  This chapter is dedicated to the slow dynamics of the climate system, at time
scales of one~thousand to one million years. We focus specifically on the
phenomenon of ice ages that has characterised the slow evolution of climate
over the Quaternary. Ice ages are a form of variability featuring interactions
between different large-scale components and processes in the climate system,
including ice sheet, deep-ocean and carbon cycle dynamics. This variability is
also at least partly controlled by changes in the seasonal and latitudinal
incoming solar radiation associated with the combined effects of changes in
Earth's orbit shape, precession of equinoxes, and changes in obliquity. A
number of possible mechanisms are reviewed in this chapter. We stress that the
nature of the interactions between these slow dynamics and faster modes of
variability, such as millennium and centennial modes of variability, are still
poorly understood. For example, whether the time sequence of ice ages is
robustly determined or not by the astronomical forcing is a matter of debate.
These questions need to be addressed with a range of models. We propose to use
stochastic parameterisations in the lower resolution models (focusing on
climate time scales) to account for weather and macro-weather dynamics
simulated with higher resolution models. We discuss challenges---including
statistical challenges---and possible methods associated with this programme.
