1] We apply a multiple regression method to estimate the response to anthropogenic and natural climate forcings simultaneously from a number of paleo-reconstructions of Northern Hemispheric average temperature. These long records (600 to 1000 years) provide a unique opportunity to distinguish between different external influences on climate. The response to volcanic forcing is reliably detected in all reconstructions, and the simulated temperature response to volcanic eruptions compares favorably with observations. The response to solar forcing is detected in Hemispheric mean data only over some periods in some records, and appears weak. Although most records can be used only to the middle of the 20th century, the temperature response to CO 2 can be detected by this time in most records.