Assessing the quality of state-of-the-art regional climate information: the case of the UK Climate Projections 2018

We assess the quality of state-of-the-art regional climate information intended to support adaptation decision-making. We use the UK Climate Projections 2018 (UKCP18) as an example of such information. The probabilistic, global and regional land projections of UKCP18 exemplify some of the key methodologies that are at the forefront of providing regional climate information for decision support in adapting to a changing climate. We assess the quality of the evidence and the methodology used to support their statements about future regional climate derived from these projections along five quality dimensions: transparency, theory, diversity, completeness and adequacy for purpose. The assessment produced two major insights. First, the main issue that taints the quality of UKCP18 is the lack of transparency. The lack of transparency is particularly problematic if the information is directed towards non-expert users, who would need to develop technical skills to evaluate the quality and epistemic reliability of this information. Second, the probabilistic projections are of lower quality than the global projections. This assessment is a consequence of both lack of transparency in the probabilistic projections, and the way the method is used and justified to produce quantified uncertainty estimates about future climate. We suggest how higher quality could be achieved. This can be achieved by improving transparency of evidence and methodology and by better satisfying other dimensions through changes in elements of evidence and methodology. We conclude by recommending further avenues for testing the effectiveness of the framework and highlighting the need for further research in user perspectives on quality.