I don't know what an unstable loop is. I was referring to the well defined cybernetics concept of feedback loop[1] which is simple: a feedback loop occurs when

I don't know what an unstable loop is. I was referring to the well defined cybernetics concept of feedback loop[1] which is simple: a feedback loop occurs when the output of a system applies to the input of the system. In the discussed case it is a positive feedback loop as outputs adds itself to input [2]. I don't understand what you are trying to say by pointing out earth was warmer and cooled down, but you can read about positive and negative feedback loop during glacial period on wikipedia[3]. [1]: https://en.wikipedia.org/wiki/Feedback#/media/File:General_Feedback_Loop.svg https://en.wikipedia.org/wiki/Feedback#/media/File:General_F... [2]: https://www.annualreviews.org/doi/full/10.1146/annurev.energy.25.1.441 https://www.annualreviews.org/doi/full/10.1146/annurev.energ... [3]: https://en.wikipedia.org/wiki/Ice_age#Positive_and_negative_feedback_in_glacial_periods https://en.wikipedia.org/wiki/Ice_age#Positive_and_negative_...