A class of non‐linear climatic models giving rise to sustained oscillations is considered. The evolution equations are cast into a “normal form” which allows one to distinguish between two different types of quantities: a radial variable, which obeys a closed equation and has strong stability properties; and a phase variable which is extremely labile. It is shown that as a result of these peculiar stability properties, the disturbances or random fluctuations acting on the system tend to deregulate the oscillatory behavior. It is concluded that such a phenomenon is a basic reason for progressive loss of predictability.