The global urban condition and politics of thermal metabolics: The chilling prospect of killer heat

Simon Marvin


Under conditions of climate change and continued urbanisation, one of the critical challenges of the twenty-first century will be to manage thermal metabolism in ways that sustain urban life during extreme heat events. Advances in microclimatic knowledge and expertise, emerging landscapes of novel thermal socio-technical infrastructures and new forms of digital weather monitoring and control are emblematic of this shift. Together, they reflect a new logic of re-engineering of the outside environment through fixed and permanent thermal infrastructures designed to protect against too much (or too little) heat with the aspiration of producing ‘perfect weather’ all year round. The drive is not simply to provide ‘comfort and convenience’ during heatwaves, but it becomes increasingly critical to secure urban life within safe limits through thermal modification. The chapter charts these developments and asks more critical questions about the social implications of thermal modification. Why has urban thermal metabolics become so important? What sorts of cities are investing in thermal modification? Who will be included or excluded from the thermal effect of these new capacities, and do they represent new forms of urban socio-spatial advantage and disadvantage that weakens protection for the less affluent? What are the wider socio-ecological implications of urban thermal engineering?

Overheating and urban thermal metabolism

Thermal management of the outdoor environment will become as critical to supporting urban life as air-conditioning has been to enabling urbanisation to transcend climatic limits by standardising indoor environments (Healy, 2008).There are three well-understood and researched sets of factors - that due to space we can only briefly consider here - whose complex intertwining can help account for the emergence of an intensified problematic of urban overheating (see Rikards, 2019 for a review).

The first is climate change that is already leading to significant temperature rises of 1,5°C that dramatically increase the intensity, frequency and duration of extreme thermal events. Critically, these changes will increase the scale of coverage and the variability of extreme heat events to affect many more urban areas. Life-threatening heatwaves are expected to escalate from being exceptional to normal and regular events. The second is that the implications of these global and regional changes are amplified by urbanisation.The Urban Heat Island (UHI) is how urban climatologists understand the ways in which the urbanisation process itself- through removal of vegetation and introduction of hard surfaces - reshapes urban microclimates to the extent that the heat in urban areas is typically much higher than surrounding areas. There are also dramatic differences in temperatures within an urban area. This ‘ratcheting up’ effect of the material conditions of the urban environment creates much higher temperatures than would otherwise be the case - that can kill humans, animals, plants and result in technical failures of key equipment and essential infrastructure. The third factor is the structural differences in the ability of urban populations to cope with extreme heat (see Klinenberg, 2002). Poor-quality housing, absence of air-conditioning, lack of greenery and trees, low mobility and poor health all greatly exacerbate and intensify the destructive consequences of heat extremes on urban populations. Typically, low- income and black communities disproportionality suffer from the effects of heat events - they also have severe consequences for outdoor workers, the elderly, the ill and children who cannot easily cope with the effects of extreme heat.

This changing context means there is an urgent need to extend research interests into analysis of urban thermal metabolisms (see Capriotti and Romanowicz, 2013). The challenge is to construct an understanding of the material and social intertwining of both the urban environment and the circulations of heat. A urban thermal metabolic framework could be constituted through

  • (i) knowledge and understanding of the physical heat inputs, sinks and outputs and its spatial and temporal variability in configuring the differential exposure of humans and materials to heat;
  • (ii) the analysis of the social, material, ecological, technological and economic interrelationships that contribute to the production of particular thermal environments at multiple scales, and; (iii) unpacking the differing political contexts through which the thermal environment is constituted as both a problem and an object of intervention focussing in particular on the social and ecological inequalities that may be concealed (or revealed) by these responses. Whilst this short chapter cannot address all these issues, we explore the contours of an emerging urban thermal politics and in doing so highlight what is at stake for the future development of global urban studies.
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