When viewed from the theory of chaos this electrical circuit begins to look like a member of a class of phenomena having random looking excursions in a region-in this case a frequency domain. We know that the real, global situation is complicated and not understood. What we want, as in any model, is to capture the gross features and then build in the complicated stuff later. In this spirit, it is global temperature that is the analog of electrical voltage. In other words, at the start a simple model may yield regular oscillations of temperature and as it becomes more realistic may show more non-linear variations.
Lets try and create the elements of a model in words and symbols.