************************************************************************ IERS Message No. 544 December 19, 2025 ************************************************************************ EGU 2026: Earth rotation session Dear Colleagues, The EGU General Assembly 2026 will be held in Vienna and online, on 3-8 May 2026. We would like to draw your attention to the session: G3.7 "Earth Rotation: Theoretical aspects, temporal variability, physical interpretation, and prediction" (https://www.egu26.eu/session/58107). Please find below the detailed session description. We are looking forward to your contribution by submitting an abstract to our session through https://meetingorganizer.copernicus.org/EGU26/abstractsubmission/58107 The deadline to submit abstracts is 15 January 2026, 13:00 CET. More information about the EGU General Assembly 2026 can be found on the following website: https://www.egu26.eu. Best wishes, Alberto Escapa, David Salstein, Justyna Sliwinska-Bronowicz, Sigrid Boehm, Florian Seitz ------------------------------------------------------------------------ Earth Rotation: Theoretical aspects, temporal variability, physical interpretation, and prediction. Accurate modeling and prediction of Earth rotation is important for numerous applications in geodesy, astronomy and navigation. In recent years, geodetic observation systems have made significant progress in monitoring the temporal variability of the Earth's rotation, which is largely related to dynamic processes in the planet's fluid components. The increase in observation accuracy must go along with the improvement of theories and models. We welcome contributions that highlight new determinations and analyses of Earth Orientation Parameters (EOP), including combinations of different geodetic and astrometric observational techniques for deriving UT1/length-of-day variations and polar motion. We welcome discussions of EOP solutions in conjunction with a consistent determination of terrestrial and celestial frames. We are interested in the latest achievements in EOP forecasting, especially reports exploring the potential of innovative techniques, such as machine learning, in improving forecast accuracy. We invite contributions on the dynamical links between Earth rotation, geophysical fluids, and other geodetic quantities, such as the Earth gravity field or surface deformation, and of explanations for the physical excitations of Earth rotation. Besides tidal influences from outside the Earth, the principal causes for variable EOP appear to be related to angular momentum exchange from motions and mass redistribution of the fluid portions of the planet. We welcome contributions about the relationship between EOP variability and the variability in fluids due to climate effects or global change. Forecasts of these impacts are important especially for the operational determination of EOP, and the effort to improve predictions is an important topic. We are interested in the progress in the theory of Earth rotation. We seek contributions that are consistent internally with the accurate observations at the mm-level, to meet the requirements of the Global Geodetic Observing System and respond to IAG 2019 Res. 5 and IAU 2021 Res. B2, as well as those derived from the research of current IAU/IAG/IERS working groups on these topics. We also welcome contributions on the variability and excitation of the rotation of other planetary bodies. ************************************************************************ IERS Messages are edited and distributed by the IERS Central Bureau. If not stated otherwise, the IERS is only the distributor of the message and is not responsible for its content. To submit texts for distribution, please write to . To subscribe or unsubscribe, please create an IERS account or modify it: https://www.iers.org/Login/Login/EN/login_node.html or write to . Archives: http://www.iers.org/IERS/Messages ************************************************************************