Polar motion is an important geophysical process, and difficult to understand given the various parameters involved. But it is of key importance to our climate and climate change. Understanding and modeling also has implications on key technologies such as space geodesy and satellite navigation. Additionally, long term polar motion has close links to decadal climate change and ice cap development. It also reflects the global circulation in the hydro-atmospheric layers and the internal properties of the Earth. Therefore the topic is of primary interest for geophysics as well as climatology.