A new method named “permutation entropy” for detecting dynamical changes in time series was used to analysis the day-to-day temperature time series of north China from 1960a to 2000a. We detected three abrupt climate changes in the mid-1970s and early 1980s. Further analysis using Empirical Mode Decomposition to decompose the permutation entropy shows that the approximate 10a cycle is most important. So we can draw the conclusion that north China suffered three abrupt climate changes in the mid-1970s and early 1980s, and moreover, the the approximate 10a cycle induced the climate changes directly.