When the set of options contains at least one long-term option, the decision may take account of future outcomes. The next relevant decision node therefore concerns whether reliable impact studies or models are available for computing impacts of adaptation options, i.e. the residual impacts.

If residual impacts cannot be computed, the task to address depends on whether the analyst is considering current or future climate risk. When considering risks from current variability and residual impacts cannot be computed, the appropriate task is to apply expected value decision frameworks (e.g. CBA, CEA, MCA) based on knowledge of the current situation. This is because in the absence of knowledge on the future climate, the most appropriate course of action is to ensure the selection of the best option in the current climate. When considering risks from future climate and residual impacts cannot be computed, the best course of action may once again be to postpone the decision and observe.

If residual impacts can be computed, scenario-based projections of future impacts (see Toolbox section on Modelling future impacts) and valuation can be carried out to calculate impacts for each option considered.