We were able to demonstrate quantitatively that the blue colour of the sky cannot be solely attributed to Rayleigh scattering. The influence of ozone on the blue colour of the sky is calculated for different viewing geometries, total ozone columns and an enhanced stratospheric aerosol scenario. Furthermore, the effects of polarisation, surface albedo and observer height are investigated.

Teleconnection patterns are important characteristics of the climate system; well-known examples include the El Niño and La Niña events driven from the tropical Pacific. We examined how spatiotemporal patterns that arise in the Pacific and Atlantic oceans behave under stratospheric aerosol geoengineering and greenhouse gas (GHG)-induced warming. In general, geoengineering reverses trends; however, the changes in decadal oscillation for the AMO, NAO, and PDO imposed by GHG are not suppressed.

This study is among the first modeling studies on stratospheric sulfate geoengineering that interactively couple a size-resolved sectional aerosol module to well-described stratospheric chemistry and radiation schemes in a global 3-D chemistry–climate model. We found that compared with SO₂ injection, the direct emission of aerosols results in more effective radiative forcing and that sensitivities to different injection strategies vary for different forms of injected sulfur.

Using a coupled Earth system model and radiative transfer modeling we show that the radiative forcing of a winter polar mesospheric ozone loss due to energetic particle precipitation is negligible. A climate impact of a mesospheric ozone loss as suggested by Andersson et al. (2014, Nature Communications) seems unlikely. A winter polar stratospheric ozone loss due to energetic particle precipitation leads to a small warming of the stratosphere, but only a few statistically significant changes.

This work focuses on solar radiation in the tropics, more specifically on ultraviolet radiation. From ground-based and satellite observations of the chemical state of the atmosphere, we were able to model the ultraviolet measurements measured in the southern tropics with a very small error. This is a first step to modelling and predicting future ultraviolet levels in the tropics from chemistry-climate projections.