A comparison of hydrological climate services at different scales by users and scientists

Given the current proliferation of climate change services, how should a user judge which one is most relevant for a specific case? In this study, climate researchers and users compare continental, national and locally tailored climate change services for two case studies in Sweden with clear adaptation needs. The case studies addressed the organising committee of the large ski-racing event, Vasaloppet, for which snow availability is a concern now and in the future, and a small municipality in Sweden (Karlstad) that is prone to flooding. After meetings and online discussions with users, researchers locally tailored a service by reanalysing the data behind the national climate service. We then compared these locally tailored results with available, comparable data from the pan-European and national climate services, including the projected changes and the uncertainties provided by each service. We found that different climate change services provided different indicators, and magnitudes and directions of climate change. Differences across services are unavoidable, and limitations of climate change services are a reality of the nature of projecting an ultimately uncertain future. Therefore, we call for clearer, more explicit communication of what a climate change service provides, and detailed explanations of the limitations of climate services regarding variables, locations, scales, as well as other uncertainties. We also find that value can be added to existing climate change services by tailoring climate service outputs for a specific location or specific user requirements. Keywords: Climate services, Climate change services, Climate adaptation, Tailored climate services, Water resources, Stakeholders