What if we could cut city energy use by about one-fourth, from 730 EJ to 540 EJ, in 2050? The alternative is tripling it, as current urbanization trends indicate. The most urbanized areas of the globe are North America (82%), Latin America and the Caribbean (80%), and Europe (73%).
Urban areas play a critical role in world climate. The Intergovernmental Panel on Climate Change has found that cities consume up to 76% of global energy and generate about the same percentage of global carbon emissions. Over half the world’s population lives in cities now, and the share is expected to increase to 66% by 2050.
Proceedings of the National Academy of Sciences just published a study by the Mercator Research Institute on Global Commons and Climate Change (a private foundation devoted to science and the humanities, education, and international understanding, concentrating on the European Union) that finds city energy use reduction quite plausible. Mercator plays an active role in activities such as the United Nations Intergovernmental Panel on Climate Change, along with its parent organization, the Potsdam Institute for Climate Impact Research. As well as the Mercator and Potsdam Institutes, colleagues from Yale University and the University of Maryland contributed to the city analysis.
Feeling that aggregate potential for urban mitigation of climate change had been understated, Felix Creutzig and his fellow researchers looked for some hard answers in city energy use. They formulated a “Global Typology of Urban Energy Use and Potentials for an Urbanization Mitigation Wedge.” They discovered that such a wedge does exist and can be widened, although key elements of potential mitigation strategy differ from city to city.
The researchers used data sets from the World Bank and the Global Energy Assessment to model the development of 274 cities, representing 21% of the global urban population and all city sizes and regions worldwide. The population range extends from all the megacities (more than 10 million inhabitants) to a small city of 55,000. From these, they identified eight basic urban types and associated mitigation policies.
New and rapidly growing cities—those in developing nations of Asia, Africa, and the Middle East, in particular—can save the most, because they’re not limited by obsolete infrastructure that locks in high carbon emission patterns. Their potential energy savings in urbanization is 86% of the world’s total potential because they can build in sustainability and green energy policy from the start. Compact urban form and green transport planning can make a huge difference. Changsha in China and Dar es Salaam in Tanzania, for example, can still develop along climate-friendly lines like this.
The research team also identified potential mitigation options in mature, established cities.
“In the U.S., for example, higher fuel prices would enable more compact development in cities like Boulder, Colorado. And in Hamburg, Germany, energy savings can be achieved by connecting low-density development to city centers through public transportation and bike paths.”
Compact urban form is also important in older cities, the researchers say.
The researchers looked at policies on the national scale as well. In countries like Iran or the US, researchers say, raising fuel prices would incentivize a transition toward energy-efficient cities. Higher gasoline prices may not only reduce city energy use by curtailing travel behavior and private vehicle ownership, but they could also affect where people live and work and electricity/heating demand (via modified floor space).
This thought supports a hike in the American motor fuel tax, a subject currently being bandied about in Washington. A new federal transportation bill must be authorized before May 31, when current funding will expire. The gas tax hasn’t changed in more than two decades, and as well as incentivizing energy efficiency, such a move could direct more funds toward alternative energies.
Said Karen Seto, the Yale professor of urbanization and geography who led the IPCC’s urban mitigation group and coauthored this city energy research:
“Our study expands the recent IPCC results by identifying drivers of urban energy use and thus enables effective climate change mitigation strategies across cities worldwide, closing a missing gap of the recent IPCC report…. This paper illustrates that there is a window of opportunity to affect how [rapidly developing] cities develop and save emissions.”
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