Kevin Kelly on cities and nature

In his thoughtful and interesting blog "The Technium" Kevin Kelly addressed the question why people migrate to cities [see http://www.kk.org/thetechnium/index.php].

Kelly ponders, cities

"…seem like machines eating the wilderness, and many wonder if they are eating us as well. Is the recent large-scale relocation to cities a choice or a necessity? Are people pulled by the lure of opportunities, or are they pushed against their will by desperation? Why would anyone willingly choose to leave the balm of a village and squat in a smelly, leaky hut in a city slum unless they were forced to?"

One of the repercussions of the search for urban opportunities and rural quality of life is the formation of rural-like suburbs and the outward spread of cities. We wrote in the past about the leap-frogging spatial dynamics that results [Benguigui, L., Czamanski D. and Marinov, M., “City Growth as a Leap-Frogging Process: an Application to the Tel Aviv Metropolis” in Urban Studies, 38(10), 2001, pp. 1819 – 1839].

I am concerned that stylized facts and observation of cities at an inappropriate resolution leads to wrong conclusions concerning the impact of cities on nature. In fact we do not know enough about this interaction. In a recent paper we reviewed the little that is known [Czamanski, D., Benenson, I., Malkinson, d., Marinov, M., Roth, R., Wittenberg, L., "Urban Dynamics and Ecosystems" in International Review of Environmental and Resource Economics, 2, 2008, pp. 1-45]. A tentative conclusion from our review is that sprawl is a contributor to biodiversity and not destroyer of nature. Our research group is engaged in a multi-year empirical study of this phenomenon.

young and old cities

Before long I will be teaching again my urban economics course. I started to re-read my lecture notes and the new papers that were published in the last 12 months.

I am deeply disappointed with the way my fellow professional urbanists view cities and the prescriptions that they conjure up to cure urban ills that may or may not exist. My disappointment stems from the clear dissonance between what continues to be published in the professional literature and evidence. Thus for example, cities are said to expand outwards like sea waves in all directions. They are not supposed to leave any un-built areas in their wake. Open spaces within and around urban areas are thought to be a relic of early urban evolution. The truth is quite different.

Like the proverbial seven blind men, we see cities partly and imprecisely. I would like to persuade my students to see cities from a non-traditional perspective. It is my intention to provide them with a distant, and yet close, perspective and to change the way they think about their home.

There are two fundamental problems with the way that professionals have been looking at cities. Their vision is obscured by the use of statistical data. The information they use is granular and their chunky data display only that which statistical units reveal. Census bureaus and other government producers of statistics view cities through a prism that "divided" cities into statistical areas and gather data accordingly. Statistical areas are relatively large. Within such relatively large area there are many buildings, activities and people. They display a great diversity of things. In official statistics, each statistical area provides a distorted, average, image of the activities within it and the city as a whole is seen as an average of these averages. The vast diversity that characterizes real cities at the very local neighborhood level is simply lost. Therefore, the stylized facts about cities do not reflect their reality.

The representation of a phenomenon by its average occurrence can be innocuous only under very special circumstances. The average can represent the population in cases that the number of extreme occurrences is very small relative to the average-size cases and that the number of extremely large and extremely small events is similar. Such populations are termed "normal", or Gaussian.

The world of cities is not Gaussian. It is characterized by fat tails. For example, in very few countries is the population of cities very large. The vast majority of cities have small populations. Very many other urban characteristics display the same fat tail distribution. Indeed, it is almost an universal characteristic of cities.

In the least, large and small cities do not represent the same phenomenon. It is as if we were to understand human physical activities by means of a typical individual. Abilities, performance and repercussions for kids, young people, middle-aged individuals and for old people would be seen as equivalent. Obviously, the stylized facts and reality would be disparate. So it is with cities. There young cities and old cities, etc. Cities possess characteristic times and we need to understand them in a dynamic context and not through still, Polaroid-like, photographs.

There are very many other implications of fat tail distribution of city sizes. Perhaps the greatest distortion that results from the use of such data is our understanding of sprawl and its repercussions. But, on this I will write later.

Earth's warming and evidence from Mars

I just read (via Peter Gordon [http://www-rcf.usc.edu/~pgordon/blog/]) that yesterday's LA Times reported global warming on Mars. As Peter writes this is uncomfortable evidence for those that deny that humans contribute but a fraction to changes in temperatures on earth.

Clue to Mars' warming is seen

The planet's darkening surface could account for its temperature rise, scientists report.

Global warming on Mars? It turns out you don't need belching smokestacks and city-choking traffic to heat up a planet. Changes in surface reflectivity may also do the trick, according to research published Thursday in the journal Nature.The research team, composed of scientists from NASA's Ames Research Center in Northern California and the U.S. Geological Survey, compared images of Mars taken by the Viking missions in the 1970s to pictures taken a quarter century later by Mars Global Surveyor.The surface was noticeably darker in the new pictures, said Lori Fenton, a planetary geologist at the Carl Sagan Center in Mountain View, Calif., who worked with Ames scientists on the project. Plugging in a climate model developed at Ames, the research team said the changes in surface reflectivity could account for a 1 degree Fahrenheit rise in the surface temperature of the planet. "That's a significant amount," said Rich Zurek, lead Mars scientist at the Jet Propulsion Laboratoryin La Cañada Flintridge, who was not involved in the research. The scientists believe the changes in surface reflectivity —known as albedo — are caused by wind-driven dust storms that occasionally sweep the entire Martian surface. The storms fill the air and cover the surface with fine grains that are more reflective than the bedrock. Several big storms preceded the visit of Vikings 1 and 2 in 1975, Fenton said. Comparatively, there was less heavy wind and, consequently, more light-absorbing bedrock in the picture taken by Mars Global Surveyor in 2000. If Mars is getting hotter, that could explain one finding that has puzzled planetary scientists since it was discovered several years ago: the loss of carbon dioxide ice at Mars' south pole. The CO2 ice forms a cap on top of water ice that ranges from several feet to several hundred feet in thickness. Each of the last few years, scientists have seen holes develop in the CO2 layer late in the Martian summer. So does all this mean Mars is undergoing a new round of climate change like the one that dried up its ancient lakes and drove its waterunderground? Fenton is unsure. What's going on at the south pole "is an indication of at least regional temperature change," she said.

So what's between good science and the earth warming hypothesis?

Eclectecon just posted
[http://www.eclectecon.com/] the following:

Chris Essex, Ross McKitrick, and Bjarne Andresen recently published a paper [Jl. of Non-Equilibrium Thermodynamics, Vol 32, 1 - 27, 2007] in which they demonstrate that using different metrics leads to different conclusions about whether the earth is really warming. Here is the abstract:
Physical, mathematical, and observational grounds are employed to show that there is no physically meaningful global temperature for the Earth in the context of the issue of global warming. While it is always possible to construct statistics for any given set of local temperature data, an infinite range of such statistics is mathematically permissible if physical principles provide no explicit basis for choosing among them. Distinct and equally valid statistical rules can and do show opposite trends when applied to the results of computations from physical models and real data in the atmosphere. A given temperature field can be interpreted as both ‘‘warming’’ and ‘‘cooling’’ simultaneously, making the concept of warming in the context of the issue of global warming physically ill-posed.
Their conclusion is strong [emphasis added]:
There is no global temperature. The reasons lie in the properties of the equation of state governing local thermodynamic equilibrium, and the implications cannot be avoided by substituting statistics for physics.... Since temperature is an intensive variable, the total temperature is meaningless in terms of the system being measured, and hence any one simple average has no necessary meaning. Neither does temperature have a constant proportional relationship with energy or other extensive thermodynamic properties.Averages of the Earth’s temperature field are thus devoid of a physical context that would indicate how they are to be interpreted, or what meaning can be attached to changes in their levels, up or down. Statistics cannot stand in as a replacement for the missing physics because data alone are context-free.Assuming a context only leads to paradoxes such as simultaneous warmingand cooling in the same system based on arbitrary choice in some free parameter. Considering even a restrictive class of admissible coordinate transformations yields families of averaging rules that likewise generate opposite trends in the same data, and by implication indicating contradictory rankings of years in terms of warmth.The physics provides no guidance as to which interpretation of the data iswarranted. Since arbitrary indexes are being used to measure a physicallynon-existent quantity, it is not surprising that different formulae yield different results with no apparent way to select among them. The purpose of this paper was to explain the fundamental meaninglessness of so-called global temperature data. The problem can be (and has been) happily ignored in the name of the empirical study of climate. But nature is not obliged to respect our statistical conventions and conceptual shortcuts. Debates over the levels and trends in so-called global temperatures will continue interminably, as will disputes over the significance of these things for the human experience of climate, until some physical basis is established for the meaningful measurement of climate variables, if indeed that is even possible.It may happen that one particular average will one day prove to stand outwith some special physical significance. However, that is not so today. Theburden rests with those who calculate these statistics to prove their logic and value in terms of the governing dynamical equations, let alone the wider, less technical, contexts in which they are commonly encountered.

Cultural facilities tend to cluster (in Tel Aviv)

In New York City there is the theater district. In London there is the west end. In Tel Aviv the cultural facilities seem to be randomly distributed. But, are they?

Gilles Benguigui, Idan Porath and I spent some time examining the variety of such facilities in Tel Aviv. First we used the old nearest neighbor method to identify clustering.

The method calculates the ratio between the average short distance between every two points and the expected average short distance of completely spatially random distribution. The ratio of the two is an index for the spatial point distribution and for spatial order.

The method is subject to some well-known drawbacks. It indicates a random distribution of points in cases that there are some clusters with random distribution of points inside the clusters. Also, the results are sensitive to the choice of boundary of the area within which the points are distributed. When the boundary of a geographic entity is ill-defined defined, it is difficult to apply the method.

To deal with this problem we created the all distances analysis. It is free of these defects. The all distances analysis method takes into account the distances between every point to all other points in the examined area.

We concluded that despite first appearances the cultural facilities cluster. Furthermore, there are several distinct clusters, each possessing particular characteristics. These characteristics were confirmed by a detailed survey of users.

Semester break at the Technion

It is the end of the Fall/Winter semester at the Technion. We start late (in October) and finish in February. The Spring semester will start in mid-March and end in the beginning of July.

The upshot is that I am off to a conference and visits to various campuses in the USA.

Jerusalem will be environmentally friendly, but ultra-orthodox

Jerusalem is a relatively poor city. It is the home of a large ultra-orthodox population that is characterized by men who study Torah and women that produce very many children and work to support their families. It is also the home of government employees. Although there is a high-tech industry in Jerusalem, many of its employees reside outside city limits.

For many years now, policy makers in Jerusalem have targeted ways to attract new, young and professional population to the city. One of the means that has been proposed is to create a new stock of housing for these families, away from the religious neighborhoods. It was hoped that by so doing the stigma of Jerusalem as a place dominated by "blue laws" will be replaced by an image of comfortable suburban living in the midst of nature in the Judean hills.

A land- use plan was commissioned from the Israeli/Canadian architect Moshe Safdie. The plan proposed 20,000 housing units west of the city around the main road connecting Jerusalem with the center of the country.

Today, the Israel National Planning Board rejected the plan after a prolonged debate to the sound of vocal protest from various groups wishing to preserve the green areas around the city. The mayor of Jerusalem has adopted the view that it is possible to create a sufficient stock of housing within the current city limits. Based on a new study he claims that it is possible to build 40,000 housing units within the city.

There is no doubt that dense urban fabric is to be preferred. It creates a smaller environmental footprint by encouraging the use of public transportation facilities and lowers CO2 emissions. However, there may be a significant cost associated with the new policy. It is my suspicion that Jerusalem will find it difficult to attract young, upwardly mobile families and that the outflow of young people to Tel Aviv will continue. It is likely that we will have a green , non-pluralistic and relatively poor capital city.