by Felix Creutzig
Can we rely on renewable energies and electric cars to win the climate race? Surely, such technologies will make great contributions, and, in fact, are absolutely necessary to achieve ambitious climate goals, such as the 2C target. Yet, they might not be sufficient.
In a comprehensive review, published in Annual Review of Environment and Resources, we investigate the role of the demand side to climate change mitigation. The review finds substantiative opportunities in particular in the food sector, and in cities. At least 20% counterfactual reductions in emissions can be achieved by reducing meat consumption, by modal shift and compacter urban form in urban transport, and in the building sector by behavioral change. The overall range is broad and uncertain, and higher contributions of the demand side are feasible.
Demand-side solutions fall into two (overlapping) classes: infrastructures and behavioural change. Infrastructures essentially form endogenous preferences and set the cost structures for consumption choices (think about the convenience of public transport or car driving in Manhattan and Houston). Behavioural change involves opportunities to change entrenched habits, partially also by modifying ‘soft’ infrastructures, e.g. by nudging.
The review also identifies key hurdles to perform assessment of demand-side solutions. Key among them is that conventional cost-benefit analysis is hard to carry out when preferences are not exogenously given. Then costs and benefits not only depend on given environmental outcomes of a specific intervention, but also on how preferences changed by the intervention. A comprehensive model of human behaviour is required (see figure above).
The demand side received only scarce attention in recent assessment reports and the reasons are not necessarily obvious. The technical difficulties certainly discourage quantitative assessments. Yet, given its likely importance, more studies should systematically tackle this challenge, notably learning from the experience in urban studies.
by Felix Creutzig
Various different scientific communities address the issue of bioenergy, climate change mitigation and sustainability. While everyone acknowledges the complexity of the issue, the emphasis in conclusions can be strikingly different. And the stakes could hardly be higher, given that the recent IPCC report points to the importance of bioenergy, especially in combination with carbon capture and storage (CCS), to reduce emissions, and even produce ‘negative emissions’: bioenergy in combination with CCS would suck CO2 out of the atmosphere and bury it underground. Hence, it becomes increasingly important to understand the differences between different strands of literature on this topic.
A recent publication, entitled, ‘Economic and ecological views on climate change mitigation with bioenergy and negative emissions‘, investigates this issue (here as pdf). The paper compares papers that emphasis biophysical limits to bioenergy production with some runs of integrated assessment models. It finds that a key difference is in the assumption space, especially assumptions on yields. If yields are increasing beyond historical rates, both food and bioenergy production can fit on existing agricultural land. If this yield increase is not realized, large-scale bioenergy production would become much less attractive. Notably, the counterfactual function of land of a CO2 sink would become quantitatively relevant, compromising the mitigation function of bioenergy.
Crucially, optimistic assumptions on yields are benchmarked in observed records in field trials. These are however only feasible with very high fertilizer and management input, and currently economically not competitive. Much will hinge not only on plant technology, but also on how management improves, also allowing for upscaling sustainable multi-purpose land use practice.
by Felix Creutzig
Most inhabitants of Hong Kong commute with the subway system, but those living in Houston, US, commute by car. Of course, it is a question of which transport mode is available. Clearly, a dense city like Hong Kong enables the construction of a subway system that is financially viable: many people use it and ridership is high. In contrast, a subway system for the Houston metropolitan area would be pointless, as each ride would be rarely frequented. This has important implications for the GHG emissions from the transport sector.
Felix Creutzig, group leader at the Mercator Research Institute on Global Commons and Climate Change in Berlin, has investigated this relationship in a paper just published in Urban Climate. “The results clarify the interaction between population density, modal share and GHG emissions from urban transport,” says Creutzig. “In a transition from a very sprawled city to a city of medium density, all GHG savings come from shorter distance traveled. However, when you cross a certain density threshold, possibly 50persons per hectare, the additional climate mitigation comes from a modal shift from car to public transit and cycling.”
The density of German cities mostly support public transit. “But as an important implication of the research results,” says Creutzig, “additional suburban development should focus on high public transit and bicycle connectivity, supported by sufficiently compact development.”
The study relies on both analytical methods from urban economics and data from world cities. As such, the paper is part of a broader research agenda that aims to utilize urban economics for questions of climate change mitigation, gauging models with real data.
The study can be downloaded on the journal website of Urban Climate.
by Felix Creutzig
The use of bioenergy for climate change mitigation remains contested. The solution part of the 5th IPCC assessment report claims that bioenergy, especially in combination with BECCS, is the single most important technology for achieving ambitious climate change mitigation goals. However, the report also reveals that this technology is highly speculative and its mitigation potential, environmental and social outcomes are a function of a considerable number of contextual variables. The results can be found in the appendix of Chapter 11 of the report, which has also been published separately as a review paper in GCB-B, labeled “Bioenergy and climate change mitigation: an assessment” by Creutzig et al. (22 authors). The paper comes up with a number of pointed conclusions agreed upon by authors from very different methodological approaches and communities.
- How much biomass for energy is technically available in the future depends on the evolution of a multitude of social, political and economic factors, e.g. land tenure and regulation, diets, trade and technology. Under ideal circumstances about 100 EJ could be harvested at low social and environmental risk; higher potentials could be possible but are increasingly associated with higher risks.
- The economic potential of BECCS is uncertain but could lie in the range of 2-10 GtCO2 per year in 2050.
- Advanced combustion biomass cookstoves reduce fuel use by more than 60% and hazardous pollutants as well as short-lived climate pollutants by up to 90%.
- Assessing land-use mitigation options should include evaluating biogeophysical impacts, such as albedo modifications, as their size may be comparable to impacts from changes to the C cycle.
- Fuels from sugarcane, perennial grasses, crop residues and waste cooking oil and many forest products have lower attributional life-cycle emissions than other fuels, depending on N2O emissions, fuel used in conversion process, forest carbon dynamics, and other site-specific factors and counterfactual dynamics (land use change emissions can still be substantial, see Figure 5).
- Land use change associated with bioenergy implementation can have a strong influence on the climate benefit. Indirect land use effects and other consequential changes are difficult to model and uncertain, but are nonetheless relevant for policy analysis.
- LUC impacts can be mitigated through: reduced land demand for food, fibre and bioenergy (e.g. diets, yields, efficient use of biomass such as utilizing waste and residues); synergies between different land use systems using adapted feedstocks (e.g. use hardy plants to cultivate degraded lands not suitable for conventional food crops); and governance systems and development models to protect ecosystems and promote sustainable land use practices where land is converted to make place for biomass production.
- Overall outcomes may depend strongly on governance of land use, increased yields, and deployment of best practices in agricultural, forestry and biomass production.
- The management of natural resources to provide needs for human society whilst recognizing environmental balance is the challenge facing society. Good governance is an essential component of a sustainable energy system.
by Felix Creutzig
Here, I report on key messages emerging from the IPCC’s report that go beyond the general messages of the Summary for Policymakers. I start with the transportation chapter, my home turf.
The key overall message is that mitigation in the transport sector is a tough challenge but that considerable opportunities are emerging, especially when we start looking outside the box, or more specifically: outside the “technology” box.
by Albert Hans Baur
Rising greenhouse gas emissions are threatening the international goal to limit dangerous global warming to maximum 2°. Although intergovernmental negotiations obviously continue to fail in effectively tackling climate change, mitigation actions become pervasive on all spatial scales. Increasingly, the focus turns on mitigation options related to urban spatial planning and behavioral change. Being responsible for 75% of global greenhouse gas emissions, cities are seen as the source for, but also as the solution to our increasingly changing climate.
In our study (Baur et al. 2013), we analyze 62 European cities and investigate the most anticipated socioeconomic drivers of urban greenhouse gas emissions on different scales (European and national). We find that population density is not, as sometimes expected, per se a strong determinant of greenhouse gas emissions. Specifically, our results show that the spatial scale of the analysis matters and that national influences modulate CO2e emissions in the analyzed urban areas.
Book review by Tiziana Susca (MCC Berlin)
In the last decades cities have been responsible for the majority of greenhouse gas emissions. In turn, the effects of climate change such as extreme natural events – for instance hurricanes – have violently plagued cities creating social and economic losses. The current ways of planning no longer guarantees safe urban environments. Since cities are the responsible of climate change they also have the potential to solve the problems in the long run both mitigating climate and decreasing their own vulnerability. In order to decrease the vulnerability of the urban environments new planning strategies should be developed to deal with the “new” climatological conditions.
Starting from these critical reflections, Rob Roggema (2012), proposes the Swarm Planning Theory to provide support to spatial designers and planners to make cities – the place in which most of the world population currently lives – climate change resilient.
By Felix Creutzig
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 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).
By Felix Creutzig
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 tonnes 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 (ERL) I, along with colleagues, investigated possible options for reducing the CO2 emissions in urban transport of the four cities mentioned above.
By Felix Creutzig
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.