عدم اطمینان در تاثیر تغییرات آب و هوایی بر منابع آب Uncertainty in climate change impacts on water resources

1. Introduction The common-sense meaning of the term “uncertainty” denotes lack of certainty about something, ranging from small doubts and minor imprecisions to a complete lack of definite knowledge. The broad term “uncertainty” has many various interpretations and may mean different things to different people. Uncertainty framing raised broad recognition, in relation to the “known knowns” (the things we know we know), “unknown knowns” (unknown but knowable) and “known unknowns” (expected or foreseeable conditions). The most puzzling notion is that of “unknown unknowns”, referring to things we don’t know we don’t know. They can be virtually unthinkable and may result from unforeseeable conditions that have never occurred, hence cannot be anticipated based on past experience or investigation. The term “uncertainty” is used in different contexts in natural and social and management sciences. In natural sciences, it is, primarily, an attribute of the research process, going back to the Platonic view of reality that is out there as such, however, human beings can never fully grasp it. Here, uncertainty is related to the inaccurateness of humanly devised models and research tools to describe and represent the reality (Smithson, 1989). In social sciences, the primary focus is on uncertainty impact on human decision-making (e.g. Lipshitz and Strauss, 1997). Uncertainty can be generally categorized as either epistemic or aleatory (Beven, 2016). The former is a consequence of a lack of knowledge, arising due to human ignorance and indolence. It can be reduced by gathering more data or by refining models. The latter is related to the intrinsic randomness of a phenomenon, hence there is no possibility of reducing it. In taxonomy of uncertainties proposed by Beven (2016), epistemic uncertainty is subdivided into uncertainty related to system dynamics, forcing and response data, as well as disinformation. In addition, he recognized semantic/linguistic and ontological uncertainties. The former concept refers to uncertainty about the meaning of terms and the latter is associated with different belief systems.