The School of Earth and Atmospheric Sciences Presents Dr. Antonello Provenzale, Institute of Geosciences and Earth Resources, CNR

How many Snowballs out there?Planetary climates are complex systems that include a multitude of stabilizing (negative) and destabilizing (positive) feedback loops. One of them, the ice-albedo feedback, is possibly causing multiple stable states in Earth’s climate, with the alternation between ice-covered conditions (the most extreme being the so-called Snowball) and warm states. Here, we adopt the view of climate as a dynamical system, strip down its complexity using a simple one-dimensional Energy Balance Model called ESTM and explore the conditions leading to bistability in the climate of Earth-like planets, briefly recalling the potential role of stochastic resonance.We shall then consider the effects of the ice-albedo feedback for a wide range of orbital and planetary parameters such as distance from the star, ellipticity, obliquity and atmospheric pressure. Other mechanisms for bistability will be mentioned, such as the vegetation-albedo and vegetation-moisture feedbacks, and the crucial role of atmospheric composition. Implications on planetary habitability will finally be considered.