<p>Glacial-interglacial cycles are global climatic changes which have characterised the last 3 million years. The eight latest<br>glacial-interglacial cycles represent changes in sea level over 100 m, and their average duration was around 100 000 years. There is a<br>long tradition of modelling glacial-interglacial cycles with low-order dynamical systems. In one view, the cyclic phenomenon is caused by<br>non-linear interactions between components of the climate system: The dynamical system model which represents Earth dynamics has a limit cycle. In an another view, the variations in ice volume and ice sheet extent are caused by changes in Earth's orbit, possibly amplified by feedbacks.<br>This response and internal feedbacks need to be non-linear to explain the asymmetric character of glacial-interglacial cycles and their duration. A third view sees glacial-interglacial cycles as a limit cycle synchronised on the orbital forcing.</p><p>The purpose of the present contribution is to pay specific attention to the effects of stochastic forcing. Indeed, the trajectories<br>obtained in presence of noise are not necessarily noised-up versions of the deterministic trajectories. They may follow pathways which<br>have no analogue in the deterministic version of the model. &#160;Our purpose is to<br>demonstrate the mechanisms by which stochastic excitation may generate such large-scale oscillations and induce intermittency. To this end, we<br>consider a series of models previously introduced in the literature, starting by autonomous models with two variables, and then three<br>variables. The properties of stochastic trajectories are understood by reference to the bifurcation diagram, the vector field, and a<br>method called stochastic sensitivity analysis. &#160;We then introduce models accounting for the orbital forcing, and distinguish forced and<br>synchronised ice-age scenarios, and show again how noise may generate trajectories which have no immediate analogue in the determinstic model.&#160;</p>