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To maintain a fighting chance of limiting warming to 2 degrees C, global emissions need to peak this decade, and then decline steadily and rapidly to roughly 1 ton per person annually by the middle of the century.  Globally, we’re currently at 6 tons per person.  The U.S. is at 23.  China, the world’s most populous nation, is also at 6, and growing about 10% per year.  We need to bend the curve, and fast.

We critically need to restructure our energy system.  Out with fossil fuels, in with renewables. Use less energy in buildings and factories.  Create low-carbon transportation. Easy, right?  Beyond that, well… it gets (even) harder.  

An increasingly prevalent notion is that one major climate solution is close at hand but often overlooked: the city.  The world is rapidly urbanizing, with nearly 70% of the world’s population expected to live in urban areas by 2050.  The way that cities are built and rebuilt can (in part) determine the greenhouse gas footprint of their residents.  If we channel the global migration to (and growth within) cities into low-carbon development, will it help?

The shape and layout of cities has particular sway over emissions from resident transportation.  Cities that provide residents ready access to goods and services through proximity rather than extensive networks of cars, roads, and parking lots lead to lower carbon emissions.  When home, shopping, work, school, and entertainment are all close by, car trips are fewer, and shorter.   Looking across cities, as population density goes up, auto travel, and associated greenhouse gas emissions go down.   The difference is up to 5 tons per person compared to the most sprawling regions: say, between Denver (with over 6), to New York City (with less than 2), to Barcelona (with about 1).   By building up, and filling in, cities create the conditions where walking, biking, and public transit can take the place of car trips.  Of course people have to want to live in these cities, and these neighborhoods.  Urban “grain” and vibrant streetscapes hold human interest, which tends to mean a mix of uses and building types rather than monolithic skyscrapers.

Building cities that are, on average, denser, also brings other energy and greenhouse gas emissions benefits.  Apartment buildings, with their shared walls and economics of scale, need less energy to heat and cool than detached houses.  And smaller homes have less room for lots of furniture and stuff, meaning fewer goods are needed, avoiding the emissions associated with making these goods.  Of course, accommodating growth within existing cities through in-fill development also helps avoid emissions associated with clearing new land for development.

Taken altogether, how much do denser, pedestrian- and transit-friendly cities reduce greenhouse gas emissions relative to the alternative?  It’s an elusive question, and a complicated one.  Even if a city enabled emissions associated with resident transportation and housing below 1 ton per person (an ambitious goal in itself, and one that Seattle is exploring, that wouldn’t help much with the emissions associated with other stuff we still buy, including food.   And what if giving up the car, and downsizing the home, means more money to spend on (perhaps even more climate-damaging) airplane trips, as has been shown to happen in at least one city?  

People are moving to the city, especially in developing countries, by the millions – even billions. How that growth gets accommodated has a significant impact on how greenhouse gas emissions-intensive cities will be (not to mention other, critical local issues, such as health and safety of housing the new residents, many of them desperately poor.)   Will global cities sprawl, locking in car use for decades to come, or create vibrant, people-focused places?  

By their very nature, cities can provide an important piece of a low-carbon future if they can orient us towards low-carbon lifestyles.  It’s clear they can do this for buildings and (especially) transportation, and for this reason they should be a central piece of the discussion about how to rapidly reduce global greenhouse gas emissions.  Whether they can be a crucial lever for emissions from other parts of the economy – such as from food, or industry – is an entirely open question.  

Peter Erickson is a Staff Scientist in the Climate and Energy program in the Seattle office of the Stockholm Environment Institute. His research focuses on climate change policy, with particular interests in the role of offsets in cap-and-trade programs, contribution of consumption and behavior change to reducing greenhouse gas emissions, industrial policy, and cities.

Originally posted to Climate Change SOS on Tue Aug 21, 2012 at 02:00 PM PDT.

Also republished by J Town and Ecocities Emerging.

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Comment Preferences

  •  Access by proximity (7+ / 0-)

    I think is one of the most effective ways to lower our ecological and carbon footprints. I'm really glad to see the UN getting serious about cities, because I think that by restructuring our cities to function more like ecologically healthy systems we can alleviate a whole range of problems, including climate change.

    But how to measure and find indicators as to how far along a city has come? Check out the International Ecocity Framework & Standards initiative that addresses these questions and is now being given serious consideration by the UN.

    Thanks you so much for this post, I'm so glad your voice and the issue of cities is part of this blogathon.


    Hope is not the conviction that something will turn out well, but the certainty that something makes sense regardless of how it turns out. - Vaclav Havel

    by citisven on Tue Aug 21, 2012 at 02:38:19 PM PDT

  •  your last paragraph is an interesting one. (5+ / 0-)

    one of things about cities is the access to "land intensive" quantities like food and raw materials.  One of your references (here) suggests that the additional upstream costs (in GHG output) are significant.  

    I'd like to see more on the total GHG cost of our highly organized urban living/ag/resource operations.  It'd be very interesting to see how much we can improve on energy use and whether or not we can de-industrialize agriculture.  Mining for non-energy resources vs. recycling metals and other mined resources could also be an important solution component.

    Thanks for the post!

    Who names their pony Monty?

    by bubbanomics on Tue Aug 21, 2012 at 02:44:33 PM PDT

  •  Thank you for posting this excellent diary. (5+ / 0-)
    Even if a city enabled emissions associated with resident transportation and housing below 1 ton per person (an ambitious goal in itself, and one that Seattle is exploring, that wouldn’t help much with the emissions associated with other stuff we still buy...
    Lifestyle changes especially in the area of consumerism must  concurrently happen.   I love this quote from 1994.

    Mr. Paul R. Ehrlich is Bing Professor of Population Studies and Professor of Biological Sciences at Stanford University.  He states the following regarding our consumerism and its impact on our planet.


    "The United States poses the most serious threat of all to human life support systems. It has a gigantic population, the third largest on Earth, more than a quarter of a billion people. Americans are superconsumers, and use inefficient technologies to feed their appetites. Each, on average, uses 11 kW of energy, twice as much as the average Japanese, more than three times as much as the average Spaniard, and over 100 times as much as an average Bangladeshi.

        In all, humanity's high-energy activities amount to a large-scale attack on the integrity of Earth's ecosystems and the critical services they provide. These include control of the mix of gases in the atmosphere (and thus of the climate); running of the hydrologic cycle which brings us dependable flows of fresh water; generation and maintenance of fertile soils; disposal of wastes; recycling of the nutrients essential to agriculture and forestry; control of the vast majority of potential crop pests; pollination of many crops; provision of food from the sea; and maintenance of a vast genetic library from which humanity has already withdrawn the very basis of civilization in the form of crops and domestic animals."

    Americans are still superconsumers.   Our society is going to have to come to terms with the fact that we can no longer afford to have and consume everything our capitalist system is capable of producing.  

    If we really want to straighten out all this crap we need to really think about shit!

    by John Crapper on Tue Aug 21, 2012 at 02:44:52 PM PDT

  •  Pete is in Idaho with limited internet access (1+ / 0-)
    Recommended by:

    and he will be checking in at a later time to comment.

  •  There was some information in this that (0+ / 0-)

    I haven't seen before:

    To maintain a fighting chance of limiting warming to this amount, global emissions need to peak this decade, and then decline steadily and rapidly to roughly 1 ton per person annually by the middle of the century.  Globally, we’re currently at 6. The U.S. is at 23. China, the world’s most populous nation, is also at 6, and growing about 10% per year.  We need to bend the curve, and fast.
    Very interesting. Thanks for posting.
  •  Urban areas can also grow food (0+ / 0-)

    There are wonderful pilot projects in many cities, from rooftop gardens to replacing lawns around schools and churches to indoor greenhouses to edible landscaping. Oh, and backyard chickens and even goats. It would be hard to grow enough to feed an entire city 100%, but not hard to make a considerable contribution -- while lowering carbon and sequestering it in the soil via composting, and of course reducing the transportation to bring food from around the globe.

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