The impact of solar variability on the middle atmosphere in present-day and pre-industrial atmospheres

By assessing both independently and simultaneously the effects of changing solar irradiance and atmospheric composition, we show that the ozone response is not a linear combination of the two factors. The key to this behaviour is again the NOx field which shows in a contemporary atmosphere, unlike in the pre-industrial atmosphere, a decrease in the lower stratosphere in response to a reduction in solar activity. The removal of NOx depends on the background humidity (via the reaction NO2 + OH⟶MHNO3), which is higher in the contemporary atmosphere. This result may help to explain the negative response of the lower stratospheric ozone to enhanced solar activity in the contemporary atmosphere, found in some analyses of satellite measurements.