Maintaining a clear line of sight through regional climate change analysis: the importance of distinguishing knowledge and data

Abstract:

Developing, or choosing, appropriate climate projections for use in a particular context is challenging. To help with this, it is useful to distinguish between two types of climate projection information. First there is scientific knowledge about the range of plausible climate change. Such knowledge can synthesise a range of relevant evidence, may convey messages in qualitative terms only, and may also have attached confidence (e.g. as in IPCC assessments).This knowledge can be used in context setting but may also be sufficient information for qualitative impact applications aimed at narrative development. Secondly, there are projection data sets tailored for use in technical risk assessments. Although these two products draw on similar source material (primarily global and regional climate model output), the information they can contain about future climate can be quite different. Often in meeting user needs, only a subset of the range of plausible future climate is considered in application-ready products. This may be due to user needs for downscaled information which comes from limited models, or their need to work with a small number of multivariate scenarios which are best provided by the outputs of single climate models. In the push to create sophisticated datasets that meet demanding technical needs, the larger perspective of representativeness can go by the wayside, and there is a risk that data users will tacitly believe their data are representative of future change when in fact they may not be. Thus a key challenge for risk assessment is for projection providers and users to work in unison to ensure that the two aspects of knowledge and data are as harmonised as possible. These concepts will be illustrated using projection products from the Australian context, including a range of new national climate projection products developed recently to support applications in natural resources management planning.