See attached file for the review

The authors use a Saltzman-style 3-equation in 3-unknown model of the ice ages. They explore the response to pure obliquity, pure precession, and combined Milankovitch forcing, and examine the dependence on initial conditions. There is no question that the subject is interesting and important. The authors use a relatively simple model, which again is very appropriate in this context. It seems, however, that the paper largely repeats previously published analyses, which the authors do not discuss. I recommend a major revision that will allow the authors to search and examine the related literature, discuss it, and reformulate their analysis and discussion in a way that focuses on some novel elements to be identified.

The authors may want to take a look at Tziperman et al. 2006, "Consequences of pacing the Pleistocene 100 kyr ice ages by nonlinear phase locking to Milankovitch forcing", as well as papers that are cited and cite this paper. This could be a useful entry to the idea that glacial cycles are phase locked to Milankovitch forcing. Figures 1 and 2 in the current paper, and possibly additional ones, seem to repeat analysis in that paper and in related papers that have been written by multiple authors. Phase locking to Milankovitch implies that different initial conditions converge to the same ice volume trajectory. This seems directly relevant to the goals of this paper, yet this draft does not mention this concept.

The initial couple of paragraphs where simple models are advocated seem unnecessary in this research field where simple models have been used for many decades now, including in multiple interesting papers by the lead author.

I am not convinced the analysis of the linear equation (1) and its solution (2) adds a meaningful message. "A model should be as simple as possible, but not simpler". This model may be "simpler", given the sophistication of idealized glacial models in the literature over the past decades, including the work of the lead author over the past decades. This linear model shows no oscillations, does not include Milankovitch forcing, and its relevance to the ice age problem is questionable. I do understand the lesson the authors are trying to derive here, but it seems to me that a sentence or two could make the point without this linear equation. My feeling is that our understanding of ice age dynamics is too sophisticated for this linear equation to provide any new or useful insights.