There has been confirmation in the last two decades, through instrumental measurements onboard satellites, that the ‘solar constant’ does, as has long been hypothesized, vary over different timescales and with identifiable periodicities. This being the case, it is necessary to explore how these variations play a role in terrestrial climate change. While there is no consensus as to the best method for estimating past variations in solar output, it seems likely that over the last 500 years the sun has played a role in the changing climate. However, there is little evidence to suggest that changes in irradiance are having a large impact on the current warming trend.