Abstract.  The Earth undergoes long-term temperature cycles alternating between glacial and interglacial episodes. It is widely accepted that changes in the Earth's orbit and rotation axis cause variations in solar input which drive the glacial cycles. However, classic papers have clearly established that the response of the Earth's climate system to orbital forcing is not a simple linear phenomenon and must include nonlinear feedback mechanisms. One of these mechanisms is ice-albedo feedback, which can be modeled as a dynamical system. When combined with the cycles in the orbital elements and compared with the climate data, the model confirms that ice-albedo feedback is an important component of the Earth's climate.