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photo:iStockphoto/clearandtransparent
Published: April 10, 2012
First published in IGBP's Global Change magazine Issue 78, March 2012

Building

our Future

Faisal Hossain is an associate professor at the Department of Civil and Environmental Engineering, Tennessee Technological University, Prescott Hall 332, 1020 Stadium Drive, Box 5015, Cookeville, TN 38505-0001, USA. E-mail: fhossain@tntech.edu

Julia Pongratz is a postdoctoral research scientist at the Department of Global Ecology, Carnegie Institution, 260 Panama Street, Stanford, CA 94305, USA. E-mail: pongratz@carnegie.stanford.edu

Features |

Human infrastructure both contributes to and is affected by global change. The engineering and climate research communities must work together to respond and adapt to such changes, say Faisal Hossain and Julia Pongratz.

As the world urbanises rapidly, our cities are becoming larger (see also The rise and rise of urban expansion); they are growing as fast as, or faster than, urban population. The modification of Earth’s surface for urban living is irreversible on human timescales and affects the local and global climate and the environment. Previous work has shown that changes in land properties such as albedo, roughness and moisture content can significantly influence climate variability at the regional scale and also affect extreme events (for example, Seneviratne et al. 2006). Several initiatives are currently fine-tuning our understanding of the impact of land-cover change on climate, including the IGBP synthesis on land-use change and climate.

While providing fodder for global-change researchers these rapid changes – coupled with the possibility of increased climate variability and economic uncertainty – are creating new challenges for the infrastructure engineering community. Urban settlements have an insatiable appetite for energy and resources, a steady supply of which needs to be assured. Take water, for example. A traditional but ubiquitous source is artificial reservoirs created by damming rivers upstream of cities. These large-scale infrastructures trap a sufficiently large amount of water from the local or regional water cycle to make up for a shortfall when demand exceeds the variable supply from nature. Although few new projects are being undertaken in the United States or Europe, large dams are being constructed and contemplated in several other nations to support agriculture as well as rapidly growing urban agglomerations. For example, the Southeast Anatolia Project in Turkey, the Three Gorges Dam in China and the proposed project to link Indian rivers.

The long-term planning of such infrastructure and the maintenance of existing infrastructure is complicated by the possibility of changing weather patterns during the coming century. But model results do not necessarily agree with each other and lack the resolution that would allow robust regional or local-scale projections. Climate models do not yet provide the kind of information needed by engineers and planners – for example, the Probable Maximum Precipitation and Probable Maximum Flood values projected into the late 21st century – that would allow testing the future functional resilience of dam infrastructure.
Despite obvious links, collaborative studies involving the engineering and climate-research communities are not common, and there is little co-design of research. There is much scope for engagement between the two communities to understand change and develop resilience.

An opportunity for engagement
Climate change will put pressure on existing infrastructure and pose new challenges for the infrastructure being contemplated by shifting mean climate and increasing the frequency and intensity of extreme climate events. In many regions the water balance will be altered by temperature and precipitation changes significantly beyond what had been anticipated when reservoirs were built. As return intervals of flooding increase, dam systems and wastewater infrastructure may exceed their capacities – for example, the Folsom Dam on the American River near Sacramento. Heat waves, such as in the summer of 2003 in Europe, which caused yield losses and ten thousands of deaths, are expected to become more frequent. Infrastructure will have to adjust to ensure sufficient resilience of energy generation and transmission, approaches to cool public facilities will need to be changed and urban green spaces will need to be increased to avert public health risks (IPCC 2011). 

Of course, infrastructure itself contributes to land-use/land-cover change. We know well the first-order changes in atmospheric temperature (for example, urban heat islands) or humidity (for example, cooler environment near reservoirs or irrigated regions) caused by infrastructure. More recently, second-order impacts on climate have been identified. For example, the downtown high-rise regions of a city can split wind and create convergence downwind leading to lifting of air and higher precipitation in certain circumstances. Increased air pollution in cities can also affect the mechanisms leading to precipitation. Incidentally, some of these effects have been also known to overwhelm city sewer systems (Reynolds et al. 2008).

Besides direct climate effects, such as changed albedo, flood control or hydropower dams can trigger a faster pace of urbanisation of the downstream valley regions, whereas irrigation dams intensify agricultural production in the vicinity of the reservoir. In a study of about 100 large dams in the US, Degu and colleagues (2011) found that dams in the Mediterranean and arid climates exerted the greatest and most detectable mesoscale impact on temperature, humidity and other storm-forming properties, whereas humid regions were least affected. This study underscores the need for a broader view of the change a dam can typically trigger during its lifespan, and has important implications for climate-change adaptation too.

In recent discussions on promoting resilience of water infrastructure, the issue of “climate change” has featured prominently as a path forward for the 21st century in some countries such as the UK (www.defra.gov.uk/environment/climate/sectors/infrastructure-companies/). This is timely, but the primary focus has so far been on adapting infrastructure in a top-down fashion to the changing extremes expected from climate-model projections. This misses the possibility of interaction of local-to-regional climate effects of large infrastructure with global climate change. For example, a warmer atmosphere implies greater capacity for holding water vapour, which might amplify the local climate impact of infrastructure. The research community studying the climate impacts of land-use/land-cover change has demonstrated clearly the impacts of local changes on the climate at various scales – the engineering community needs to pay greater heed to such research.

At the same time, the land-use/land-cover change and climate researchers are also beginning to recognise the need for better engagement with the engineering community. There is increased emphasis on understanding fundamental land-atmosphere processes and fingerprinting the direct human impact on climate. Urbanisation and other land-use change in the US and China led to an important component of the increase in mean temperatures and the decrease in diurnal temperature range observed over the last decades (e.g. Kalnay and Cai 2003). Earth-system models are consequently increasingly extended to account for effects of infrastructure on climate: for example, some General Circulation Models can use detailed information on urban structure where this is available (Oleson et al. 2010). A wide field for close collaboration may open with the new generation of General Circulation Models that allow local grid refinement in global climate simulations. Some regional climate models today already work on the level of watersheds and aim to predict local hydrological changes under given scenarios. Earth-system models will thus increasingly be able to make use of inputs about local and regional infrastructure, and may eventually allow quantification of infrastructural feedbacks on climate from the local to global scale.

Inputs from the engineering community are also needed to assess future intended and unintended consequences of human activity on climate. Scenarios of infrastructural change form part of the broader socioeconomic scenarios underlying all climate projections. As the infrastructure that might determine future climate change is largely yet to be built (Davis et al. 2011), information on infrastructural changes will be key to projections. Information on infrastructural scenarios is also needed for gauging the climatic effects of “new” or expanding land uses related to alternative energies. Large-scale wind power has been shown to have local to regional temperature effects (e.g. Keith et al. 2004). Significant changes in global mean climate seem likely only for massive deployment of wind power; the plausibility of such scenarios needs to be assessed together with the engineering community. Methods such as white roofs have been suggested as mitigation strategies and indeed found relevant for local to regional climate (Oleson et al. 2010). Strong local effects are also clearly relevant for the assessment of adaptation needs. Close collaboration between the engineering and climate communities is needed for a complete cost-benefit analysis of such proposed mitigation tools (Figure 1).

Figure 1. Collaboration for co-benefits. Projecting future climate change requires, among other things, scenarios of infrastructural change. Maintaining current and planned infrastructure and adapting to future climate change requires climate projections at local and regional scales. This interdependence can form the basis of a closer collaboration between the engineering and climate-research communities. It can help elucidate the possible local climate impacts of infrastructure.

Collaboration for co-benefits
Researchers studying land-use/land-cover change are already working closely with climate modellers to provide land-use and land-cover information as boundary conditions for climate models to be included in the fifth assessment report of the Intergovernmental Panel on Climate Change (Hibbard et al. 2010). A next step could be to involve engineers during the planning stages of research to ensure that the results can better inform design, operation and management practices. Adaptation is best served if approached locally from bottom up (e.g. Hossain et al. 2011). The engineering community should thus identify the types of information that could inform the optimal adaptation strategy for specific locations. For example, the engineering community of China might want to understand the potential impact of the land-cover change associated with large dams like the Three Gorges – and the expected increase in urban population growth – on the Asian monsoon. This requirement could then be passed on to researchers studying the impacts of land-use/land-cover change and thereby to climate modellers.

Political discussions and decisions on mitigation/adaptation options and alternative energy, for example, require a complete and comprehensive cost-benefit analysis that is currently lacking. There is growing recognition that closer collaboration between engineers and climate scientists is an important requirement for developing such analysis. Collaboration needs to be encouraged in every way possible. ❚

References
Davis S J, Peters G P and Caldeira K (2011). Proceedings of the National Academy of Sciences 108: 18554-18559.

Degu A M et al. (2011). Geophysical Research Letters, doi:10.1029/2010GL046482.

Hibbard K et al. (2010). International Journal of Climatology, doi:10.1002/joc.2150.

Hossain F et al. (2011). ASCE Journal of Hydrologic Engineering, doi:10.1061/(ASCE)HE.1943-5584.0000541.

IPCC (2011). Summary for Policymakers, in Intergovernmental Panel on Climate Change Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation, edited by Field C B et al. Cambridge University Press.

Kalnay E and Cai M (2003). Nature 423: 528-531.

Keith D et al. (2004). Proceedings of the National Academy of Sciences 101: 16115-16120.

Oleson K W, Bonan G B and Feddema J (2010). Geophysical Research Letters 37: L03701.

Reynolds S et al. (2008), in Reliable Modeling of Urban Water Systems, edited by James W. Computational Hydraulics International, Guelph, Ontario, Canada, 99-122.

Seneviratne S I et al. (2006). Nature 443: 205-209.

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