Empirical  reconstructions of  the Northern Hemisphere (NH) temperature in the last millennium based on multy proxy records depict small-amplitude variations followed by a clear warming trend in the last two centuries.  We use a coupled atmosphere-ocean model simulation of the last 1000 years as a surrogate climate to test the skill of  these methods, particularly at multidecadal and centennial timescales. Idealized proxy records are represented by simulated grid-point temperature, degraded with statistical noise. The centennial variability of the NH temperature is underestimated by the regression-based methods applied here, suggesting  that past variations may have been at least a factor of two larger than indicated by empirical reconstructions.