Many adaptations can be justified even if climate were not changing. Such no-regrets adaptations include improving system efficiency and flexibility and using market mechanisms to allocate scarce resources. Other decisions may require changes from what would be done if climate were not changing. Among the strategies that can be employed under these conditions are portfolio management, risk management, and adaptive management.
Portfolio management involves having a variety of responses available to meet varied outcomes. Phoenix Arizona, for example has a portfolio of options for providing adequate water supplies under a wide range of potential future drought conditions.
Risk management involves planning for low probability, high consequence outcomes. In spite of uncertainty about whether precipitation will increase or decrease, Boulder Colorado improved its ability to quickly manage more frequent or severe future droughts.
Adaptive management involves making decisions today that allow for adjustments in the future as information on climate change improves. The Thames River Barrier was built based on an assumption of a specific sea level rise scenario but is also designed to enable changes to be made should different rates of sea level rise become likely. These and other examples will be discussed in the paper.