New high-precision measurements of the longitudinal magnetic field of Ap stars suggest the existence of secular intrinsic variations of the global magnetic field in some stars. We argue that such changes are apparent in the Ap star $alpha^2$ CVn in the time scale of $sim$ 10 years, which results from the analysis of literature data. Therefore, such an observation implies, that the rate of magnetic field evolution of Ap stars is much higher than was previously thought.
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