Implications of potential future grand solar minimum for ozone layer and climate

Abstract

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.

Ozone—climate interactions and effects on solar ultraviolet radiation

“…A new modeling study for the period 2000−2199, investigated the influence on ozone and climate by a hypothetical strong decline in solar activity that would last until 2199. 134 It was found that a reduction of about 15% in solar UV-C radiation would lead to a decrease in ozone production by up to 8%, which would overcompensate the anticipated increase in stratospheric ozone due to reduced stratospheric temperature and acceleration of the BDC. This would lead to a delay in the recovery of total ozone from ODSs, with global ozone not returning to pre-ozone-hole values before the end of the grand solar minimum.…”

“…135 The effects of changes in high energy electrons due to reduced solar activity have not been fully evaluated yet. 134…”

The historical ozone trends simulated with the SOCOLv4 and their comparison with observations and reanalyses

“…Besides a change in the relative strengths of the lower and upper branches of the meridional Brewer-Dobson circulation (BDC, Butchart et al, 2006) that resulted in ozone changes (Keeble et al, 2017;Li et al, 2009;Oman et al, 2009), there might be additional reasons for the decline in LSO, including the following: the recent reduction in solar activity (Arsenovic et al, 2018); the influence of halogen-containing very short-lived species and other gases unaccounted for by the MPA (Hossaini et al, 2015;Oman et al, 2016;Oram et al, 2017); increased emissions of inorganic iodine (Cuevas et al, 2018;Karagodin-Doyennel et al, 2021); increased aerosol loading (Andersson et al, 2015); unexpected increase in emissions of trichlorofluoromethane (CFC-11) violating the MPA (Fleming et al, 2020); altitude changes in the extratropical tropopause (Bognar et al, 2022).…”