In applying the injection stratospheric aerosol it’s important to know their impact into the environment, even it brings goodness on the one hand, but may also harm the other. Although the real goal of stratospheric aerosol injection is to cool the atmosphere and reduce climate change, but the study indicates that the method also gives an adverse impact on the environment. Geo-engineering with sulfate aerosols specifically can result in changes to the global ecosystem, the disruption of the hydrological cycle, changes in atmospheric circulation, continued ocean acidification and acid rain. UK Parliament Study state that increased sulphate aerosol concentrations in the stratosphere would catalyzes ozone destruction, and an increase in levels of acid rain would occur (emphasis added). The greatest harm, however, is thought to be the effect on precipitation levels.
According to the research Rasch et al., 2008, aerosols can stay longer in the stratosphere than they inject in the troposphere. A residence time of several years as opposed to several days means that fewer aerosols need to be introduced into the stratosphere in order to maintain the climatic effects. The characteristics of the stratosphere lead to the dispersion of the aerosols over an area larger than the launch site, causing a global, rather than local, effect, an important aspect of geo-engineering.
The majority of sulfate aerosols in the stratosphere exist in the form of sulfuric acid. The dispersion of aerosol particles over a large area results mainly from wind, though the lifetime of a sulfate particle is related to more variables, including meteorological conditions, particle size and concentration (Rasch et al., 2008). Sulphate aerosols have the potential to cause global changes in precipitation, temperature and water vapor, even if released from a singular location.
Stratospheric aerosol injection could also cause an increase in acid rain. Some aerosols find their way to the troposphere and hydrate to form sulfuric acid, leading to an increase in acid deposition in a variety of ecosystems (Kravitz et al., 2009). These increases will be most noticed in pristine as opposed to urban areas and areas with significant rainfall will be the most affected (Kravitz et al., 2009). Although sulfur is a necessary nutrient in some ecosystems, for other ecosystems it can be extremely harmful in excess quantities. Acid rain has led to a decrease in biodiversity in aquatic ecosystems and acidic soils can limit the amount of nutrients available to trees (Kannan & James, 2009). It is not possible to control the areas affected by acid rain because sulfate aerosols cause changes in cloud chemistry across the globe.
Another significant potential consequence of this scheme is an increase in ozone depletion. The seasonal ozone hole over Antarctica is caused by chemical reactions on the surface of water and nitric acid particles, and injecting sulfate aerosols would increase the surface area on which these chemical reactions can occur (Robock, 2008). As a result, the ozone hole would become larger, causing even more ultraviolet radiation to reach the Earth. UV radiation has negative effects and can cause skin cancer in humans as well as damage to DNA and photosensitizes in plants (Stapleton, 1992).
Finally, combating the rise in global temperature with stratospheric aerosols does not address continued carbon emissions, a significant side effect of global warming. The continued build up of greenhouse gases in the atmosphere leads to ocean acidification. The ocean uptakes a significant portion of excess carbon dioxide in the atmosphere (Robock, 2008) because when CO2 is dissolved it forms dissolved carbon dioxide, carbonic acid, bicarbonate and carbonate. Ocean acidification significantly affects marine ecosystems such as coral reefs, and would have repercussions through the entire biological chain (Robock, 2008).
BENEFIT | RISK |
1. Cool planet 2. Reduce or reverse sea ice melting 3. Reduce or reverse land ice sheet melting 4. Reduce or reverse sea level rise 5. Increase plant productivity 6. Increase terrestrial CO2 sink | 1. Drought in Africa and Asia 2. Continued ocean acidification from CO2 3. Ozone depletion 4. No more blue skies 5. Less solar power 6. Environmental impact of implementation 7. Rapid warming if stopped 8. Cannot stop effects quickly 9. Human error 10. Unexpected consequences 11. Commercial control 12. Military use of technology 13. Conflicts with current treaties 14. Whose hand on the thermostat? 15. Ruin terrestrial optical astronomy 16. Moral hazard – the prospect of it working would reduce drive for mitigation |
Figure 7.1: Table shown the benefit and the risk in using stratospheric aerosol injection
