Environment, Energy and Nature

Radical urban transitions needed to avoid dangerous global warming

4 min


Catlyne Haddaoui and Seth Schultz

The special report by the International Panel on Climate Change warns that radical social transformation is essential to avoid a global temperature rise beyond 1.5⁰C. This column focuses on the need for decarbonization of towns and cities, which will require higher population densities, and action across the housing, transport, and waste sectors, as well as energy and industry. Urban partnerships around the world are taking bold and aggressive action to reach carbon neutrality by 2050, but leadership from national governments is crucial for achieving the transition to sustainable cities at the right speed and scale.

Remember when we thought that buying a car that got over 30 miles to the gallon and unplugging your TV would solve climate change? Well, brace yourself because the IPCC special report on global warming of 1.5⁰C just crushed those hopes.

The report published by the world’s leading climate experts is alarming: we won’t be able to avoid a global temperature rise beyond 1.5⁰C without a radical transformation of our societies.

What needs to change?

The International Panel on Climate Change identifies four systems that need to be urgently transformed to avoid dangerous levels of global warming: energy, land use, industry, and cities.

In the energy sector, switching to renewable sources and improving efficiency will be a big part of the answer. Carbon capture and storage are also identified as crucial in almost all scenarios – although no one has yet figured out how to make those processes work cost-effectively at scale.

In the land use sector, sustainable intensification of agriculture, better irrigation and ecosystem restoration are recommended to reduce greenhouse gas emissions. Conserving forests and wetlands is particularly important because they are such carbon-rich ecosystems.

In the industry sector, energy efficiency, recycling and low-carbon fuel sources are the most important options for climate change mitigation. Industries such as cement and steel have particularly outsized carbon footprints, and therefore need to decarbonize fastest.

All of these three systems intersect in towns and cities, where an increasing proportion of the world’s population live, with estimates predicting 70 million new urban residents per year until mid-century. Indeed, the urban system must be transformed – and transformed rapidly – if the world is to reach net zero emissions by mid-century.

How should urban systems change?

Research shows that dense cities tend to emit significantly less greenhouse gases than their sprawling counterparts, among other benefits. Pursuing more compact urban forms is central to reducing emissions.

This is primarily because the shape of cities determines the transport choices of urban residents. Higher population densities, mixed land use, and good connectivity can all reduce the need for individual, motorized transport.

Compact urban growth can also decrease the heating and cooling needs of buildings, and reduce the pressure on surrounding ecosystems, since less land needs to be converted to urban purposes. This can reduce the emissions from deforestation and other changes in land use.

But decarbonization of towns and cities will require more than just higher densities. Reaching net zero urban emissions will require action across the housing, transport, and waste sectors, as well as energy and industry.

Who can drive the urban transformation?

Cities around the world are already taking bold and aggressive action on climate change by developing plans to reach carbon neutrality by 2050. That said, ambitious decarbonization of urban systems will require action by a whole range of partners in addition to local governments from private firms to community organizations. Many are already making major commitments.

But leadership from national governments is crucial to achieving the transition to sustainable cities at the speed and scale required.

First, national governments have a key role to play in establishing enabling policies. By implementing policies and incentives that directly or indirectly affect urban areas, central governments can influence their shape, their energy efficiency or their air quality. Building codes, for example, are an important tool for national governments to move cities towards more sustainability by encouraging mixed land use, compactness, and energy efficiency.

Second, national governments can unlock massive funding for sustainable urban infrastructure. All countries need large-scale investment in urban systems, whether to refurbish established infrastructure to reduce its embedded emissions, or to build new lower-carbon infrastructure where there is currently a deficit. Only national governments have the fiscal capacity required to raise and steer finance at sufficient scale.

Finally, national governments need to coordinate efforts and actions from the many actors contributing to the low-carbon transition. In particular, central governments can clarify and enhance the roles and responsibilities of sub-national governments, ensuring that they have the skills and resources to fulfill their mandates. National governments can further stimulate the generation of knowledge and innovation to fuel this transformation through strategic research programs.

The IPCC report reminds us that – without this ambitious and crosscutting action – we will see the catastrophic effects of climate change in every country and every city. Every supplementary 0.1⁰C puts our planet at greater risk. Cities warm more dangerously, coastal areas face greater risk of flooding, and drylands face more serious water scarcity.

As an example, at 1.5⁰C, twice as many megacities – and 350 million more people – will become heat-stressed by 2050. Doing everything we can to hold to 1.5°C is our only chance to limit the impact of even greater climate extremes and disasters.


Catlyne Haddaoui
Research Analyst for the Coalition of Urban Transitions
Seth Schultz
Special Advisor to the Global Covenant of Mayors on Research & Innovation