What urban decision-makers need to know about climate change

The process of creating ARC3 began with a scoping activity to solicit the key questions that urban policy makers need answered and to survey current topics in urban climate change research (UCCRN, 2008). Five questions were developed and sent to mayors, their staffs, and/or UCCRN research partners in approximately 45 C40 cities around the world and decision-makers from 15 cities (from both developing and developed countries) responded. Informal discussions about ARC3 also took place with city leaders at the C40 Large Cities Climate Summits held in New York in 2007 and in Seoul in 2009.

The survey questions focused on the climate-related challenges that cities face and information needs for adaptation and mitigation policies. The survey questions included:

What climate-related challenges does your city face?

Where are adaptation policies and actions most urgently needed?

In what fields do you see potential for strong mitigation efforts in your city?

What policy mechanisms is your city potentially or actually implementing?

What other special issues would you like the ARC3 to address?

The main themes that emerged as a result of the city-stakeholder responses and that have been incorporated into the content of the ARC3 are vulnerability, science-policy links, urbanization and land-use issues, and equity and environmental justice. These themes were then incorporated into the sector topic templates. The volume thus responds to expressed stakeholder needs as well as it draws from and provides broader perspectives on urban mitigation and adaptation to climate change.


Regarding vulnerability, the stakeholder concerns deal with the impacts on their inhabitants of the predicted increase in hotter days, likelihood of more intense rain events at potentially more frequent intervals, flooding that will likely result from these rain events, and sea level rise and storm surge. One inland city’s authorities pointed out that they also need to be concerned with sea level rise since they are a likely destination of people seeking refuge from higher seas and the accompanying damages from coastal flooding.

Science-policy linkages

The second theme that emerged from the stakeholder survey is the challenge of linking science and policy. City decision-makers are unsure how much mitigation and adaptation they should undertake, when, and at what cost. Methods for risk assessment are needed since there is a large amount of uncertainty in climate change science. Related questions brought forward by stakeholders include: Who should be assessing the risks a city faces, how can risks be assessed effectively and efficiently, and how often should risks be reassessed?


The third theme is the challenge of dealing with ongoing urbanization in conjunction with the climate-related challenges that cities face. A major concern is the potential for increasing flooding to disrupt urban development along coasts and rivers. For developing cities, a key issue is how to plan for new infrastructure, taking climate change adaptation and mitigation into account. For developed cities, the challenge is often related to retrofitting existing infrastructure to make it more energy efficient and climate change resilient, but siting and protecting new developments along coasts and rivers are challenges in developed cities as well. Another question raised by city stakeholders relates to the urban heat island effect: What will be the impacts on their city’s population and the surrounding areas of the combined effects of the urban heat island and climate change?

Equity and environmental justice

The fourth theme to emerge from the urban stakeholder responses relates to equity and environmental justice. Many of the same populations are vulnerable to the effects of climate change regardless of whether they find themselves in a developed or developing city. These populations tend to be the elderly, the very young, and the poor in cities everywhere.

Climate risks, adaptation and mitigation, and governance

Some specific climate change topics that respondents wanted ARC3 to address include urban climate risks, adaptation and mitigation and their interactions, and strategies for effective policy development.

City leaders wanted to understand key climate processes that pertain specifically to urban areas, such as how urban areas are simulated in climate models and the critical interactive processes related to the urban heat island effect, climate change, and their effects on urban populations.

Urban policymakers are particularly interested in knowing how to decide when and how much to adapt to climate change. They want to ensure that adaptation is flexible enough to deal with the uncertainties in climate projections. Further, they asked for help in identifying the point at which adaptation needs to go beyond simply making incremental improvements and in undertaking explicit revision of existing standards and practices.

In regard to mitigation, city decision-makers require information on determining the role of renewable energy in urban areas and its relation to emerging technologies at various scales. They also see the need to link climate change to the broader energy agenda – including access to energy, poverty and equity issues, fuel choice, and energy network infrastructure – rather than considering it in isolation.

Urban policymakers are well aware that adaptation and mitigation responses are interactive, and that their interactions can be positive or negative. The goal is to enhance the synergies between mitigation and adaptation, while minimizing the constraints. Key policy areas for explicitly addressing these challenges are: retrofitting existing urban residential development and infrastructure to reduce greenhouse gas emissions as well as heat stress of residents; and devising strategies for seaports and airports, since they are both vulnerable to climate change and central to reductions of greenhouse gas emissions.

At the governance level, a key issue that the ARC3 addresses is the need to delineate the role of the city authority in regard to climate change compared to regional, national, and international bodies. This is germane to another need expressed by city stakeholders, which is determining climate change risks and levels of acceptability.

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