Periodic solutions in low-dimensional climatic models

Classic climatic models use constitutive laws without any response time. A more realistic approach to the natural processes governing climate dynamics must introduce response time for heat and radiation fluxes. Extended irrev ersible thermodynamics (EIT) is a good thermodynamical framework for introd ucing nonclassical constitutive laws. Ln the present study EIT has been use d to analyze a Budyko-Sellers one-dimensional energy-balance model develope d by G. R. North. The results present self-sustained periodic oscillations when the response time is greater than a critical value. The high-frequency (few kiloyears) damped and nondamped oscillations obtained can be related to abrupt climatic changes without any variation in the external forcing of the system.