The system-evolutionary approach to description, analysis, and estimation of climatic changes based on results of processing instrumental observations is discussed. Techniques for identification and technologies for analysis of rhythms in long-term changes of temperature regime are suggested. The techniques use a description of a sequence of states with seasonal (monthly) temperature extrema and the behavior of long-term changes in the length of cold and warm seasons. Examples and results of analysis of rhythmic temperature changes are given: the cyclic changes of winter temperature extrema with a period equal to the main solar cycle (179 years); features of the warming in Siberia with a stable tendency to formation of a regular rhythm. The interval estimation of regional warming rates based on the temperature increases in equitype phases of a cycle gives values between 0.6 and 1.4°C for the last 180 years.