www.buildingsandcities.org/insights/commentaries/cities-planning-heat.html

By Rohinton Emmanuel (Glasgow Caledonian University, UK)

Urban warming creates a 'double jeopardy' on a majority of humans (urban heat island and global warming). Sufficient information exists to identify where local action is most needed to protect those who are most vulnerable. As a matter of urgency, COP-26, national governments and local authorities need to address heat vulnerability by identifying vulnerable areas and implementing changes in planning practices.

Along with providing more irrefutable proof of the anthropogenic causes of global warming, the recently released 6^th Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC, 2021) also highlighted the nexus between urbanisation and microclimate and their superimposing effects with global and regional warming. AR6 concluded that 'there is very high confidence that future urbanization will amplify the projected air temperature warming (in cities) irrespective of the background climate' and the effect on nocturnal warming 'could be locally comparable in magnitude to the global GHG-induced warming' (IPCC, 2021: 10-115). Urban growth further exacerbates the possibilities for increases in the frequency and magnitude of extreme events such as heatwaves.

What can municipalities and urban planners do to address this challenge? A key consideration for adapting to climate change is the impact at the microscale: the microclimate which is influenced by local surroundings and climate context.

Planning action has a vital role to anticipate and adapt to climate change especially the microclimate element as this impacts on individual dwellings, buildings and outside spaces. We must now actively engage with this because urban built form evolves slowly over time. We must ensure that climate change does not exacerbate existing inequalities but act in a manner that equitably distribute the climate change burden.

The good news is that the same variables that lead to local warming (i.e. the way land is used and covered, the configuration (massing) of buildings relative to each other and in relation to streets, the thermal properties of building materials and pollution from human activities, see Emmanuel, 2021) could also be used to map heat vulnerability. Even in the absence of detailed local climate information, such mapping could highlight local areas of relative heat vulnerability at a fine enough scale for planning action to mitigate the negative consequences of local climate change.

Figure 1 shows such an approach to local scale heat vulnerability mapping in Glasgow, the host city of COP-26. No additional data was needed to create such a heat vulnerability map: existing census data on population, climate and land use were used. Super-imposing this on socio-economic conditions in the city ('deprivation' data) gives a first order indication of where vulnerability is at its highest and where adaptation action is most needed.

Thus, we have the data and tools to map where the vulnerabilities are at their greatest (as shown in Figure 1) as well as where these are mostly clustered (Figure 2). Utilising this knowledge would help prioritise interventions and also identify where 'more bang for the buck' are likely. The inclusion of socio-economic conditions will foster equitable transition to a climate resilient future.

What is now needed are planning processes finely attuned to local realities to achieve the desired change. These could take the form of wind corridors for natural ventilation, judicious use of waterbodies and green infrastructure to reduce humidity levels, shading arrangements using built massing as well as green infrastructure, provision of shaded and well ventilated open space, as well as building level strategies where relatively modest alterations could lead to significant reduction in heat risk.

While we await intra-national, cross-border structural changes to limit GHG emissions as ultimate mitigation measures arising from COP26, equal emphasis is needed on these relatively low-cost, local adaptation actions that bring about immediate relief to urban dwellers. Given the uncertainties of local climate information, reversibility of local adaptation actions will greatly enhance resilience and nature-based solutions are particularly suited in this regard

References

Ananyeva, O. (2021). Green infrastructure cooling strategies for urban heat island mitigation in cities: case study of Glasgow City Centre, in R. Emmanuel et al. MUrCS Proceedings 2021, LAB University Press, Finland (in press)

Begum, R. (2021). A critical evaluation of different methods of urban climate mapping: a case study of Glasgow, in R. Emmanuel et al. MUrCS Proceedings 2021, LAB University Press, Finland (in press)

Emmanuel, R. (2021). Urban microclimate in temperate climates: a summary for practitioners. Buildings and Cities, 2(1), 402-410. https://doi.org/10.5334/bc.109

IPCC (2021). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. https://www.ipcc.ch/report/ar6/wg1/#FullReport

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