Climatic impacts of stratospheric geoengineering with sulfate, black carbon and titania injection

• Published in: Atmospheric chemistry and physics Vol. 16; no. 5; pp. 2843 - 2862
• Main Authors: Jones, Anthony C, Haywood, James M, Jones, Andy
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 04.03.2016; Copernicus Publications
• Subjects: Aerosols; Atmosphere; Black carbon; Carbon; Carbon black; Carbon dioxide removal; Chemical properties; Climate change; Climate effects; Computer simulation; Environmental aspects; Environmental impact analysis; General circulation models; Geoengineering; Global temperatures; Greenhouse effect; Greenhouse gases; Historic temperatures; Injection; Mean temperatures; Methods; Observations; Optical properties; Precipitation; Radiation; Simulation; Solar radiation; Solar ultraviolet radiation; Stratosphere; Stratosphere radiation; Stratospheric circulation; Stratospheric sulfate; Stratospheric warming; Sulfates; Sulfur; Sulfur dioxide; Sulphur; Sulphur dioxide; Temperature; Temperature changes; Titanium dioxide; Ultraviolet radiation; Volcanic eruption effects; Volcanic eruptions
• DOI: 10.5194/acp-16-2843-2016
• ISSN: 1680-7324; 1680-7316

In this paper, we examine the potential climatic effects of geoengineering by sulfate, black carbon and titania injection against a baseline RCP8.5 scenario. We use the HadGEM2-CCS model to simulate scenarios in which the top-of-the-atmosphere radiative imbalance due to rising greenhouse gas concentrations is offset by sufficient aerosol injection throughout the 2020–2100 period. We find that the global-mean temperature is effectively maintained at historical levels for the entirety of the period for all three aerosol-injection scenarios, though there is a wide range of side-effects which are discussed in detail. The most prominent conclusion is that although the BC injection rate necessary to produce an equivalent global mean temperature response is much lower, the severity of stratospheric temperature changes (> +70 °C) and precipitation impacts effectively exclude BC from being a viable option for geoengineering. Additionally, while it has been suggested that titania would be an effective particle because of its high scattering efficiency, it also efficiently absorbs solar ultraviolet radiation producing a significant stratospheric warming (> +20 °C). As injection rates and climatic impacts for titania are close to those for sulfate, there appears to be little benefit in terms of climatic influence of using titania when compared to the injection of sulfur dioxide, which has the added benefit of being well-modeled through extensive research that has been carried out on naturally occurring explosive volcanic eruptions.