Lessons in climate service development from Klimaatlas, the Danish National Climate Atlas

Responding to the challenges of a changing climate requires information that is relevant and actionable at the local scale where adaptation actions take place. Here we describe the development of Klimaatlas, the Danish National Climate Atlas, a tool to provide information to ministries, regional authorities, businesses and citizens about climate change in Denmark.  We focus in particular on the key decisions that needed to be made during development and the lessons learnt from doing so that are relevant to the development of similar tools in other jurisdictions. We describe the user groups that we involved in the development of the atlas, how their interactions shaped the final product, and the ongoing role of the user in the project. Communication and dissemination of results was approached on three different levels simultaneously, and we describe this approach, and its benefits, in detail. We detail some of the major technical challenges faced, particularly around the choice of bias-correction methods, and how these issues were overcome. The approach to quantifying and communicating uncertainty, and its importance, also receives particular attention. We assess the impact of Klimaatlas, and the challenges around quantifying its usefulness, together with the results of a recent user survey identifying the strengths and weaknesses. We also place Klimaatlas in the context of other comparable products, and particularly the recently developed IPCC Interactive Atlas. Finally, we discuss issues around future maintenance and possible expansions of Klimaatlas, including the use of convection permitting simulations, incorporation of compound events, updates between IPCC cycles and extensions to new sectors.