Abstract. Continued anthropogenic greenhouse gas (GHG) emissions are expected to cause further global warming throughout the 21 st century. Understanding potential interferences with natural forcings is thus of great interest. Here we investigate the impact of a recently proposed 21 st century grand solar minimum on atmospheric chemistry and climate using the SOCOL3-10 MPIOM chemistry-climate model with interactive ocean. We examine several model simulations for the period 2000 -2199, following the greenhouse gas scenario RCP4.5, but with different solar forcings: the reference simulation is forced by perpetual repetition of solar cycle 23 until the year 2199, whereas the grand solar minimum simulations assume strong declines in solar activity of 3.5 and 6.5 W/m 2 with different durations. Decreased solar activity is found to yield up to a doubling of the GHG induced stratospheric and mesospheric cooling. Under the grand solar minimum scenario tropospheric temperatures are also 15 projected to decrease. On the global scale the reduced solar forcing compensates at most 15% of the expected greenhouse warming at the end of 21 st and around 25% at the end of 22 nd century. The regional effects are predicted to be stronger, in particular in northern high latitude winter. In the stratosphere, the reduced incoming ultraviolet radiation leads to less ozone production by up to 8%, which overcompensates the anticipated ozone increase due to reduced stratospheric temperatures and an acceleration of the Brewer-Dobson circulation. This, in turn, leads to a delay in total ozone column recovery from 20 anthropogenic chlorine-induced depletion, with a global ozone recovery to the pre-ozone hole values happening only upon completion of the grand solar minimum in the 22 nd century or later.