Limits to the quantification of local climate change

Wedemonstrate how the fundamental timescales of anthropogenic climate change limit the identification of societally relevant aspects of changes in precipitation.We show that it is nevertheless possible to extract, solely fromobservations, some confident quantified assessments of change at certain thresholds and locations.Maps of such changes, for a variety of hydrologically-relevant, threshold-dependentmetrics, are presented. In places in Scotland, for instance, the total precipitation on heavy rainfall days inwinter has increased bymore than 50%, but only in some locations has this been accompanied by a substantial increase in total seasonal precipitation; an important distinction forwater and landmanagement. These results are important for the presentation of scientific data by climate services, as a benchmark requirement formodels which are used to provide projections on local scales, and for process-based climate and impacts research to understand localmodulation of synoptic and global scale climate. They are a critical foundation for adaptation planning and for the scientific provision of locally relevant information about future climate.