Keeping cities green: Avoiding carbon lock-in due to urban development

Cities around the world are emerging as leaders in the fight against climate change, embracing low-carbon transport, high-efficiency buildings, renewable energy and other strategies to reduce emissions while building more vibrant urban communities. At the same time, urban areas are growing astoundingly fast: 1.4 million new urban dwellers each week, and with corresponding demands for energy, goods, and services. Therefore, how our cities are built is a critical factor in the intensity of urban energy use. From the types of housing and commercial buildings, to our road networks and transport systems, to how we get our heat and power, urban infrastructure determines, to a great extent, whether a city has high or low greenhouse gas emissions.

This paper looks at two scenarios of urban development over the next 15 years. It finds that, in the reference scenario, new, energy-inefficient urban development may substantially “lock in” future CO₂ emissions, as roughly 30% of future CO₂ emissions “committed” annually occur due to new, urban building and transport systems. However, in an aggressive “urban action” scenario, urban policy-makers can instead deploy the most energy-efficient technologies and urban design, and avoid committing about 45 Gt CO₂ of cumulative future emissions.

Making these choices now, instead of attempting costlier retrofits later, can substantially lower the cost of meeting stringent climate objectives for cities and nations alike. At the same time, retrofitting of existing infrastructure – urban and otherwise – is also necessary to “unlock” the existing roughly 800 Gt CO₂ of emissions already “committed” and help keep emissions within the 1,000 Gt CO₂ carbon “budget”.

Download the paper (PDF, 1.7MB)