This site uses cookies. By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy.
Skip to the content

IOP A community website from IOP Publishing

Recently in Sustain to gain Category

Our cities heat up. Urbanization and changes in natural environment, such as substitution of urban vegetation with impervious surfaces, formation of urban canyons and decrease in natural albedo can lead to an increase in urban temperature: the so called urban heat island (UHI) effect (Landsberg, 1981). In summer, the increase in urban temperature affects people with physical and social vulnerability (WHO, 2009) increasing the heat-related mortality (Basu and Samet, 2002). Urban adaptation strategies - such as the increase in urban albedo - can contribute to decrease urban summer temperatures and to prevent from summer weather-related mortality.

Life Cycle Assessment (LCA) is considered a useful tool for decision-makers. However, in its current use, it does not consider the contribution of the interaction between surface albedo and urban environment among the environmental burdens. The variation in albedo is able to affect global climate (i.e., radiative forcing), local climate (i.e., UHI adaptation) and micro-scale (i.e., life cycle inventory of the roofs).

A new study by Tiziana Susca (2012a) proposes an enhancement of the current use of LCA considering a multiscale approach. It includes the evaluation of the potential change in impact on global, meso and micro-scale due to the increase in urban albedo. In particular, the author developed a methodology to include in LCA the effect that the decrease in temperature - due to the citywide albedo - has on human health. The theoretical framework was applied to the case study of the New York City´s rooftops. New York City is plagued by a UHI of about 2°C (Susca et al., 2011) and it is the most populous city in the U.S. This means that the decrease in summer temperature can positively affect a large number of people.

The main aim of the research was to evaluate the contribution of surface albedo in affecting the impact on global climate and on human health. A functional unit of one square meter of white roof was evaluated in the time-horizons of 50 and 100 years. An increase in the urban-wide rooftop albedo from 0.32 to 0.9 - the maximum value that a surface albedo can reach - was proposed. Through the use of an existing climatological model developed by Oleson and colleagues (2010) the mitigation in urban summer temperature in the City was evaluated. The effect on human health was evaluated through the use of both statistical (i.e., life expectancy for different classes of age) and epidemiological data (i.e., risk ratio related to the number of deaths for natural cause in New York City). The mitigation in summer mean temperatures was translated in Disability Adjusted Life Years, the metric that LCA uses for the evaluation of the impact of products, services and goods on human health. The impact on global climate related to the variation in rooftop albedo was calculated through the use of a time-dependent climatological model developed by the same author (Susca, 2012b).

The results of the study show that surface albedo decreases the impact on climate change of one square meter of roof by approximately 84% and on human health of about 3% in a time-frame of 50 years. Besides, in a time-horizon of 100 years the estimation of the effect of surface albedo respectively on global climate and on human health shows a decrease in the impact of 70% and 6%.

The study shows that surface albedo is an important optical characteristic that should be considered in LCA application. Furthermore, the study highlights the importance of the use of a multi-scale approach in LCA that considers the multiple interactions with the urban environment.   


Basu, R. and J. M. Samet. 2002. Relation between elevated ambient temperature and mortality: A review of then epidemiologic evidence. Epidemiologic Reviews 24: 190-202

Landsberg, H. E. 1981. The urban climate. International Research Series, Vol. 28. New York, NY, USA: Academic Press

Oleson, K. W., G. B. Bonan, and J. Feddema. 2010. Effects of white roofs on urban temperature in a global climate model. Geophysical Research Letters 37. doi:10.1029/2009GL042194

Susca, T. 2012a. Multiscale Approach to Life Cycle Assessment Evaluation of the Effect of an Increase in New York City´s Rooftop Albedo on Human Health, Journal of Industrial Ecology, 16 (6), 951-962

Susca, T. 2012b. Enhancement of life cycle assessment methodology to include the effect of surface albedo on climate change: Comparing black and white roofs. Environmental Pollution 163: 48-54

Susca, T., S. R. Gaffin, and G. R. Dell'Osso. 2011. Positive effects of vegetation: Urban heat island and green roofs. Environmental Pollution 159 (8-9): 2119-2126

WHO (World Health Organization). 2009. Protecting health from climate change. Connecting science, policy and people. Accessed May 2011 

Citizens of Europe enjoy high accessibility to energy efficient modes of transportation, such as public transit, and often can cycle safely in cities. Still, CO2 emissions in urban transport measure about two tons per capita each year even in well-designed cities such as Barcelona, Freiburg, Malmö, and Sofia. For ambitious mitigation these numbers need to be cut considerably. But automobile-centered structure of the periphery makes decarbonizing a daunting task. In a new study in Environmental Research Letters Creutzig and colleagues investigated possible options for reducing the CO2 emissions in urban transport of the four cities mentioned above.

A first look suggests that European fuel efficiency regulation already contribute their relevant bit: In BAU scenarios with relatively low additional demand (demography; trend in transport policies) more efficient cars due to suggested 2020 regulation will lower GHG emissions about 40% until 2040. But the ERL-study focused most on urban transport policies. These were clustered into three classes: "Pull" policies that attracted citizens into more efficient modes, such as tram-ways, bus rapid transit, and bicycles; "Push" measures that made the use of CO2 and energy intensive modes less attractive, e.g. reduced and more expensive parking space; and "Land-use" policies that enable the use of public transit and cycling by increasing accessibility on short-to-medium distances.

The study reveals that the combination of pull, push and land-use measures reduces CO2 emissions by an additional 40-70%, measured from the technology BAU scenario, and brings per capita emissions down to around 0.6t annually. The pull scenario brings only a small contribution, as many commuters prefer to stay in their cars. However, if push measures are added on the pull measures, a significant modal shift is expected: Car driving becomes more expensive, and additional space for walking, cycling and busses makes those modes even more attractive. Land-use measures such as densification and the prohibition of big boxes outside the city proper contributes a few more percentages to decarbonizing. This is particularly so in Malmö, a city that is in now in commuter distance to Copenhagen and is expected to grow considerably in population size. New medium-dense and transit-oriented development would make a huge difference here.

Crucially, the study demonstrates huge benefits in public health, and transport efficiency, accompanying such a decarbonizing strategy. Fuel spending would be reduced by billions of Euros annually, keeping more of spent income within city regions. Congestion would be reduced, enabling faster traffic for taxis and a down-scaled car fleet. At the same time, more cycling and walking would decrease coronary and other diseases, and cleaner air would improve well-being and reduce asthma incidents. 

The paper by Creutzig and colleagues highlights that decarbonization might be beneficial on a societal level, changing the debate of climate change mitigation from costs to benefits. It would be interesting to integrate such perspectives into conventional cost-focused studies of climate change mitigation.

Last week's hurricane, humanized as Sandy, crashed the East Coast, killed more than 100 people and injured many more. Lower Manhattan got flooded, and New Jersey still looks like a disaster zone that we were used to see from the distant places such as the Caribbean islands. Our infrastructures are neither resilient to climate change, nor helpful in reducing our greenhouse gas emissions.

There is no doubt that human-made climate change systemically caused this extremely powerful and unusual hurricane. Atlantic water temperature considerably exceeded its long-term average and the melting of Arctic ice produced a high-pressure system pushing the Hurricane to the most densely populated area of North America. The scary news is that hurricane Sandy won't be the exception. Climate change is happening and our action will determine whether such storms hit our coasts annually or only every other decade.

Climate change has for too long been regarded as a high-level abstract entity to be dealt with high-level policy instruments such as cap-and-trade. But climate change impacts real people, and it is time to bring action to those affected. No doubt, few things would be more effective than a tax or price on CO2 emissions (and this could easily be done in a revenue neutral way, for example reducing payroll taxes in return). But such a price instruments works on the margin, it ignores the stocks our society operates on, its infrastructure. We also need to make our infrastructures climateproof.

The hurricane exposed the weaknesses of existing infrastructures. Old above-ground transmissions lines went down, still leaving the poorer outskirts of New York, the commuter towns of New Jersey in a desperate situation. The backbone of New York transit was hit when the subway tunnels got flooded. As citizens reverted to cars, the city became clogged in congestion; gasoline shortages still impact many and endanger the most vulnerable. The hurricane effectively revealed inequality in infrastructure access - mirroring inequalities in income and wealth.

Fortunately, reshaping and reconfiguration of our infrastructures can reduce our carbon footprint, can increase our resilience to climate change, and improve the quality of everyone's life.

Let us take the example of urban transport. Here is a bold three-point transformation plan for New York:

First, make auto-mobility public. More than 95% of the time, cars are parking idly. That wastes much precious space in dense cities. Offering public cars, which can be accessed with smartphones and electronic IDs, saves parking space, and time for cruising. Significant resources can be saved on unnecessary car ownership. Cars would cease to be the default mobility option in cities, effectively reducing CO2 emissions. A car got crashed in an accident or in a hurricane? Public cars would provide collective insurance and guarantee accessibility. In rural or ex-urban areas, private cars would remain the predominant solution.

Second, improve infrastructure for cyclists. The Copenhagen example shows that expanding the bicycle network, and making it safe, can attract a huge number of users with modal shares exceeding 40%. Cycling is healthy and can make commuting a quality experience. E-bikes would enable routine 10 miles commutes. While cyclists also cause accidents, those accidents are less fatal, and cyclists cause neither air pollution nor noise nuisance. Cities become more livable. And cyclists are disaster resilient, as they neither need electricity nor gasoline.

Third, mass public transit should be put back into streets. Subways are incredibly expensive and remove citizens from daylight. Bus rapid transit and tram systems can be affordable even to tight municipal budgets. With pre-boarding ticketing and way of right, on-street public transit can speed up and carry high numbers of passengers. Bus rapid transit systems would also be more resilient to flooding, backing up more vulnerable subway tunnels.

Such a transformation is challenging, and politicians will struggle to address the concerns of many different constituencies. The barrier to this transformation is hardly a monetary one, but a question of leadership. But there are signs of hope that Bloomberg and other mayors can push us forward where federal government fails.

Governments seek to mitigate climate change and make their countries energy independent. Biofuels seemed to achieve both: sequestering the carbon they emit, biofuels were considered carbon neutral; they also rely on intra-regional resources, notable land, and reduce oil imports.

But studiy after studiy points to unforeseen dangers. The current aggressive deployment of biofuels compromise food security; and perversely, biofuel production contributes to climate change by releasing carbon formerly stored in soil and forests (indirect land use change, ILUC).

The European Commission finally awakes to this challenge. The Guardian reports that the Commission aims to reduce the mandated quota of biofuels from 10% to 5% in 2020, a level that is already achieved now. Equally important, indirect land-use change will be part of the metric.

If policy makers reduce quotas, forests, peat lands, and food production gain maneuvering space. The EU would directly alleviate land-based ecosystem and communities from potentially harmful pressure. But what are the implications of the ILUC factor?

Chris Malins published his research on precisely this question in Global Change Biology last month. Malins is confident that "introducing iLUC factors will make the policies more effective and will greatly reduce the risks of doing more harm than good". In his model (given a required 50% thresholds on carbon savings), "there is a 94% chance that introducing iLUC factors would improve the carbon saving per unit of energy achieved by EU biofuels policy by at least 20 percentage points, with an expected benefit of 49 percentage points, i.e. iLUC factors would be expected to be a very effective policy intervention".

The implications for the European biodiesel industry are devastating; European biodiesel production seems currently unable to meet the requirements, biodiesel would be pushed out of business. Understandably, the biodiesel lobby is outraged.

But if a policy designed to mitigate climate change, instead aggravates climate change, it remains the right decision to change course. The ILUC policy in particular is suitable to navigate the climate-change Scylla of fossil-fuel dependency and the climate-change Charybdis of land-based emissions: the ILUC factors put pressure on markets to come up with low-emitting second-generation biofuels (long announced but hardly been seen so far). 

Is this the end of the line, or just a foot in the door? I would argue that a revised EU regulation of ILUC is just the entry point for something much bigger, allowing science and policies to grow to meet the tremendous challenges we are facing. The main issue is the interconnectedness of energy, food and climate dynamics and policies.

Scientifically, what is the counter-factual fossil fuel used for bio-refineries? Which combination of food, fuel, and forest policies leads to what kind of land use (emission) outcome? I am certainly not the only one to suggest that the true relevance of biofuel policies only reveals itself in the context of world agricultural politics, food demand, and forest protection efforts.

Politically, why should biofuels be carefully discriminated against their global warming potential (what I fully support), when food production is not? How does the effectiveness of ILUC regulation depend on the proper and stringent enforcement and continuation of carbon prices for fossil fuel, and caps?

The Scylla and Charybdis of biofuel policies is only one adventurous incidence of a much larger Odyssey.


Further reading:

F. Creutzig, A. Popp, R. Plevin, G. Luderer, J. Minx, O. Edenhofer (2012) 

Reconciling top-down and bottom-up modeling on future bioenergy deployment.

Nature Climate Change 2: 320-327 

In a recent blog, I discussed an article by Echenique et al. (2012). The paper points out that urban form policies have a rather moderate impact as population growth and land consumption trends dominate the overall dynamics. In my blog I suggested that EU fuel efficiency regulation for new cars should demonstrate higher impacts on reducing GHG emissions. Anil Namdeo from the author team responds with the following reply:

"The Trend trajectories are largely driven by the high rate of growth in the region (London and South East): the number of dwellings increase by 30% over the Trend, a product of a 19.1% growth in population and a reduction in household size. Road traffic grows from 220 billion vehicle kms in 1997, to 338 billion vehicle kms in 2031, an increase of some 1.57% per annum. This growth eventually counteracts the gains in noxious emission (NOX, PM10, CO, VOC) reduction won via clean technology. Although newer vehicles will be more fuel efficient, CO2 emissions continue to rise because of the growth in vehicle travel and the increase in congestion and because we have not assumed carbon neutrality for new dwellings as these have yet to be achieved in mass market building. The lower speeds associated with congestion create additional emissions due to frequent stop-start operation of vehicles."

From my point of view, this discussion demonstrates that urban form measures are insufficient on their own to achieve ambitious GHG abatement and other environmental targets. Instead, I argue that a combination of land use, push and pull policies can achieve synergies resulting into a relatively low-carbon urban transport world.

Does Urban Form Really Matter? This is the subtitle of a paper by Echenique et al., just published in the Journal of the American Planning Association.

The paper scrutinizes the claim that compaction makes cities more sustainable. Starting point is the finding of the US Commission of Integrated Transport (2009) that compaction has a modest effect in reducing vehicle travel. Echenique et al. posit that the social and economic costs needs to be treated comprehensively. Using modifications of the advanced transport-land-use model software MEPLAN, the authors model the impact of three different land-use developments in three English regions/cities, identifying 26 sustainability indices. The three developments are labeled dispersal, planned expansion, and compaction. Compaction reduces CO2-emissions from buildings and transport only between 1-5% compared with the dispersal scenario running from 1997 to 2031. Moreover, the differences in land-use due to spatial configurations are small compared to the impact of socio-economic change and population growth.

A little surprising is the relatively high increase in transport energy use of 10-38% from 1997 to 2031 in the baseline scenario (the other scenarios are only marginally different). With EU regulation, CO2-intensity of new cars will be reduced in average from >180gCO2/km in 2005 to 130gCO2/km in 2015 and (planned) 95gCO2/km in 2020. This massive reduction is mostly achieved by energy efficiency measures and is sufficient to reduce transport energy use even with increasing population and growth (assuming a car turnover time of 15 years). It would be interesting to see the underlying assumptions in the scenarios of this paper. (The background report at speaks about "slightly more fuel efficient vehicles" without specifying details). However, irrespective of technological advances in vehicle fleet, the conclusions on compaction relative to the other scenarios remain valid.

Most interesting then is the net economic benefit. Also here, trend dominates the overall results: In baseline, economic costs of land use are high, as land prices and congestion increases, reducing economic competitiveness and costs for residents. Spatial developments make hardly a dent in this calculation and with different sign depending on the circumstances (compaction is suggested to be economically beneficial for the Cambridge region but economically disadvantageous for the other English areas studied). This aspect deserves more exploration. One can include various aspects into such cost calculation. For examples, one could include the time and convenience savings in non-motorized transport. Or one could develop a scenario where the increased monopoly land rents are taxed and other more economically harmful taxes on labor and capital are decreased. Such assumption would considerably change the results.

This consideration aside, the paper powerfully demonstrates that urban form policies have rather moderate and context-depending effects for reducing CO2-emissions. Compaction is no silver bullet. In turn, research focus should increasingly focus on sets of integrated policies, combining urban planning, transport demand management and infrastructure investment, identifying possible synergies and opportunities. 

Walking and cycling dominate urban transport in Asia and Africa. This statement is worth repeating. Walking and cycling dominate urban transport in Asia and Africa. It is one of the key statements in the book "Urban Transport in the Developing World", subtitled "A Handbook for Policy and Practice", edited by Harry Dimitriou and Ralph Gakenheimer. But it is much more than a handbook. It is the most comprehensive overview on the topic. With more than 600 pages, take your time reading it. While there is some redundancy, reading this book carefully will provide you with a superb, encompassing understanding of urban transport in the developing world.

Here is the book's story. 60% of the world's population live in Asia, and Asia is the epicenter of the global urbanization wave. Asia is also the focal point of incredible motorization with China alone being projected to have in 2050 nearly as many cars, as the world has currently on its roads, in totol: 700 million cars. An Asian city also gives its name to one of the key concepts I extracted from the book: the Bangkok syndrome. Similar to their OECD counterparts, Asian and African cities start with dense, walkable city cores. At the beginning of the last century, OECD cities invested in the then upcoming rail-based transport infrastructure, shaping cities profoundly. With the relatively slow but profound rise of automobility, American cities developed into low-density automobile cities, while European cities kept their inner cities served with public transit. Asian and African cities seem to be mostly on a different trajectory: They skip the stage of public transport infrastructures and move directly into individualized motorized mobility. This is too some degree quite surprising: Relative to their GDP, cities of the developing world invest much more into highways, citizens proportionally much more into personal transport than their OECD counterparts do and have done (see e.g. Jeffrey Kenworthy's contribution). Inversely, these developing cities have high population density and are unsuitable for car transport. As a result, especially Asian cities develop into 'motorcycle' cities (Barter, 2000): motorized two-wheelers are best adapt to navigate the traffic disasters, but are subject to high accident rates and still face congestion.

Distribution and accessibility is another, related theme that develops continously across chapters. As the introductary statement indicates, paraphrased from Setty Pendakur's chapter, non-motorized transport is the starting point of analysis, for transport efficiency and transport equity matters alike. Urban transport planning is often technocratically framed as 'apolitical intervention' (Eduardo Vasconcellos), where in fact it is top income segment who by driving their cars consume 10 times more space than the urban poor, consume a largest part of transport energy, and are responsible for most of street-level air pollution. It is then quite clear that a suitable normative objective for urban transport is reasonable accessibility for all, possibly emphasizing the urban poor (the concept itself actually may need to be qualified, see Xavier Godard's chapter). Accesssibility itself is a highly interesting concept: Some cities, such as Dakar, seem to have high accessibililty - walkability - for the poorest quantile. In contrast, in cities like Buenos Aires the lowest income quintile pays proportionally to income much more than the richest quantile. Poverty may also directly reduce social contact by rendering visits to family or friends infeasible.

In line of the this comprehensive analysis, it then follows naturally to require comprehensive assessments of urban transport projects and plans, relying on strategic environmental assessments (Michael Replogle), inclusive equity evaluation (Eduardo Vasconcellos), and context-specific economic appraisal (Walter Hook). The key conundrum, however, is then in the meta-level of institions (Elliott Sclar and Julie Touber). In the dense urban environment of Asian and many African cities, the traffic disaster of the Bangkok syndrome can only be tackled with efficient public transport. But public transport can be regarded as a quasi-public good, and will not emerge from demand-side focussed market outcomes. Hence institutional capacity, a governance framework of promoting public goods and better public transport and non-motorized transport system need to coevolve simultenously. Transport planning alone is not enough.

Planet Under Pressure integrates more than 3000 people of diverse research communities into a four-day conference in London these days. What this conference makes really great is that people from very different disciplines talk to each other and try to get the social and environmental issues together from various angles: demographics, climate change mitigation and adaptation, migration, infrastructures, cities, subsistence farming, and so on.

You can follow the plenary discussion online!

In the demographics session today, the report Migration and Global Environmental Change was presented.

One key insight is that migration, in terms of percentage of total population, remains largely unchanged. Migration is driven by multiple causes, and environmental threats can be dominant in specific cases. Crucially, the report understands migration as adaptation of individuals and households – it does not need to be interpreted as something that needs to be avoided. In fact, more worrisome than migration can be the absence of migration: the poorest part of populations in many cases lacks the (financial) capacity to move around.

Another result of the report is that migration often leads to higher exposure of environmental hazards (e.g. when urbanization increasingly results in migrants occupying land under high flooding risk).

The mismatch between insight on the need for climate change mitigation and implemented policies is amazing. Seemingly, this is a particularly hard global common good problem. So why not push much harder for pure win strategies. Pure win strategies often lack the intelectual appeal of a global cap and trade and, for being so nitty-gritty, put less glory on policy makers. But they can be valuable entry points for global cooperations. Here is one example.

Diesel fuel reserves tax benefits in most Asian countries, and is favored in vehicle regulation. At the same time, pollution control is weak at best. At a result, vehicles powered by diesel emit tons of black carbon in addition to CO2. Black carbon is the third most gaseous contributor of climate change and has most of its climate impact on short time scales (more like 20 years), whereas CO2 remains in the atmosphere for more than 100 years in average. Black carbon and other diesel exhaust also pollutes the air breathed by billions of Asians, causing asthma and lung cancer.

Here is the strategy as developed by Minjares and Rutherford (both from ICCT, San Francisco) in the upcoming book "Low Carbon Transport in Asia" by Zusman, Srinivasan and Dhakal:

  •  Make particle filter in diesel vehicles mandatory. This can dramatically improve air condition for Asian city dwellers in the upcoming decades. Even more, this single measure can reduce GHG emissions by 14% on a GWP20 basis and by 4% on a GWP100 basis. Not the killer app, but considering the huge health benefits, this is a straight forward measure.
  •  Switch to carbon-neutral fuel emission standards (i.e. corporate average, not weight-based, and I would insist, also not size-based). Asian countries can rely here, as well as for pollution control, on the well-established technological advance from OECD countries. No need for R&D investments here.
  •  Finally, tax benefits for diesel vehicles can be scrapped, and taxation can follow the GHG content of fuels only.

These measures require some institutional capacities, but not much financial resources from governments. That is probably where industrial countries or the Asian Development Bank can come in with support. But Asian countries profit most, besides climate mitigation, improving public health conditions drastically, especially for the poor, and raising tax revenues simultaneously.  

Enhanced by Zemanta

Developing Asia is at a crossroads, transport-wise. And integrating co-benefits in transport decision-makes the difference. That in a nut-shell is the message of the book Low Carbon Transport in Asia - Strategies for optimizing co-benefits by Zusman, Srinivasan and Dhakal, just getting published at Earthscan.

The book builds on established approaches to quantify co-benefits of sustainable transport benefits. According to perspective, climate change mitigation is a co-benefit of air pollution combat or transport management or, the other way around: a better air quality is the co-benefit of ambitious climate protection. With close to half of the world population living in mostly densely populated Asia, the exposure of transport impact is particularly relevant on this continent - a co-benefit approach will deliver most in Asia. The book, an organized collection of articles around this topic summarizes conceptualization efforts and developes case studies on realizing transport co-benefits. Crucially, the book manages to transcend pure quantification efforts and analyzes barriers to co-benefit strategies and corresponding solution strategies. Zusman et al. identify two main avenues: A) clean and affordable technologies for motorized vehicles that can have huge impact on improving the health of billions of Asians while also substantially reducing non-CO2 greenhouse gas emissions; and B) transport demand management strategies that are even more comprehensive, also addressing congestion, safety, and accessibility issues, but are also more ambitious.

While there is some overlap across chapters, all a well edited and are a very good read. The true value of this book, however, is its success in bringing the transport co-benefit literature together, providing an excellent overview for scientists and policymakers. 

Disclosure: I contributed to this book project.