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This report for the City of Hamburg highlights that climate change adaptation is a dynamic process with many uncertainties. A core message for public sector institutions is to "bear climate adaptation in mind," especially through the integration of climate change concerns in upcoming decisions and the implementation of measures that have co-benefits today. Furthermore, adaptation activities should begin today if the costs of adaptation potentially remain constant over time or tend to rise. The case studies investigated also indicate that the evaluation of measures must take into account local conditions.

The Hamburgisches WeltWirtschaftsInstitut (HWWI) and Ecologic Institute on behalf of the Hamburg Ministry of Urban Development and Environment (Behörde für Stadtentwicklung und Umwelt, BSU), have written a report on the economic consequences of climate change and the costs of adaptation for Hamburg. The aim of the project was to gather economic results for different relevant sectors in Hamburg, to deal with selected case studies and develop recommendations.

The literature review has shown that there is a growing interest in the economic adaptation research also reflected in a significantly increasing number of publications. Both methodological advances and many new, interesting results have been developed. Some areas of activity, such as agriculture and water have been already examined relatively intensive, while others, such as human health, were considered seldom. In addition, many studies related to the national or the EU level so that support for local and regional decision-makers is limited. In this respect it is often necessary to look at adaptation measures in their regional context.

During the project four case studies on cost-benefit analyses were developed: Water Management Sector: Rising groundwater levels, Buildings Sector: Green Roofs for Hamburg, Agriculture Sector: Adapted plant species and Civil Protection Sector: The extreme rain in June 2011.

The case study results show that the used assumptions have a significant impact on the estimated costs and benefits, and that the long time horizons can lead to large bandwidths in the results. Nevertheless, important findings from the case studies could be derived. It can be showed that a green roof program could be an interesting adaptation measures with other positive side effects. Furthermore, certain impacts of climate change such as more intense extreme precipitation events require adaptation of private actors.

Other recommendations are that measures should be taken first, which show positive synergies with other policy objectives or between different measures. Further, a sufficient number of measures have already a positive effect today and thus economic benefits. In addition, today measures should be focused, with which irreversible damage can be avoided or which have a long implementation time. In the application of methods such as cost-benefit or multi-criteria analysis users and decision makers must be aware of assumptions and their impact on the results. For pragmatic reasons, it is recommended to use decision support tools and guidelines, which are either already developed or are results of current research projects.

The report (in German) Assessment of economic impacts of climate change and costs of adaptation for the City of Hamburg is available for download.

Based on the project results a poster was prepared for the event: "Hamburg, dein Regen – Fluch oder Segen", Stadtwerkstatt at 30 November 2012.