The distinction of a fluctuation from a long-term change in Earth processes is a key question in the assessment of the Earth's Climate change and in general geo- risk assessment. The distinction of a fluctuation from a steady change requires knowledge on the time variability of the signal and long term observations. Due to the decadal variability of sea level, reliable sea level trends can only be obtained after about sixty years of continuous observations. Reliable strain rates of deformation require a minimum of a decade of continuous data, due to the ambient factors leading to fluctuations. The session invites contributions that demonstrate the importance of long term geophysical, geodynamic, oceanographic and climate observatories. Advances in sensors, instrumentation, data analyses, and interpretations of the data are welcome, with the aim to stimulate a multidisciplinary discussion among those dedicated to the accumulation, preservation and dissemination of data over decadal time scales or beyond. With this session, we also would like to provide an opportunity to gather for representatives from observatories in Europe and also world-wide.