Climate Change: a global commons problem

The report published week before last by the Intergovernmental Panel on Climate Change (IPCC) has made it clear that climate change is a global commons problem. The solution is to decouple rising temperatures from economic and population growth. Hundreds of the most prominent scientists with divergent political views from around the world have run thousands of scenarios, and I’m going to take a moment here to extract some of the land use issues woven through the report.

This is practical advice for city planners about how to move in a cleaner direction and pull as many local decision-makers as possible along with you. So “wonk alert” to our less technically interested readers, who may prefer this Yale 360 piece from prominent enviro thinkers about paths forward. Or this older piece by Emily Badger in Atlantic Cities about how reformatting the single family home’s relationship to its neighbourhood will help.

Strategies Related to City Planning in the IPCC Report

“Globally, economic and population growth continue to be the most important drivers of increases in CO2 emissions from fossil fuel combustion. The contribution of population growth between 2000 and 2010 remained roughly identical to the previous three decades, while the contribution of economic growth has risen sharply.” – IPCC

The impacts of how developing nations lay out and expand their cities is an important dialogue. A few inspiring plans come to mind, including some of Dhiru Thadini’s urban designs in India and Peter Calthorpe’s city plans in China.

Vedanta University Plan, credit: Ayers/Saint/Gross Inc. Architects + Planners

Vedanta University Plan, credit: Ayers/Saint/Gross Inc. Architects + Planners

For all of us, compact, walkable, mixed-use patterns are essential, and the emergent science of Eco-Districts is helping with infrastructure finance. DPZ’s work on Reinvent Phoenix is breaking new ground, supported by a large team of us, including Center for Neighborhood Technology and Crabtree Group.

“Mitigation options in urban areas vary by urbanization trajectories and are expected to be most effective when policy instruments are bundled. Infrastructure and urban form are strongly interlinked, and lock‐in patterns of land use, transport choice, housing, and behaviour. Effective mitigation strategies involve packages of mutually reinforcing policies, including co‐locating high residential with high employment densities, achieving high diversity and integration of land uses, increasing accessibility and investing in public transport and other demand management techniques.”

The largest mitigation opportunities with respect to human settlements are in rapidly urbanizing areas where urban form and infrastructure are not locked in, but where there are often limited governance, technical, financial, and institutional capacities. The bulk of urban growth is expected in small‐ to medium‐size cities in developing countries. The feasibility of spatial planning instruments for climate change mitigation is highly dependent on a city’s financial and governance capability.”

“Thousands of cities are undertaking climate action plans, but their aggregate impact on urban emissions is uncertain. There has been little systematic assessment on their implementation, the extent to which emission reduction targets are being achieved, or emissions reduced. Current climate action plans focus largely on energy efficiency. Fewer climate action plans consider land‐use planning strategies and cross‐sectoral measures to reduce sprawl and promote transit‐oriented development.

“Successful implementation of urban‐scale climate change mitigation strategies can provide co‐benefits. Urban areas throughout the world continue to struggle with challenges, including ensuring access to energy, limiting air and water pollution, and maintaining employment opportunities and competitiveness. Action on urban‐scale mitigation often depends on the ability to relate climate change mitigation efforts to local co‐benefits.

“The transport sector accounted for 27% of final energy use and 6.7 GtCO2 direct emissions in 2010, with baseline CO2 emissions projected to approximately double by 2050.”

Technical and behavioural mitigation measures for all transport modes, plus new infrastructure and urban redevelopment investments, could reduce final energy demand in 2050 by around 40% below the baseline.

“Mitigation strategies, when associated with non‐climate policies at all government levels, can help decouple transport GHG emissions from economic growth in all regions. These strategies can help reduce travel demand, incentivise freight businesses to reduce the carbon intensity of their logistical systems and induce modal shifts, as well as provide co‐benefits including improved access and mobility, better health and safety, greater energy security, and cost and time savings.

“In 2010, the building sector accounted for around 32% final energy use and 8.8 GtCO2 emissions, with energy demand projected to approximately double and CO2 emissions to increase by 50–150% by mid‐century. This energy demand growth results from improvements in wealth, lifestyle change, access to modern energy services and adequate housing, and urbanization. There are significant lock‐in risks associated with the long lifespans of buildings and related infrastructure, and these are especially important in regions with high construction rates.”

“Urbanization is a global trend and is associated with increases in income, and higher urban incomes are correlated with higher consumption of energy and GHG emissions. As of 2011, more than 52% of the global population lives in urban areas. In 2006, urban areas accounted for 67–76% of energy use and 71–76% of energy‐related CO2 emissions. By 2050, the urban population is expected to increase to 5.6–7.1 billion, or 64–69% of world population.”

“The next two decades present a window of opportunity for mitigation in urban areas, as a large portion of the world’s urban areas will be developed during this period. Accounting for trends in declining population densities, and continued economic and population growth, urban land cover is projected to expand by 56–310% between 2000 and 2030.

A Review of Key Numbers

To have a chance of limiting the increase in global temperature to 2°C, we’ll have to lower emissions 40 to 70% less than 2010 by mid-century, and to near-zero by the end of this century, plus plant more trees to absorb what we’ve already emitted.

Credit: Intergovernmental Panel on Climate Change

Credit: Intergovernmental Panel on Climate Change

Annual GHG emissions grew by 1.0 giga tonne carbon dioxide equivalent per year from 2000 to 2010, compared to 0.4 from 1970 to 2000. Total GHG emissions were the highest in human history from 2000 to 2010 and reached 49 GtCO2eq/yr in 2010. Half of the CO2 emissions between 1750 and 2010 have occurred in the last 40 years.

Credit: Intergovernmental Panel on Climate Change

Credit: Intergovernmental Panel on Climate Change

As can be seen by the chart above, buildings and transportation are close to equal emitters, when electricity and heat are included, at 18% and 14%, respectively. Land use patterns and local markets are as important as green buildings when you layer on the carbon sequestration conversation. Compact development leaves more space to plant trees to absorb the carbon dioxide.

Setting out as individual agents advancing our own interests won’t do the job. Climate change is a collective action problem at the global scale, because greenhouse gases accumulate over time and mix globally, so emissions by any one of us effect all of us. We must cooperate and communicate internationally, sharing our R&D knowledge spillovers. Development, diffusion and transfer of knowledge about environmentally sound technologies is critically important.

How can city planners facilitate these knowledge spillovers and crowd sourcing? We’d like to hear how you’re tackling the problem in the comments below.

Hazel Borys

If PlaceShakers is our soapbox, our Facebook page is where we step down, grab a drink and enjoy a little conversation. Looking for a heads-up on the latest community-building news and perspective from around the web? Click through and “Like” us and we’ll keep you in the loop.


  1. Until people collectively perceive car-free communities
    as essential – 10,000 to an eco-sufficient square mile –
    all the cooperation in the world will not effect the change
    needed to offset the mass marginalizatrion of the bulk
    of world population by the wealthy. We need a
    global democratic revolution with car-free communities
    as the essential common goal.

  2. Hazel, appreciate the overview you provided in your post. Last summer, I reported from Portland, Oregon, on some of their ambitious efforts to reduce greenhouse gas emissions — including efforts to increase walkability as a way of reducing auto use and related emissions. Take a look at the following two posts: Distance, Destinations, Density at: and Wow! That’s Quite a Cut at: Perhaps some of your Portland area readers will also comment on what’s being done there.

  3. Nice summary of the IPCC! Urban density is certainly the key factor in creating the co-location of land uses that reduces motorized CO2 producing transportation, allows for co2 sequestering green space and increases cultural vitality essential to vibrant cities. But attractive and livable dense urban areas must be promoted in locations that have a level of resilience against climate change impacts. For ex. Miami is experiencing a density boom, but it is extremely vulnerable. Some of the land-use solutions will require a new and creative planning and regulatory tools – new variations on TDRs, rolling easements, temporary structures and occupancy definitions etc.. It’s time to re-think the definitions and approaches we have traditionally inherited.

  4. Again, very good and insightful work Hazel.

    You asked for anything that was missed. I don’t think there is much left out in regards to designing more infrastructure that gets us moving in the right direction for sustainable environmental change. But, I’m always focused on the bottom-line human connect for change making and what I often find left out of the conversation is something as simple as most economic and population growth ideology (and political policies) being in complete contrast to each other. Until we take in all the underlining issues and their supportive data, it will be harder to convince the political mover and shakers how to get the ecosystem from self-destructive to systemic regeneration.

    What I mean by being in political contrast is that on one side there is the economy (the business development side) which wants things that spur population growth to build their economies which leads them to investing in longevity technologies, raising the birthrate and unimpeded Growth. On the other side, (The environmentalists), there are all the issues associated with more people negatively affecting the ecosystem through having to water, feed and give them sources of income to compete in predominately capitalistic societies, which often means standing in the way of any Growth, whether its positive or not. If we want to take control of the future of earth, we have to get these two sides to acknowledge the empirical impact data that’s available and to start working together in more balanced and productive ways. We have a shared problem and both sides need to bringing their issues to the table in order to create change that supports the needs of the universal ecosystem.

  5. Thank you so much for the information.

  6. very nice blog post


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