Observations of terrestrial precipitation from the latter half of the 20th century are compared with precipitation simulated by the Parallel Climate Model to determine which external forcings have had a detectable influence on precipitation. Consistent with a previous study using another model, we found that the global mean response to all forcings combined was significantly correlated with that observed. A detection and attribution analysis applied to the simulated and observed precipitation indicated that the volcanic signal is detectable both on its own and in a multiple regression with other forcings. These results are consistent with the hypothesis that shortwave forcings exert a larger influence on precipitation than longwave forcings.