[source] Climate engineering and solar radiation management in general are controversial, and pose various problems and risks. However, certain problems are specific to, or more pronounced with this particular technique.[23]
• Ozone depletion: is a potential side effect of sulfur aerosols;[24][25] and these concerns have been supported by modelling.[26] However, this may only occur if high enough quantities of aerosols drift to, or are deposited in, Polar stratospheric clouds before the levels of CFCs and other ozone destroying gases fall naturally to safe levels because stratospheric aerosols, together with the ozone destroying gases, are responsible for ozone depletion.[27]
• Whitening of the sky: Stratospheric aerosols have the potential to whiten the sky and cause more colorful sunsets, dependent on the amount being sprayed.[28] According to a study on cleaner air, resulting solar brightening has been responsible for an increase in corn production over the past 30 years.[29]
• Tropopause warming: and the humidification of the stratosphere.[25]
• Regional warming: Based on the results of the 2014-2015 Geoengineering Model Intercomparison Project, a model with a standard stratospheric aerosol injection scenario, temperatures in the tropics would cool, and higher latitudes warm, ice sheet, and Arctic sea ice decline would still continue, albeit at a reduced rate. Extreme temperature anomalies would also still increase, but to a lesser degree. In regards to these model results, the author of the study Alan Robock noted:
« If geoengineering were halted all at once, there would be rapid temperature and precipitation increases at 5–10 times the rates from gradual global warming. »[30]
• Stratospheric temperature change: Aerosols can also absorb some radiation from the Sun, the Earth and the surrounding atmosphere. This changes the surrounding air temperature and could potentially impact on the stratospheric circulation, which in turn may impact the surface circulation.[31]
• Regional hydrologic responses: Based on the results of the Geoengineering Model Intercomparison Project, there would be a reduction in the global average precipitation around the world, particularly in summer monsoon regions.[30]