Nonlinear models are considered in the report. The model describes the Caspian Sea level fluctuations, fluctuations of river basin runoff and water content. It is shown that sharp and unpredictable sea level fluctuations can be explained within the framework of the dynamic chaos theory. A simple model of the Earth's global climate is proposed. The model demonstrates the instability of the climate. The necessity of long-term and constant observations of the temperature regimes of the Caspian Sea and the Volga basin using aerospace monitoring is proved.
