AbstractThe core of climate services is to provide high quality climate-related information and data that are beneficial for the users. Between the provision of data and the application of climate services, a chain of providers and subsequent users exists. It is an ongoing challenge for providers to conclusively define what users perceive as beneficial regarding the quality of climate model output. This study aims (1) to understand the needs of users with regard to the quality of climate data and information, and (2) to enable providers to assess the quality of climate data input and derived products. From a large-scale survey, we distilled three main user groups: (i) Donna data (data user/product provider), (ii) Pete product (product user/product provider) and (iii) Nick non (potential-user). The survey results show that all three user groups struggle—amongst other things—with identifying reliable climate model output, that is relevant to their needs. They also desire guidance on how to evaluate the quality of climate model data to determine the suitability of the selected dataset for their purpose. Addressing this central need is breaking new ground. The evaluation of quality in the field of climate services in terms of climate model output is of high relevance to both climate model data users and providers of tailored climate information and not restricted to scientific standards and technical quality. We present a customized and tested tool (“QUACK”) as one of the first hands-on, scientifically-based and at the same time user-oriented guidelines on how to assure data quality and to self-evaluate the processing of the data.