Rethinking our cities so that we can fight climate change.
We are in the middle of a climate crisis, and now is the time to do something. “That’s why it was so sad to see the headline of a report from the Intergovernmental Panel on Climate Change” (IPCC). The report was written by 278 experts, with help from 354 other people. It has 3000 pages and 18,000 references. It is a great example of how science and collaboration can work together. The language used in the document and its summaries isn’t afraid to say what’s on their minds. Despite all the progress that has been made so far, “Without immediate and deep emissions reductions across all sectors, limiting global warming to 1.5°C is out of reach,” the report says.
If we want to keep the predicted temperature rise to a minimum, we need to think about how to do that. This report, on the other hand, only talks about solutions.
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It looks at climate change mitigation efforts that are being used (or have been promised to be used) in everything from farming and transportation to energy supply and manufacturing. There are a lot of different ways to deal with climate change because the causes are many, but humans are to blame for all of them. It will take a multi-pronged approach to deal with it. As excited as you might be about certain technologies, there is no magic “silver bullet” that will solve the problem of climate change.
Chapter 8 of the report only looks at cities. More than half of the world’s people now live in these areas, and that number is expected to rise to almost 70% by 2050. These areas are the source of a lot of the world’s greenhouse gas (GHG) emissions as of 2020, so they make up a lot of the world’s emissions. “As of now, about 100 of the world’s most carbon-intensive cities account for about 18 percent of the world’s carbon footprint.” People who live in cities in “Developed Countries” emit nearly seven times more pollution per person than people who live in low-emission areas.
The only good thing about this is that cities and towns have a lot of ways to cut down on pollution. mitigation efforts that are started in cities can spread to other places and have positive effects on transportation, energy, buildings, land use, and behavior. Even more often, the mitigation efforts of urban areas can spread outward to its surrounding areas and even to other urban areas that are farther away.
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It’s said in this report chapter that urban climate change mitigation fits into three broad strategies: Electrification and switching to zero-emissions resources, as well as green and blue infrastructure, are three ways to reduce energy use in cities. They also help improve carbon stocks and manage flows. There may be a fourth strategy, but it usually comes after the other three have worked well. This is called behavioral change.
What does that mean? What can city planners and managers do in the real world?
Improve the shape and connectivity of cities.
The way we design and build cities has a big impact on how many emissions they produce. Lowest-impact cities have medium to high density housing close to places where people work and shop; they have a rich mix of land uses, a well-connected street network; and they are easy to get to and have short travel times thanks to a variety of transportation options. A “walkable” city has many other advantages, but one of the most important is that it doesn’t produce a lot of greenhouse gas emissions. Carbon lock-in, which happens when “long-lived, energy and carbon-intensive assets stay around for a long time and block out more efficient, low-carbon alternatives,” is less likely to happen in the United States.
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A good example of this is how many cities have a lot of private cars. The infrastructure that cars need (e.g. highways, parking lots) has been given a lot of attention and money over many years. This is not a fact of nature. It has been made even stronger by zoning decisions and urban development patterns. If a city grows through low-density urban sprawl, where homes are far from places of work, education, and entertainment, it forces people to drive. Low-density development is also a big problem when it comes to making new mass transportation options.
Established cities that are spread out and rely on cars are likely to have more per capita emissions than compact, walkable cities. Isn’t it hard to get out of this? It’s not, but there are ways. It requires a lot of planning and decision-making, a lot of money for public transportation, and new and better mixed-use neighborhoods.
The report’s authors say that “new and emerging cities have an unmatched ability to become low or net zero emissions urban areas while still having a high quality of life,” which is what the report is about. This is because new cities don’t have to tear down or replace old infrastructure. Instead, they’re still putting together the building blocks that make up a city. They can make better, more environmentally-friendly decisions about everything from how they build things to where they put their money.
Rethink how you use energy.
In a lot of cities, replacing fossil fuel-based technologies with electric ones is already making a big difference. Electric rail, trams, buses, and vehicles are now common in most places, and they’re becoming more common in other places as well. That’s not all. In order to be truly effective, decarbonization needs to be done all over the place. A way to keep carbon from getting stuck in fossil fuels is to use waste heat or renewable energy instead of putting it in fossil fuels. In the same way, replacing gas-based heating and cooling with electric heating and cooling networks and heat pumps in homes and businesses can also help. District-wide systems work best in areas with a lot of people. In some cases, the switch can cut an area’s carbon footprint by 65%.
Smart (and distributed) electric grids are also allowing for a more environmentally friendly way to get and use electricity. These grids don’t just make electricity in one place and send it to customers. They have “bi-directional flows of electricity and information between generators and customers.” Citizen-managed utilities, community batteries, and a peer-to-peer trading infrastructure can support this development.
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Of course, in order to be truly “green,” a grid must use electricity that comes from renewable sources. Roof-top photovoltaics (PVs) and all-electric cars alone could cut CO2 emissions by up to 95 percent, according to several studies (e.g.1, e.g.2).
They can keep future carbon emissions down by making cities more compact, and keeping green and blue assets that are already there. If they didn’t want to use fossil fuels, they could go straight to electric power for everything from transportation to cooking to heating to cooling. Then, instead of getting rid of informal settlements at a big financial and environmental cost, they could be regenerated and improved by investing in things like energy management, water supply, and wastewater treatment at the neighborhood level.
Construct in a circular way.
Demand for construction materials has gone up a lot in the last two decades. A lot of this has been caused by rapid urbanization in China, but it is a global trend. As cities get bigger and more dense, there is a bigger need for buildings and infrastructure. The materials that are most commonly used in mid- and high-rise urban construction, such as concrete, steel, aluminum, and glass, all have a big carbon (and environmental) cost, even though they have been getting more efficient over time. When it comes to materials, “27 billion tonnes (Gt) in 1970 turned into 89 billion tonnes in 2017.” This is what the OECD says. It will double even more by 2060.
The materials supply chain and the construction, operation, and demolition cycle have been rethought in a big way by many people because of these changes. They think that part of the answer is to make the urban landscape so that it can go around and around again. It would be better if we learned how to use cities as a material bank to build new cities in the future. When I travel, Prof. Daniel Hall told me to keep track of where materials have been and how they’ve been processed. “In the same way that I get a stamp in my passport each time I stop somewhere, materials can also get a record of where they have been, how they have been processed, and other information attached to them,” he said. … When the building is harvested later, you’d have a clear record of all of its parts and how they worked together.
Another option is to replace the most energy-intensive materials stocks with less energy-consuming ones. A specific example in the IPCC report is the use of engineered wood instead of steel in mid-rise buildings in cities. This is something I first wrote about a few years ago. The authors say that it could “transform cityscapes from their current status as net sources of GHG emissions into large-scale, human-made carbon sinks.” Between 2020 and 2050, 2.3 billion people will live in cities, and building with wood could store between 0.01 and 0.68 Gt CO2 per year, depending on a number of factors, like the average floor area per person.
Of course, only if working forests are managed and harvested in a way that doesn’t harm the environment will biomass-based building materials be a good way to fight climate change. To do this, there will need to be better forest and urban land governance and management policies. It will also need something that is being talked about more widely in the construction industry: carbon accounting methods that are internationally agreed upon. The hope is that giving natural resources a value in money will make them more likely to be used for forest restoration, afforestation, and sustainable forestry.
Pave cities with green and blue.
We’ve talked about both green and blue infrastructure a lot in this column, so you may not be surprised to see them again here, either. All of these things can be found in parks, trees on the streets, gardens on top of buildings and more. They can also be found in greenways, nature reserves, wetlands, and sustainable urban drainage systems. A system like this can also protect cities from floods by storing carbon and lowering city temperatures, which lowers the amount of electricity buildings use to run them. Green-blue infrastructure has a lot of other benefits, too. For example, it helps biodiversity, improves air quality, and makes public spaces more accessible for city dwellers, which can lead to better health for people.
On a per tree basis, urban trees have the most power to fight climate change through carbon sequestration and less energy use in buildings, according to the IPCC chapter on urban trees. It already stores about 7.4 billion tonnes of carbon in urban trees around the world, but if all of the plantable (non-tree and non-impervious) space in our cities were turned into trees, that carbon storage value could almost triple.
Change your behavior.
We’re told all the time that our own actions have no effect on reducing the effects of climate change. While it’s true that corporations and governments have to do a lot of the work to make big changes, we can and do make a difference. One way to do that is to cut down on your transportation emissions. Yes, you can work from home some days. Is it possible for you to take the train, walk, or ride a bicycle? Maybe you could share a car with a neighbor. Taking less flights also helps. Home energy use: Can you improve your insulation or use more efficient appliances? You could also turn down your thermostat. If you change your behavior in all areas (e.g., transportation, buildings, food, etc.), you could reduce your GHG emissions by 5.6–16.2 percent compared to a baseline of GHG emissions that you’ve already had for your whole life.
They make it easy and convenient for people to change their behavior. So get involved in lobbying your local representatives, and vote for people who care about the environment when you go to the polls. Make sure they know that you want more walkable neighborhoods, more money for renovations and energy-saving retrofits, and easier access to sustainable modes of transportation.
In the end, there’s no simple answer. But we can’t wait any longer to act. Climate change is a direct result of more than a century of people not paying attention to warnings and not using resources in a way that is safe. The next few years are very important in changing that. Hoesung Lee, the head of the IPCC, said that “the decisions we make now can help us have a better future.” We have the tools and know-how to keep the temperature from rising.
