This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/2014JD022022 ; It has been suggested that the Sun may evolve into a period of lower activity over the 21st century. This study examines the potential climate impacts of the onset of an extreme ?Maunder Minimum like? grand solar minimum using a comprehensive global climate model. Over the second half of the 21st century, the scenario assumes a decrease in total solar irradiance of 0.12% compared to a reference RCP8.5 experiment. The decrease in solar irradiance cools the stratopause (~1 hPa) in the annual and global mean by 1.4 K. The impact on global mean near-surface temperature is small (~?0.1 K), but larger changes in regional climate occur during the stratospheric dynamically active seasons. In Northern hemisphere (NH) winter-time, there is a weakening of the stratospheric westerly jet by up to ~3-4 m s1, with the largest changes occurring in January-February. This is accompanied by a deepening of the Aleutian low at the surface and an increase in blocking over northernEurope and the north Pacific. There is also an equatorward shift in the Southern hemisphere (SH) midlatitude eddy-driven jet in austral spring. The occurrence of an amplified regional response during winter and spring suggests a contribution froma top-down pathway for solar-climate coupling; this is tested using an experiment in which ultraviolet (200?320 nm) radiation is decreased in isolation of other changes. The results show that a large decline in solar activity over the 21st centurycould have important impacts on the stratosphere and regional surface climate. ; LJG and ACM were supported by the National Centre for Atmospheric Science's Climate Directorate. ACM also acknowledges support from the ERC ACCI project no. 267760 and an AXA Postdoctoral Fellowship. SI and AAS were supported by the Joint DECC/Defra Met O ce Hadley Centre Climate Programme (GA01101). LJG and JAA were supported by a grant from the National Environmental Research Council.