Urban climate sustainability and why it’s essential

Urban climate sustainability is one of today’s biggest global challenges.  Despite occupying just 3% of the earth’s total land surface, cities are home to over half the world’s population and they account for approximately 70% of global greenhouse gas emissions.

This concentration of individuals, businesses and infrastructure has made those areas urban nerve centres for innovation and development, but such spaces are also highly vulnerable to the impact of climate change.

Key strategies for urban climate sustainability

Current climate dynamics are already having tangible effects: higher average global temperatures, with increasingly frequent extreme heatwaves, regular intense weather events and rising sea levels directly affecting citizens’ quality of life.

Heat islands (a phenomenon caused by the concentration of impermeable, dark coloured surfaces such as tarmac and cement combined with a lack of vegetation) in particular, further exacerbate the effects of global warming, making cities several degrees warmer than the surrounding areas.

In this context, it is not sufficient to limit urban climate sustainability efforts to specific measures; a comprehensive approach also encompassing mitigation and adaptation is now required.  This means reducing emissions, improving energy efficiency, rethinking transport models and developing strategies to boost the resilience of urban populations faced with now inevitable extreme weather events.

Cities have access to a wide range of technical strategies and policies designed to deal with the challenges of climate change.  These can be grouped into three categories, as follows.

• Nature-based solutions, (NbS)

NbS are based on the use of natural processes and resources to mitigate the impact of climate change.  The most effective include:

• more green spaces in urban areas: parks, vertical gardens, green rooves and walls can help to lower temperatures, improve air quality and manage rainwater;
• urban and peri-urban forests: increase CO₂ absorption capacity and provide shade, helping to counteract the heat island effect;
• blue infrastructures: artificial lakes and rainwater collection systems improve hydrological resilience and reduce the risk of flooding.

• Technological and architectural innovation

Urban sustainability requires resilient buildings and infrastructure with elevated energy performance levels and smart building management systems such as:

• nearly-zero energy buildings (nZEBs), with advanced thermal insulation, integrated solar panels and natural ventilation systems;
• reflective rooves and surfaces, which can lower internal temperatures, reducing the need for artificial cooling systems;
• smart grids and energy accumulation systems, allowing for optimised energy production and consumption management.

• Multilevel governance and integrated policies

Cities cannot function in isolation, as urban climate sustainability requires multilevel governance which combines national, regional and local policies.  Key elements include:

• resilient urban planning, with up-to-date building regulations and financial incentives for sustainable construction;
• community participation to ensure the introduction and widespread use of sustainable practices;
• international cooperation, necessary for the transfer of knowledge, technologies and economic resources.

Climate vulnerability of African cities

The African continent now represents an epicentre of critical urban climate challenges.  Some of its cities are among the fastest-growing in the world and its population is expected to double by 2050.

This rapid growth often happens due to the absence of adequate infrastructure, with large proportions of the population living in makeshift housing, which lacks essential services and is particularly exposed to environmental hazards.  The (already apparent) increase in temperatures is causing extreme heatwaves with dramatic consequences on health.

Productivity is compromised, especially in sectors where people work outdoors, while food security is threatened due to significant losses in the agricultural sector.  According to international forecasts, over a billion people could find themselves facing conditions of extreme climate vulnerability by the year 2050.

A key priority for African cities is therefore the development of sustainable cooling systems.  Increasing reliance on traditional air conditioning systems associated with elevated energy consumption and emission levels threatens to exacerbate the vicious circle of energy demand, emissions and global warming.

This has led to the launch of initiatives promoting passive, nature-based cooling solutions.  One example is the BeCool programme, developed in Asia and subsequently adapted for use in Africa.  The key measures it includes are:

• reflective rooves and specialised paints, capable of reducing the internal temperature of buildings by up to 4°C;
• natural ventilation and bioclimatic design, using air currents and architectural positioning;
• strategic green spaces, which create cooler urban microclimates and improve thermal comfort.

As well as reducing reliance on artifical cooling systems, these solutions also provide environmental and financial co-benefits.

Solutions and future outlook

The African response to the urban climate crisis involves not only technological solutions, it also extends to public policy.  Some countries have already started to include sustainable cooling measures in their national climate plans:

• Somalia: has included sustainable cooling in its new Nationally Determined Contributions (NDCs);
• Kenya: is updating its building regulations, introducing specific requirements for resilient, sustainable construction;
• South Africa: urban centres like Cape Town have requested greater financial and political support in order to implement urban adaptation strategies.

These examples reflect growing political awareness, as well as the indispensible need for strong international support to ensure the measures are put into place.

Technical meetings and multilateral talks held in Africa have underlined the importance of building alliances between governments, international organisations, the private sector and local communities.  Strengthening international partnerships and financial mechanisms is considered essential to allow African cities to take the lead in their own climate innovation processes.

The outlook suggests that the African experience will play a decisive role in establishing technical and political guidelines in the region, bringing greater coherence between national strategies and local action plans.  If adequately supported, cities in that part of the world could transform their current vulnerability into an opportunity, to become global models of resilience and climate sustainability.

Translated by Joanne Beckwith