The IPCC's Fifth Assessment Report acknowledged the lack of standard metrics to measure and monitor success in urban adaptation and suggested a list of indicators that could be developed, while also taking note of the localised nature of adaptation . However, predominant approaches are typically not conducted at the appropriate scale to inform adaptation decision-making . While some scholars advocate the use of a unifying indicator of social vulnerability , others propose to develop flexible sets of comparable indicators that can be adjusted to different contexts . Risk-based approaches are seen as an alternative in a context where the monitoring of decision-relevant variables in urban climate adaptation planning is essential to link climatic risk assessment and action . Because of the need to define normative frameworks for risk evaluation, what is acceptable, for what purpose and for how long , these approaches may offer an opportunity for the generation of a shared understanding on goals and limitations of adaptation . However, risk-based indicators may also create a bias toward quantifiable variables that tend to be based on climatic modelling outputs, engineering or financial assessments. Based on this and various examples of urban development projects, Hallegatte and Engle  claim it is important to consider output-based indicators and process-based indicators that talk about government, voice and empowerment. Overall, dozens of indicator-based approaches to assess climate adaptation have been proposed across the scientific and policy literature, especially in the broader framework of  resilience assessment tools , and in different sectors, for example the climate benefits of NBS . Although these efforts may help to mainstream the evaluation of adaptation in current city evaluation initiatives, the development of comprehensive monitoring and evaluation systems is lacking.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report