When has a glacier disappeared?

Abstract Disappearing glaciers are observed worldwide, but a reliable counting is only available for some regions. This is due to several issues, ranging from inconsistent glacier identification to different criteria applied to decide whether or not a glacier has disappeared. The public perception of a glacier being lost usually has a focus on specific, often well-known glaciers, with a related media attention. In contrast, hundreds of glaciers might disappear in other regions over the same period without any notice. When they are not widely known, this silent disappearance can also happen to scientifically valuable glaciers. For example, the loss of benchmark glaciers with decades of mass balance measurements is also a loss of important information about climate variability in remote high-mountain regions. This study gives an overview of the challenges and different criteria used to determine if a glacier has disappeared and presents recommendations for a proper counting and change assessment.