Cities as GHG emitters
Cities occupy around 3% of the land’s surface but are responsible for 70% of all carbon dioxide emissions [3]. The disproportionate contribution of urban areas to GHG emissions can partly be attributed to city planning and layout. Most cities tend to have low-density suburban sprawl with limited public transport networks and suburbs often being far away from shops and offices. As such, more people rely on cars which create substantial emissions [4].
As cities concentrate people and activities into smaller areas, they consume large quantities of energy – two-thirds of global energy consumption – by burning fossil fuels and directly contributing to the climate crisis [5,6]. Moreover, the physical urban environment itself is an embodied source of emissions as GHGs are emitted during the construction process as well as during the operational lifetime of buildings.
In addition to the direct use of fossil fuels in urban life, cities import and export goods and services such as food and manufactured goods. The transportation of these goods and services is a large contributor to GHG emissions [7].
The vulnerability of cities to the climate crisis
The vulnerability of cities to climate change is associated with adaptive capacity – the ability to implement measures to reduce vulnerability to the impacts of climate change – of built structures, social structures such as laws and social services such as hospitals as well as the social safety net provided by the state to citizens [8,9].
Research suggests that the most significant effects of the climate crisis on cities are [10]:
- Consequences of sea level rise
- Impact of extreme weather events on infrastructure
- Effects on energy use
- Effects on health
- Effects on resources and water availability
For example, 65% of cities with populations larger than 5 million are located in low-lying areas on or near the coast, making these urban areas vulnerable to sea level rise and storm surges [10]. The direct effects of sea level rise include flooding, land erosion and loss, and direct damage.
Additionally, infrastructure faces the effect of extreme weather events such as storms [10]. Research finds that more than 60% of global cities and the surrounding downwind regions experience more precipitation than surrounding rural areas, and that the intensity of these urban wet islands has nearly doubled in the last twenty years [11].
With an overall increase in global temperatures, there will be a general increase in energy use to keep cool in the summer, and a decrease in energy for heating during the winter. However, this adaptation to climate change may have negative effects on mitigation efforts if the additional energy for the aircon comes from burning fossil fuels.
Climate change impacts human health directly, from the physiological effects of cold and heat – particularly when affected by the urban heat island effect – and indirectly, such as the effect of flooding on the spread of disease [10]. There is also a separate but related rise in the number of cases of climate-sensitive diseases like salmonella [12].
The effect of climate change on water availability will be specific to the region and depend on the relative increases in evaporation and demand for water compared to the amount of precipitation. Cities located in arid areas or regions reliant on snowmelt are most vulnerable to decreases in water availability [10].
The nuances of climate vulnerability
Cities in the Global South are generally more vulnerable to climate change given the existing strains brought about by rapid urbanisation and high population density. [13]. In particular, Africa and Asia are expected to contribute 90% of the projected 2.5 billion increase in global urban population between 2018 and 2050 and have highly vulnerable urban populations with limited adaptive capacity [14].
Economic and social inequality also influences climate change vulnerability [9]. Research shows that individuals with limited access to social and institutional resources and restricted life choices are more vulnerable to climate change losses as they have limited adaptive capacity [9,10]. For example, in many regions girls often leave school earlier than boys to help their mothers. Women are often responsible for procuring food and water through agriculture, which is a major employment source for women in developing countries [15]. This creates disparities between men and women, and as climate change strains agriculture, women may struggle to find a secure income source and resources for their families in their primary role as caregivers in many societies [15].
Reducing the vulnerability of urban cities to climate change requires, as a first step, building their adaptive capacity. This can be achieved in several ways, such as introducing more green spaces, stricter building codes, and investing in the infrastructure of lower-income neighbourhoods [16]. Of course, it is a nuanced issue and the policy and intervention measures will differ from one city to another. In the long term, however, we need to remove fossil fuels from the system entirely [4].
Conclusion
Cities are responsible for a disproportionate amount of CO2 emissions as they are resource intensive, with emissions also embedded in their infrastructure. This makes urban centres more vulnerable to the range of effects of the climate crisis with a more acute effect in the Global South and in vulnerable groups within society. Reducing the vulnerability of urban systems to climate change requires stopping GHG-emitting activities and creating resilient adaptive cities.
