wet-bulb temperatures exceed the threshold of 26 C, according to public-policy graduate student Tim Foreman whom I spoke with at a recent conference. A listing of the results of some previous studies are shown in the figure below. Physiologically, these relationships are logical, given the body's reluctance to risk overheating itself and the decreasing effectiveness of our main cooling mechanism (sweat) at higher and higher temperatures. On an international scale, for poorer (primary-resource-dependent) countries, every 1 C temperature increase is associated with a decrease in economic growth of 1.3 percentage points. A different study found productivity peaks at an annual-average temperature of 13 C, irrespective of a country's wealth, though it is only at daily maximum temperatures above 30 C that the relationship becomes meaningful. Thus warming is expected to help contribute to raising economic growth in cool countries, while subtracting from growth in warm ones. This is even the case within the United States, but as with the country comparisons, the definitive reason for this relationship's persistence despite electricity, air conditioning, and the increasing prevalence of indoor work is still at large. Less expected, perhaps, is the link between temperature and mood, which is a nontrivial consideration on a personal level (e.g. in deciding where to accept a job or attend a school), but is rarely mentioned as it relates to society-wide impacts (e.g. with respect to possible changes in temperature or storminess in a particular region). I argue that this cost/benefit of climate change should be included in estimations of the overall effects. Leaving aside for a moment all other changes, the historical distribution of weather conditions sets a baseline for the culture of a region, month by month throughout the annual cycle, and this expectation may be considerably disrupted if monsoons, beach weather, snowstorms, etc. arrive at different times or not at all. It may be that this mood-weather relationship helps explain the observation that countries enduring clusters of repeated meteorological shocks are less able to recover on a unit basis than those for which the shocks are more evenly spaced out. And it's also likely a contributing factor to the expected erosion of economic gains in already-hot countries, which will face not only more-extreme heat but also more-severe storms. All in all, it's abundantly clear that we not only shape the climate to some extent, but that the climate also shapes us -- our productivity, our mood -- in subtle yet unrelenting ways. It's even the case that temperature affects things as intimate, individual, and seemingly intrinsic as condom usage (and resultant HIV transmission rates). And this is not to mention the myriad other effects on our health. All of which goes to show that, especially going forward, the very term 'natural disaster' must be re-evaluated as regards anthropogenically-influenced changes in temperature, pollutants, and storms. While there may be reasonable debate about the location and magnitude of these changes, and the cost of the interventions intended to address them, there should be no doubt that they affect us all, no matter who we are or what we do. This rather complex table summarizes the results of many earlier studies investigating the effects of temperature and pollutants on the quality of work performed in sedentary indoor settings, with strong negative effects reported especially for volatile organic compounds [VOCs] and high temperatures. Source: Mendell and Heath, 2005. In billions of years,
Us. And this is what we do? The world keeps turning. |
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