The IPCC Fifth Assessment Report (AR5) emphasises iterative risk management as its preferred approach to adaptation, but what does that mean when selecting methods for a particular assessment? Chapter 2 in the Working Group II AR5 Foundations of Decision Making introduces a wide range of factors that influence the choice and application of decision making. It focuses on making good decisions, stating that a good climate decision requires information on climate, its impacts, potential risks, and vulnerability to be integrated into an existing or proposed decision-making context. It distinguishes between simple, complicated and complex risks, showing that very different decision processes work with each. Simple methods can use straightforward, linear methods, complicated methods are more intricate and process-based, while complex methods require systems-based approaches. Elements like feedbacks, the relationship between calculated and perceived risk, institutional settings, and the behaviour of individuals and groups all need to be accounted for. While risks of all complexity are amenable to iteration in that they can be repeated, iterative and reflexive processes are part and parcel of systems-based approaches.