Hang on, there are downsides to Solar Radiation Management? Like an environmentalist once said, ain't that a kick in the head...

Dean Martin captured on a rumoured SRM flight mission 

In total, 240W of sunlight per square metre is absorbed by earth and is the principle method of how the Earth natural maintains or increases its temperature. Since the beginning of the industrial revolution, atmospheric CO₂ has almost doubled to 401.1ppm and at current trajectories is predicted to surpass the 450ppm ‘tipping point’ in which issues including ocean acidification and temperature increases may become so critical that they pass the point where by which they are salvageable. 

Caldeira writes that the doubling atmospheric CO₂ results in a radiative forcing of approximately 4Wm^-2. He then states that as a percentage of sunlight absorbed by the Earth per square metre, 1.7% of incoming solar radiation would need to be prevented from reaching the Earth’s surface to minimalise temperature rises. Thus, one would think that limiting this sunlight could help limit global warming. Enter, solar radiation management (SRM) – specifically Sulfur aerosols. For a detailed insight into the specifics behind this technique, see last weeks blog post.

So there you have it, a miraculous cure to save the planet from the impending doom of climate change. Well, not quite. Just like most quick-fixes, there are numerous severe stumbling blocks of this scenario, such as: resultant effects on regional climate; continued ocean acidification; the effects on clouds and the consideration about what happens if we change our mind and wish to stop this approach.

Oh, the weather outside is frightful…

A map of East Asia showing which areas are effected  by
reductions in precipitation, and by how much  (measured in mm).
http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0889.2009.00427.x/pdf

Alan Robock identifies a link between large volcanic eruptions and weakening African and Asian monsoons. In addition, Robock also points out the link between the eruption at Lake Fissure (Iceland) between 1783-84 and the following reduction of precipitation in Africa, Asia and Japan which resulted in the a famine responsible for the deaths of 25% of the Egyptian population.

S. Tilmes et al takes Robock's link further by discuss climate model experiments which have been used to simulate the consequences of Sulfur aerosol injections. They also write that when testing effects on regional weather systems with atmospheric CO₂ at pre-industrial levels that would result from SRM, there are significant impacts on precipitation and evaporation predominantly in the tropics and mid-latitude regions. They discovered a decrease in a mean precipitation of 3.6% over land. Specifically, the region hit with the greatest reductions in monsoon precipitation are East Asia (by 6%). This impact is extremely worrying as it would result in reduced yields for important crops in this region, leading to food shortages and a worsened quality of life for up to 1.5 billion people that live in this region. Thus, in light of this potential hydrological impact one could argue that it may be immoral to injection sulfate aerosol . 

When the world starts to shine like its had too much wine...it may be because Sulfer Aerosols offer no help with regards to the problem of ocean acidification

Up to 33% of Carbon Dioxide emissions from the human combustion of fossil fuels is absorbed by the ocean consequentially resulting in ocean acidification. As CO₂ is absorbed by the ocean it reacts with water to form Carbonic acid (H₂CO₃). This Carbonic acid dissociates within the water to produce bicarbonates releasing Hydrogen ions, hence causing an increase in acidification. The knock-on effect of this is that it would reduce the amount of carbon that could be stored in the oceans, which are the world's largest carbon sinks. doing so cause further global warming. Aerosol interjection offers no relief for this issue and would only allow this issue to worsen.

Everybody loves somebody...unless Sulfur aerosols divide international communities and starts a world war

Robock shines light on the political complexities tied to this stream of geoengineering. If an event were to happen, for example a world war, the aerosol injection programme would become seriously hindered. If there were to be a sudden halt to sulfur injections then we would see rapid global warming due to fact that greenhouse gas levels would have continued rising at exponential rates. Environmentalists such as Caldiera argue a rapid global warming process would cause exceedingly more damage to the worlds ecosystems than a more gradual global warming that we see happening today.

Furthermore, Robock suggests that if we were to proceed with this process, how do nations decide on whether a specific region such as East Asia should have to absorb the potential harsh impacts of this whilst other regions are relatively unscathed? This is an extremely valid point raised, and leads one to hypothetically argue that this could one day present the grounds for conflict itself if a nation being unfairly subjected to man-induced environmental alterations was rise up and fight against the environmental predicament that they had found themselves in. Therefore we must ask ourselves whether we would be truly comfortable with a global warming quick-fix that has the potential to one day be a proxy for future global conflicts.

In conclusion, although the analysis in last weeks blog post does suggest that injecting sulfate aerosols into the atmosphere would cool the Earth and restrict global warming. I feel that upon evaluating the side-effects and political uncertainties of this method, global governments should not seek to implement this form of geoengineering. Instead, we should investigate further other forms of geoengineering, such as solar mirrors or perhaps Carbon Capture and Storage. Both of which will be discussed in the continuation of this blog.