To understand how processes evolve with time is crucial in many branches of Earth systems sciences. Such processes can be driven by tectonics, climate, or other causes. Processes like tectonic deformation or climate change act on very diverse spatial and temporal scales. Whereas geological processes often act on the scale of millions of years, other processes are directly observable by long-term measurements with state-of-the-art sensors. Still, years, decades, or even centuries of continuous observation, thus yielding time series with high sampling rates, are necessary to identify changes in the Earth systems, which often are quite subtle and therefore can only be assessed in quiet environments as provided by observatories. We invite contributions from various fields of Earth system sciences like geodynamics, geodesy, (paleo)climatology, just to name some. Both, case and regional studies, but also technical studies reporting on instrumental advances or modern AI-based methods to analyze time-series, are welcome.