GaWC Research Bulletin 447

(A)

A Trans-modern Understanding of Anthropogenic Climate Change through Cities

P.J. Taylor^*, G. O'Brien^* and P. O'Keefe^*

Abstract

It is argued that the process of cities in networks is integral to anthropogenic climate change and that both can be traced back many millennia, far before conventional views of their respective beginnings. This emphasizes a different relation between cities and climate change that has relevance for both climate science and policymaking. Jacobs' theory of urban economic development is selected as the most suitable city process because its integration of internal and external relations of cities generating localization. This provides a demand theory of economic development. Anthropogenic climate change is depicted by Ruddiman's thesis of long slow change resulting from land cover removal for farming over many millennia. Jacobs and Ruddiman's ideas are linked through Jacobs' positing demand for food in embryonic cities as the stimulus for the invention of agriculture and consequent land cover removal. Using this link, a geohistorical narrative is created to serve as a broad frame for the argument that priority be given to demand (contemporary consumerism) in understanding and responding to climate change.

Keywords

anthropogenic climate change; cities; city networks; climate policy

 

‘There is little question about the pressing realities of climate change. But does the urgency to communicate the realities of climate change override the need for an adequate historical interpretation of the problem? Conceptualizations of a problem and efforts to resolve that problem are always tightly connected. So too are the ways we think the origins of a problem and how we think through possible solutions' Moore (2015, 4)

“… determining when radical physical changes in the Earth system happened provides a basis for determining which human activities were responsible, and thus what measures humans might take to prevent the change from reaching catastrophic proportions” Angus (2015, np)

Introduction

In her recent discussion on situating anthropogenic climate change, Ann Ruddick (2015, 3) has identified the idea of the urban being both cause and cure as ‘a truism'. Calling something a truism evokes two quite different responses. On the one hand it suggests that a statement has become a clich é, a platitude that requires little further thought. On the other hand it states an axiom, a statement upon which to build an argument therefore necessarily requiring careful scrutiny. We proceed on the basis of the latter. In particular bringing cities to centre stage is used to interrogate the temporality and spatiality of anthropogenic climate change.

For most scholars the temporality of anthropogenic climate change is settled: starting with the ‘industrial revolution', it is the massive growth in production based upon carbon energy sources that has altered global climate. However Moore (2014, 2) refers to this as an ‘easy story', one that does not understand the basic social mechanism that ultimately created the industrialization. Dismissing what he terms the Two Century Model, he traces today's ecological crisis back to the ‘long sixteenth century' as a consequence of the modern world-system creating a capitalist world-ecology. But there is a very different critique of the focus on industrialization from Ruddiman (2003) based on direct study of atmospheric changes: he argues that anthropogenic climate change began 8,000 years ago. To be sure there is rapid change in the last two hundred years but this follows a very slow change over many millennia that has been ignored. 200, 500 or 8,000 years, clearly the temporality of anthropogenic climate change has been problematized. We will show that bringing cities into the argument clarifies this confusion of temporalities.

The spatiality of anthropogenic climate change is intimately related to the temporality: the conventional industrial position indicts the ‘West' and latterly the ‘Global North'. Moore features a broader geography of exploitation on a wider systemic basis relating to the incorporation of the Americas; Ruddiman introduces a completely different geography relating to inventions of agriculture resulting in large-scale land clearances. None of the above particularly focus on cities but there is a clear synergy between the environmental and social processes in the Two Century Model with urbanization commonly viewed as a concomitant ‘twin' of industrialization, which has culminated in the globalizations of human activities. Thus in urban studies cities have been treated as global in scale for more than two decades (Friedmann 1986; Sassen 1991); more recently this has been expressed as ‘planetary urbanization' (Brenner 2014). The latter uses ‘planetary' to express a worldwide spatial fabric consequent upon economic globalization, not unlike Mackinder's (1904) announcement of ‘global closure' in political globalization a little more than a century ago: both are premised on multi-scale projects eliminating an erstwhile outside. But we will argue that this new urban spatiality should not be interpreted as supporting the conventional temporality position. There may have been globalization of human activities but this does not translate into climate process; it makes no sense to argue for a recent ‘globalization of climate', climate comes as ready-made global. Thus in all three posited temporalities the climatic consequences of the human activities are global in scale; they each postulate planetary effects. We will show that bringing cities into the argument clarifies this potential confusion of spatialities.

We use Jane Jacobs' (1969, 1984, 2000) theory of cities as economic development to integrate the urban with the temporality and spatiality of anthropogenic climate change. Her seminal work is specifically appropriate in this context for three key reasons. First, the theory is articulated on inside/outside relations as export and import replacement modes of economic growth through cities. This process of cities as the engine of economic development internalizes outside spaces, a continuous transformation that sets the temporality of our subject. Second, this process directly informs scalar inter-relations. The dominant import replacement activity in this theory is a continuous generation of homegrown production, a localization creating concentrated, complex city economies within wider urban fabrics. Third, this conception of city process is set in a supply and demand framework wherein the latter that is the root cause of change. This is very important for understanding anthropogenic climate change because policy prescriptions generally engage with supply, most notably in international carbon reduction negotiations. Prioritizing cities à la Jacobs switches concern emphatically to demand: rapacious urban demand.

Jacob's urban theory is an argument that is historically situated across the last 8,000 years. That is to say, it shares a temporality with Ruddiman's long view of anthropogenic climate change (Taylor et al 2015). In this paper we explore this link in detail. Both the 200-year and 500-year positions on anthropogenic climate change are premised on modernity as the basic social structure generating the change; the different timings result from two different conceptions of modernity, industrial and world-systems, and thus the timings of its beginnings. Ruddiman's combination of a long slow anthropogenic climate change with a recent short fast change transcends any historical notion of modernity. In addition, we agree with the widely accepted view that adaption to the climate change will involve creation of a new social structure that transcends modernity's insatiable use of the environment. This is what we mean by our trans-modern approach to anthropogenic climate change. We do not use history as provider of lessons, although it can indicate possibilities, rather we trace a pathway of change before, through, and beyond modernity. Such an integrative position on future and past relates to our opening quotations as guides to our argument: we follow Moore in his linking conceptualization to origins as necessary for credible solutions, and with Angus, we consider understanding the timing in linking physical changes to social changes as a necessity for moving towards policy that might work. Thus we produce a new broad canvas from which to engage with contemporary policymaking responses to climate change.

Our reasoning proceeds in four steps. First we elaborate on Jacobs' theoretical understanding of cities, which is the social process in our argument. Second, Jacobs' ideas are used to make a contribution to Ruddiman's early anthropogenic climate change to illustrate cities' potency. Jacobs' ‘city first' position (in relation to the origins of agriculture) adds an extra, we would say necessary, dimension to Ruddiman's early human impact. Third, combining Jacobs and Ruddiman we create a new geohistorical narrative placing cities at the heart of anthropogenic climate change. Covering many millennia, this is the story of a uniquely dangerous species whose material reproduction is becoming enormous, simply too big for the Earth. Fourth, this narrative is employed to investigate the ‘how' (political and policy practicalities) and the ‘what' (guide, destination, vision) of current responses to anthropogenic climate change. Our multi-millennia thinking locates policies for confronting demand (i.e. mass consumption) centre stage where currently policies that tackle supply (e.g. carbon limits) are to be found. We identify this as a structural complacency and argue for ‘post-normal' thinking to make sense of current policymaking limitations.

Understanding the power of cities

Jacobs' (1969, 2000) theory of urban economic development builds upon her classic book on American cities (Jacobs 1961, 442-62) in which she famously concluded that ‘organized complexity' was ‘the kind of problem a city is'. This promoted bottom up agency over City Hall. There are hints of this idea in some city and climate change writings, for instance, Bulkeley (2013, 11), referring to Foresight (2008), identifies the ‘self-organization of independent actors' as ‘radical possibilities for living different urban lives in reconfigured urban economies'. More generally, Easterly (2013) has argued strongly for all economic development to be based upon unplanned bottom up processes. What we do in this section is to tie down this thinking specifically to the nature of cities as loci of economic development. The theory in presented in two parts; first, identifying the special nature cities and city life, and second, delineating the mechanisms that result from this specialness.

The Fundamental Advantages of Cities

Cities emerged at various times and places across the world as special settlements orchestrating local/non-local relations. According to Jacobs (1969, 35):

‘… in modern and historical times, no creative local economy – which is to say, no city economy – seems to have grown in isolation from other cities. A city does not grow by trading only with a rural hinterland. A city seems always to have implied a group of cities, in trade with one another. '

Living in a city as part of a network of cities means a whole new world of enhanced communication, in terms of both quantity and quality. For most of its existence, humanity lived in hunter-gatherer bands of about 150 people involving just intra-band communication plus local contact with neighbouring bands. In contrast, the invention of cities and their networks enabled daily contact with far larger numbers of people, both within and between cities. In addition to this quantitative boost, there was a qualitative effect: regular network relations between cities produces contact with a diversity of non-local people, some of whom move to live in new cities, creating the beginnings of urban cosmopolitanism. It has been estimated that in Catalhoyuk about 7000BC (in Anatolia, one of the earliest known cities) residents had a human communication enhancement greater than pre-urban people by a factor of nearly 2,700, and for Uruk (in Mesopotamia, perhaps the first great city) about 4000 years later the enhancement factor was over 550,000 (Taylor 2013, 99). In other words living in cities totally transformed the density and diversity of communications of people providing direct access to so much more information and knowledge than could ever be experienced in previous non-urban worlds of small human bands.

What difference does this make? According to Glaeser (2011, 7) all this additional communication enables city residents to become ‘smarter' than their less connected country cousins; not because they are personally more intelligent but because of enhanced opportunities: they have more and diverse people to learn from who are also ‘smarter' from being in cities. In particular, he argues that ‘cities speed innovation by connecting their smart inhabitants to each other' to become very creative places. This is the reason cities have such a strong historical track record for creative change: ‘cities' are literally synonymous with ‘civilizations', which are classically defined as societies organized through cities. But being ‘smarter' is not just about economic innovations; living in cities can instigate collective changes in ways of living. For instance, in the twentieth century, environmental concerns for the future focused upon global population growth featuring predictions between 12 and 15 billion people. But Ehrlich‘s (1971) famous ‘population bomb' has somewhat fizzled out with peak population now expected at 9 to 10 billion. This massive reduction of up to a third is due to the changed reproductive decisions of women living in cities. As Brand (2010, 55) tells it: ‘City dwellers have few children – the billion squatters like everyone else. Thanks to a by-product of urban growth, the core environmentalist panic about over population is quietly being undermined'.

This example of mass behavioural change – what Pearce (2010, 246) calls ‘the feminization of cities' - shows the potential global power of cities in our century.

Glaeser (2011) has titled his book The Triumph of the City reflecting the oft-quoted fact that urban dwellers are now a majority of the world's population; he asserts that we are now ‘an urban species' (p. 1). But passing the 50% threshold is just part of an incessant trend, a global urban change that is expected to result is perhaps three quarters of the world's population being urban around mid-century. From the perspective of the communication argument this change has potentially immense consequences: the twenty first century's billions of people are singularly special because, as largely urban dwellers, they encompass city potential for changing ways of living at an historically unprecedented rate: the global urban capacity to ‘cure' in Ruddick's ‘truism' with which we started. But before we explore the real significance of this it is necessary to specify more precisely the actual mechanisms that make cities so potent.

Jacobs' Mechanism of Development

When translated into urban economics the two sources of communication advantage – dense and diverse links – are treated as externalities. An externality denotes the context within which a firm operates that is not market defined (i.e. it is ‘external' to the market). Cities provide two important positive externalities for firms: (i) agglomeration/cluster externalities within cities whereby firms can take advantage of being close to other firms, and (ii) network/connectivity externalities between cities whereby firms can take advantage of connections with other cities. In combination these make cities into rich places of information flows. As knowledge hubs largely based upon face-to-face contacts in a learning milieu, cities are where both concentrated and cosmopolitan economic environments are to be found.

According to Jacobs (1969), economic development is a special case of economic change. It is generated by two master economic processes, innovation and import replacement, which are both features of city creativity. In this argument innovation is a function of the size and complexity of cities, where urban problems generate new demands that only these creative places can satisfy through new production and consumption. Import replacing derives from the diffusion of innovations through city networks of creative places, where innovations can be improvised for local production and consumption. Both processes generate new work thereby increasing the complexity of a city's division of labour. It is this that specifically defines economic development. An economy can grow by just increasing what is already being produced – adding more old work to existing old work such as doubling the output of a factory – but this change does not diversify a city's division of labour and hence does not qualify as development. Thus cities are exceptional settlements because of their complex dynamic divisions of labour resulting from their innovations and import replacements: it is these processes that make cities the prime units of economic development.

One of the key advantages of this urban economic theory is that it provides a means for understanding the internal and external relations of cities together. In the broader literature, these are usually treated as agglomeration/cluster processes (Fujita and Thisse 2002) and network/connectivity processes (Taylor 2004) separately. In Jacobs' work they are entwined in multiple urban episodes of economic development in which the crucial mechanism is import replacing. This generates explosive economic growth, short periods of time in which a city rapidly develops into a larger and increasingly complex economy. In contrast, the growth generated by exporting produces only relatively slow economic growth. In fact, the more a settlement's economy is dominated by exporting, the more it becomes dependent on distant markets and will experience little or no development even if exports (old work) grow. The limiting cases are ‘company towns' producing one product that is wholly exported and thereby constitutes a simple dependent economy with little or no development capacity. However, in complex cities exporting remains important for two reasons. First, exports are obviously necessary for the process of import replacing (from innovation in other cities) to operate. Second, a set of cities vibrantly import replacing (using and adapting each other's innovations) will eventually become more and more economically similar, increasingly negating the need for trade and thereby stagnating – maintaining exports is required to prevent this eventuality. Thus in successful cities exporting and import replacing operate together: a continual stream of innovations is needed to initially spark network vibrancy through export and diffusion of innovation, and then import replacing through improvisation of other's innovations, followed by innovation diffusion to keep the network vibrant and dynamic. This economic development spiral is a combination of exporting and import replacing, creating more and more complex divisions of labour within cities and through their networks.

This theory posits a world divided between two types of settlement with contrasting economies: complex economies of cities mutually linked through networks, and simple economies of small towns, villages, and farms dependent on cities. Jacobs (1984) describes in detail how this division enables cities to project their economic power and mold far-off economic landscapes to their own needs. The crucial point is that this is a demand theory of economic change wherein demands generated in cities transform economic activities and fortunes in both urban and rural realms. Put simply, what we argue is that cities are inherently demanding and anthropogenic climate change is an unintended consequence.

Linking to Ruddiman’s early anthropogenic climate change thesis

Ruddiman's (2010) basic method is to show how the Earth's climate varies over the long term – what he calls “nature in control' – and then to home in on change anomalies in the recent past, which he argues can only be explained by human activities. In this section first we present a summary of Ruddiman's thesis, and second we bring cities into the argument.

Ruddiman's Time Lines for Early Anthropogenic Climate Change

The thesis for change from ‘nature in control' to ‘humans in control' can be set out as follows.

1. Nature in control is described for both high latitude ice ages and tropical monsoons in relation to Earth's orbital changes. These two cases are related to atmospheric concentrations of the two greenhouse gases, carbon dioxide and methane respectively
2. Glacial cycles were superimposed on a longer-term cooling trend about 2.75 million years ago and are determined by changes in the Earth's orbit that affect the amount of solar radiation received. Cycles of 41,000, 22,000 and 100,000 years are identified in a sequence of between 40 and 50 ‘ice ages'.
3. Alignment of radiation maxima from orbital tilt (41,000 years) and precession (22,000 years) produces radiation peaks approximately every 100,000 years removing ice sheets from the northern hemisphere. The most recent occurred from 16,000 years ago leading to minimum ice cover 6,000 years ago.
4. In terms of CO 2 concentrations in the atmosphere, Ruddiman finds peak values in relation to the 100,000 year cycles: for the three cycles before the most recent, the peaks occur just before the minimum ice cover
5. In the current cycle the natural CO 2 peak is found 11,000 years ago before minimum ice as previously but the subsequent decline of CO 2 does not continue as expected: about 8,000 years ago the CO 2 trend reverses direction showing increasing concentration of CO 2. It is this anomaly that Ruddiman interprets as humans beginning the take control of climate change.
6. The strength of monsoons is driven by changes in solar radiation caused by the 22,000 year orbital cycle producing a wet-dry climatic sequence
7. A summertime maximum for solar radiation in the northern tropics occurred 11,000 years ago since when radiation levels have declined to a minimum, so that we are half way through a 22,000 year cycle today.
8. In terms of CH 4 concentrations, generally these are at a maximum at the peak of solar radiation – the wet period produces more vegetation – and the CH 4 levels subsequently decline as the solar radiation reduces and a dryer climate prevails.
9. In the current cycle the CH 4 levels do decline from 11,000 years ago but this abruptly stop and reverse 5,000 years ago. From this point the concentration of CH 4 in the atmosphere increases. This second anomaly is interpreted by Ruddiman as a further effect of humans beginning the take control of climate change

In creating his early anthropogenic argument Ruddiman specifies separate processes to account for the two green house gas anomalies at 8,000 and 5,000 years ago, both consequences of agricultural activities. Increasing CO 2 from about 8,000 years ago results from the transformation of land cover due to large-scale deforestation for farming. Increases CH 4 from about 5,000 years ago results from the development of wetland rice production in tropical Asia through a dryer period that maintained and increased rotting vegetation levels. In both cases he argues that anthropogenic induced land cover change modified terrestrial ecosystems to such a degree as to change global climate. Thus Ruddiman's (2010, 6) seminal contribution to climate change science is to add a relatively slow and long rise in greenhouse gases to the conventional identification of rapid rise in green house gases over the last two hundred years. However, evoking the first stages of agricultural development as the human activity generating early terrestrial atmospheric alterations has received particular skepticism within climate science. And this is where Jacobs (1969) re-enters our argument: she links cities to agricultural revolutions in her ‘cities first thesis'. And making this link creates a contribution to Ruddiman's defence of his early anthropogenic climate change thesis by providing a much more powerful social mechanism of change.

Bringing Cities in

A very obvious response to the early anthropogenic climate change thesis is that there were simply too few people living in these early times to have made such an impact. Ruddiman has countered this criticism in three main ways. First, the time effect: the impact of changing land cover has been compounded over a very long period. Second, the numbers of people involved in the rise of agriculture has been under-estimated – Gignoux et al (2011) show populations growths in double digits across different regions when agriculture appeared. Third, Boserup's (1965) thesis on the relationship between agricultural intensification and population growth is used to indicate that because earliest agriculture had least population pressure it produced initial very high per capita land cover changes (Ruddiman and Ellis 2009; Kaplan et al 2010). These arguments are brought together in Ruddiman's (2013) state-of-the-art summary of his thesis and we have no disagreement with them. Rather, by bringing in Jacobs' cities first thesis we add a fourth counter to the idea that early peoples could not have affected global climate change. Not only were there more people than generally thought, they were also beginning to be settled in a new geography – cities. But bringing in cities is not just an addition to Ruddiman's thesis; it provides an explanation for why and how agricultural begins, and it produces a common mechanism of social change capable of creating climate change for both of Ruddiman's impact eras.

The key connection between Jacobs' and Ruddiman's ideas is that for Jacobs, agriculture is a very significant import replacement for the earliest cities. Embryonic cities derive from Neolithic trade networks when production (new work) is added to trading camps. With the consequent urban population growth, existing food procurement from hunter-gathering practices is unable to satisfy the increased demand: agriculture is invented to meet the shortfall. This is Jacobs' ‘cities first thesis': cities emerge in the human story before farming. The conventional view of the very first cities appearing in Mesopotamia several millennia after the coming of agriculture is based on a supply theory of urban origins – cities only appear when agriculture has advanced enough to generate food surpluses to support urban life. To counter this traditional view the alternative demand theory simply asks why hunter-gatherers, whom Sahlins (2004) terms the ‘first affluent society' with few wants but much leisure, should choose to invent agriculture and the concomitant extra work (Taylor 2012a; 2013 102-13)). Jacobs' answer is that there was no such rustic invention; agriculture is an early expression of the power of cities to mold their environs for their specific needs. Evidence for early cities across the world is briefly reviewed in Taylor (2013, 138-44). From an orthodox archaeological perspective these large settlements in ‘wrong places at wrong times' cannot be locales for inventing agriculture because they are not recognized as cities; this issue has recently been debated, see Smith et al (2014) and Taylor (2015). However Jacobs' shift in interpretation of farming origins in no way lessens the importance of agriculture in terms of the changing land cover outcome as argued by Ruddiman, rather it interprets agriculture as an intermediate step in a process that has its origins in urban demand.

Jacobs-Ruddiman anthropogenic climate change narrative

Humans are different from other species in having two means of social reproduction. All species harness the immediate resources of their environment thus creating a local dependence. The local can be a fixed territory or a moving supply area (seasonal path). Uniquely humans also draw on non-local resources, movement of goods to them from afar (Jacobs 1992). This has always been very clear from archaeological studies, where non-local artifacts – stone tools from distant specific geological sources – are present in excavations. Archaeologists call this ‘the release from proximity' (Rodseth et al 1991, 240); although Gamble (2007, 211) has noted that material from further than ‘daily foraging range' usually constitutes less than 1% of an excavation assemblage, it does represent ‘the local rule broken' and that is the key point. It is not the quantity that matters; a qualitative difference in the manner of social reproduction has been broached. However, the problems of developing the necessary trust with strangers to enable routine trading kept the non-local contribution to social reproduction quantitatively unimportant (Curtin 1984; Graeber 2011). Overcoming this problem enabled the rise of cities.

Evidence of the earliest agriculture is about 12,000 years ago but Ruddiman (2010) shows its climatic impact only from 8,000 years ago. This time lag represents a response time of a slow transition, the first stirrings of urbanization, a stuttering into being of city networks with their new demands for food (Soja 2010). These initial networks are relatively fragile; overall growth is slow but by 8,000 years ago there is clear evidence of substantial urban settlements trading through complex divisions of labour as evidenced by Jericho and Catalhörük (Jacobs 1969; Soja 2000, 2010,; Taylor 2012a, 2013). This is the breakthrough of the non-local becoming significant in macro social change. It is this development of multiple vibrant city networks whose creation of new landscapes of agriculture instigates the turnabout of CO 2 that Ruddiman (2010) reports.

However, initially, the long-term resilience of early cities was problematic: surrounding agricultural supply becomes more distant as soils are exhausted finally creating empty quarters and lost cities (Pauketat 2004; Taylor 2013). This outcome is overcome 5,000 years ago with the Mesopotamian city network based upon sustainable irrigation agriculture. Ruddiman (2010) emphasizes tropical Asia's rice cultivation at this point, which he links to rapid population growth; here this is interpreted as early Chinese city networks creating large new demands for food. South Asian and Egyptian riverine cities can also be pushed back to 5,000 years ago. Collectively this is the beginning of the era of large cities in large networks of cities The first city of 40,000 people is identified in 3300BC as Uruk in Mesopotamia; by 2800 the city has a population of 80,000 and with 10 other cities in its network, the urban population of the region is over a quarter of a million (Modelski 2003, 22; Taylor 2013, 114). This new level of urban demand requires a social reproduction logistics at a whole new scale, not to mention the outputs, both waste and exports. It is the rise of large cities and their consumption and disposal needs that instigates the turnabout of CH 4 that Ruddiman (2010) reports.

Importantly, such new scales of social activity require new means of governance: the world-changing invention of states (Smith 2003; Yoffee 2005), first as city-states and then empire-states incorporating multiple cities (Taylor 2012a, 2013). This new political dimension is vital to understanding the relatively slow rise of large cities before the modern era. What is happening is that in traditional empires the city development process is replaced by plunder and tribute as the main means of wealth accumulation (Taylor 2013). The largest cities are now typically the imperial capitals that become huge urban centres of consumption but otherwise there is a societal constraint on city development as new work: in all tribute empires, large and small, urban population never passed 10% of total population (Taylor 2013). However, both empires and cities continued to grow and therefore overall the trend is a gradual increase in the collective large city population (Taagepera 1978; Chase-Dunn and Manning 2002), which keeps Ruddiman's (2010) greenhouse gas anomalies moving forward.

In this period of world-empires the rise in CO 2 ceases rising about 2,000 years ago which Ruddiman (2010, 87) explains by the Boserup effect: we would describe this as being the result of increased urban demand leading to improved agricultural technology and thus a reduction in per capita land cover needs. Apart from this clear change in trend, there are also what Ruddiman (2010, 119) calls ‘CO 2 wiggles', small variations in the overall pattern. He explains these by reference to large-scale disease epidemics and pandemics that, by decreasing the population, lead to less agriculture and therefore cleared land returning to being covered (p. 132-3). However this can be interpreted as a clear case of fluctuations in urban demand: these diseases are disseminated through city networks and their effects multiplied in dense urban populations (similar to diffusions of innovations – see Verbruggen et al (2014, 50-51)).

Traditional world-empires begin to be superseded by the modern world-system in a transition from about 1450 to 1650 (Wallerstein 1976, 2004). A different historical system emerged where the balance between political and economic elites is readjusted in the latter's favour to create a more balanced power relation between cities and states (Taylor 2013). The result is a new release of urban economic development potential. However, at first this effect of the new social relations is not reflected in global urban demand increasing CO 2 levels. The obvious reason is that the modern world-system was initially not global, being focused largely in Europe and the Americas. But there is an effect by this new historical system on climate change – initially, 1600 to 1800, the CO 2 levels actually fell in one of the larger ‘wiggles' (Ruddiman 2010, 87). So where is the reduced urban demand to cause this decline? An explanation can be found in the greatest disease pandemic of all, that which afflicted the Americas after European contact (Ruddiman 2010, 132-133). This decimated indigenous agriculture and the cities consuming the production, both of which have been conventionally under-estimated – Mann (2011) provides an overview of this process; evidence for Amazonia is set out in detail by Clements et al (2015). More generally in European imperialisms, temperate biomass was reduced before the denser tropical biomass leading to later CO 2 and CH 4 rises (Crosby 2004). Thus the great greenhouse increases precipitated by the modern world-system have an important and very clear time lag.

Ruddiman (2010, 171) starts fast anthropogenic climate change conventionally in 1800 and we can link this change symbolically to our argument through the leading cities of the period: in 1800 Beijing, capital of a traditional empire, was still larger than London, but very soon London became the world's largest city through most of the nineteenth century and beyond. In this time China became incorporated into the modern world-system; the latter became fully global by 1900. This is shown in the enormous increase in large city populations indicating a truly qualitative shift to a new world of great cities as recognized at the time (Weber 1899). Thus instead of labeling the social change as simply ‘industrial', the cities approach reinforces Brooke's (2014, 480) argument that the key environmental trigger is immensely heightened urban demand becoming worldwide. For instance, the great urban expansion includes explosive city growth in the frontiers settled by English-speaking peoples as described by Belich (2009; Taylor et al 2010).

However, the urban change in the nineteenth century is more than simply demographic. New ways of living are created. In the modern world, industrial cities changed traditional ways of living into modern clock-based disciplined behaviour in places (factories) and flows (railways). And most important for our argument here, in nineteenth century cities in major countries around the world traditional bourgeois thriftiness morphs into consumption-driven behaviour (Laermans 1993; Dauvernge 2008), as a new way of living (symbolised by the invention and diffusion of the departmental store from the mid-nineteenth century). This behaviour has been inherited and exported as continuously expanding global demand (symbolised by the invention and diffusion of the shopping mall from the mid-twentieth century). This fundamental change in bourgeois behaviour was the consequence of transformation of commerce from being just one element of traditional societies to becoming the dominant feature of modernity as capitalism (Wallerstein 2004, 23-41). This social change finally releases unremitting city economic processes, resulting in spirals of ceaseless capital accumulation requiring ever-expanding consumption as a truly ü ber-demand.

Thus our narrative ends by returning to how it began, the unique human process of social reproduction. It is the ecological implications of ü ber-demanding cities that are toxic. Harnessing non-local sources of reproduction enabled by trading has today culminated in what Jacobs (2000, 119) calls a ‘cultural breaching' of the behaviour necessary to ensure ecological sustainability. She argues that reproduction of any species requires ‘traits which prevent it from destroying its own habitat'. For instance, many large animal species develop behaviours that check habitat destruction – these occupy time that could otherwise be devoted to material reproduction. Seemingly ‘social activities' prevent damage to the environment that would result from continuous grazing by, for instance, elephants, or incessant hunting by, for instance, lions. It is this ‘social' behaviour that prevents full-time exploitation of an environment to its destruction and thereby facilitates reproduction of the herd or pride. Of course, humans have highly developed social behaviours that have checked habitat destruction for most of their existence through reproduction as hunter-gatherers, the leisure-rich ‘first affluent society' as described by Sahlins (2004). But the danger of enhanced non-local reproduction is a very different matter, and a few millennia of cities and a few centuries of capitalism have finally undermined whatever evolutionary safeguards were in place.

Initially, new behaviours were invented in cities to create a vibrant ‘social life' (e.g. guilds were as much social (religious-based) as economic (occupation-based)) but in modern urban worlds the social has been largely enveloped by the economic. Thus the contemporary domination of the social by consumption behaviour (e.g. shopping as prime leisure pursuit) has turned the traditional social time constituted by diversionary protective behaviour into a modern social time constituted by increasingly destructive behaviour. This is the toxic transformation that is being reaped in the twenty first century. Hence message of this narrative is the necessity of transcending our modern heritage.

Conclusion: structural complacency

Having taken Ruddick's (2015) truism on cause and cure seriously, we hope we have shown this cities-climate link to be anything but inconsequential. However our arguments have focused more on the ‘cause' side of the pairing – urban demand - with the ‘cure' being largely latent. In bringing our discussion to a conclusion we begin to rectify this through explicit reference to contemporary climate change policymaking.

In what sense does our narrative offer the new broad canvas for policymaking as promised in the Introduction? At a philosophical level it is an antidote to the modern progress narrative upon which technocratic responses to climate change are based. Technological escape routes that modern ‘time as progress' offers are replaced by spatial concerns for material limits. But our narrative is not another ‘limits to growth' argument since being a unique ‘urban species' means that economic development is at the heart of humanity's existence, its creativity. The latter is premised upon urban demand and limits are being reached because modern creativity is producing an exceptionally destructive outcome: the enhanced urban potential of our times has generated ü ber-demand. But societal handling of urban demand does not have to be this way: our trans-modern thinking has shown that the current toxicity of demanding cities is not inevitable – cities were ‘tamed' in traditional world-empires but at the expense of restricting urban creativity. We cannot afford such a luxury of restraint today; in combating climate change creativity is at a premium. Nevertheless this example does show that urban innovations and their diffusions can create different ways of development. In Soja's (2000) terms we need a fourth ‘urban revolution'. Of course, recognizing and calling for an urban revolution is not original, for instance Brand (2009) sees instrumental opportunities and Brugman (2009) has charted multiple local changes, but our broad canvas points towards a more relational and comprehensive transition centred on city networks.

For us, the crucial point is that to bring cities to the fore in climate change study is to prioritize demand over supply for understanding and tackling climate change. To indicate the immense departure our trans-modern approach is from mainstream thinking we refer to a preeminent textbook, Global Warming: The Complete Briefing (Houghton 2015). Textbooks are special publications that provide the conventional wisdom in a subject area in terms of facts and debates. In this case the book is in its third decade as a fifth edition, qualifying it as sound and popular treatment of its subject. Cities are conspicuous by their absence, which is consistent with lack of the attention given to demand. Although there is discussion of individual responsibilities, when it comes to strategy it is only supply that is directly targeted. Focusing on the UN Framework Convention on Climate Change, it is transport and energy that are to the fore where demand is measured and policy for changing supply developed accordingly. In this self-ascribed ‘complete briefing', there is no interrogation of the demand as collective consumption – how it came about, why it is so large, or whether and by what means change in social behaviour might lead to a reduction in demand.

We can call this structural complacency. States negotiating in UN conferences over supply issues (carbon limits) while the everyday behaviours of billions of people keep the demand ever increasing. By using the adjective structural to describe this policy context, we signal the immense difficulty in overcoming it. There can be no one way, a simple prescription, to combat everyday structural complacency. However, post-normal scholarship and policymaking (Funtowicz and Ravetz 1991; O'Brien and O'Keefe 2014, 60-71)) is an approach for engaging with climate change science and practice that sits comfortably with our trans-modern thinking. It is based on the premise that we can no longer proceed with a problem-solving method where evidence is drawn from recent past experience, and then harnessed to provide a solution. Anthropogenic climate change generates a whole new level of complexity: unprecedented risk at a global scale continually reproduced by myriad actions. Since this process was not created by political (i.e. top-down) policymaking, global, national or local, it will not be ‘solved' by the actions of today's political policymakers. This is not to say that formal policymaking and implementation is irrelevant, rather the sum of these policy ‘parts' can never begin the equate with the ‘whole' need for combatting climate change.

It is now being recognised that cities are actually the most self-sufficient of settlements (Owen 2009; OECD 2012); and furthermore, the larger the city the more self-sufficiency. The key point from our narrative is that this is a direct result of the economic growth generated by import replacement, which is effectively a continual process of economic localization. Localization is a common theme in conventional green thinking wherein localist agendas aim to curtail economic growth (Scharzer 2012; Taylor 2012b). In contrast, import replacement through cities as continual localization linked to innovations and their diffusion generates city networks of development. This combination of local and non-local allows us to posit a fourth urban revolution predicated not on individual ‘green cities' dotted across the economic landscape, but on taming urban demand through dynamic green networks of creative cities, a steady state world economy that is vibrant and therefore appealing (Taylor 2012b).

At this point our argument may appear to have reached a non sequitur : what Jacobs (2000, 84) has referred to as a quest for ‘dynamic stability'. How can green city networks be both steady state and dynamic? Of course they cannot if we continue to think of cities solely in material growth terms; clearly we need to be thinking about cities as more than just mechanisms of economic development. Post-normal thinking has to address rebalancing of the material reproduction with the social. As it happens, treating cities as more than concentrations of economic activity has traditionally been seen as a crucial part in any city's development, making it a metropolitan place combining both work and play. Jacobs (1969) calls this metropolitan development the ‘rounding out' of a city's functions in terms of the social institutions of its times. Hence innovations emanating from cities have always been social and political in addition to economic; for instance, in addition to inventing departmental stores, Victorian cities' are famed for their museums, parks, art galleries and libraries, as well as far reaching public health initiatives. Our argument is that the contemporary domination of the social (i.e. shopping) by the material as ü ber-consumerism needs to be unravelled and a new metropolitan ethos and practice invented.

The utopian goal of the fourth urban revolution is therefore new ways of living based upon social inventions being generated in cities to create new work. The purpose is to maintain a dynamic complex division of labour whilst also regenerating diversionary behaviour that is ecologically protective. Such social and political innovations can be diffused through city networks curtailing material growth by largely substituting today's myriad economic developments by myriad social developments. This is a post-normal vision of a steady-state commercial economy with a vibrant creative society, operating through social-growing cities in dynamic green networks.

ACKNOWLEDGEMENTS

Kye Askins, Michael Barke, Andrew Collins, Richard Kotter and Jon Swords were instrumental in early formation of this work.

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NOTES

^* Peter J. Taylor (email: crogfam@gmail.com), Geoff O'Brien (email: geoff.obrien@northumbria.ac.uk), Phil O'Keefe (email: phil.okeefe@northumbria.ac.uk), Department of Geography, Northumbria University, Newcastle upon Tyne