Ocean fertilisation....a viable approach?

Hey all,

So while we have looked at Geoengineering approaches aimed at reducing the amount of short wave radiation absorbed by the earth, other options include increasing the amount of long wave radiation emitted from the earth, through capturing and storing carbon!

Thanks to Viv’s lecture, the scientific basis for this post, has been provided. However, we will do a quick overview!

The carbon cycle is made up of a series of stocks and fluxes. Currently, the stock of CO₂  in the atmosphere is increasing, this is trapping increasing amounts of longwave radiation and causing temperatures to rise. Therefore, to increase the amount of longwave radiation emitted from the earth rather than trapped, CO₂  needs to be removed/transferred to other stocks.

The ocean is a large carbon sink. The Northern Hemisphere and Southern Hemisphere oceans store on average 2.2GtCyrˉ¹. Through the concept of the biological pump, shown in Figure 1, CO₂  is dissolved in the oceans and taken up by phytoplankton through the process of photosynthesis. When these organisms die, the organic carbon is transported to the sea floor.

Figure1:

Two decades ago, scientists realised that the amount of CO₂  absorbed by phytoplankton , and transported to the deep oceans could be enhanced by adding  iron, which is often a limiting nutrient for growth (Raven and Falkowski, 1999).  Numerous experiments have since been conducted in regions where waters are replete with light and  major plant nutrients, yet phytoplankton stocks are low. Several examples of these regions are shown in Figure 2.

Figure 2:

Although most experiments show noticeable decreases in dissolved inorganic carbon, carbon sequestration, whereby particulate organic carbon sinks to the ocean floor is limited. Once absorbed by the algae, only minimal amounts of carbon are sequestered while the rest is recycled back into the atmosphere. Several studies question whether iron fertilisation would make any significant reductions to the stock of CO₂ in the atmosphere. (Zahriev, et al., 2008; Martin, et al., 1994; Busseler, et al., 2004). Buesseler and Boyd (2003) estimate that the sequestration of the 30% of the carbon produced by human activities would require an area larger than the Southern Ocean. Consequently, more research is needed to determine the perfect conditions that may allow optimal carbon sequestration. However, there is a growing concern over scaling up experiments. Ocean ecosystems are still poorly understood in comparison to terrestrial ecosystems, tampering the food chain could lead to a domino of undesired impacts e.g. De-oxygenated waters, depletion of vital nutrients, all of which would severely affect fish stocks (Davis, 2006).

Geoengineering Projects - are they viable or just plain crazy!

Different groups define the term Geoengineering differently. Some use it to refer to any project that aims to modify the earth’s climate system, while others may only use the term to refer to projects that aim to reduce the amount of short wave radiation absorbed by the earth (Wigley, 2006); (Matthews and Caldeira); (Govindasamy and Caldeira). Either way, a wide variety of projects exist today that can be classified as Geoengineering projects. I have attempted to visually illustrate and group these projects in the image below (Figure 1). The red ring highlights the focus of the post today!

Figure 1

However, it is important to acknowledge that because Geoengineering is a field where ideas are constantly being generated, many proposals are probably not even known about. Moreover, since Geoengineering does have a stigma attached to it, most information on projects are available from sources other than scientific journals (Click here for some random Geoengineering projects found!)

However, when initially researching the field of Geoengineering the majority of the journals found were centered on activities aimed at reducing shortwave radiation; these activities being:

1. Using sunshades to reduce the amount of radiation reaching the top of the atmosphere
2. Using stratospheric aerosols or increased cloud cover to increase the albedo of the atmosphere

Brief explanations of theses activities may be obtained from youtube videos, newspaper articles and journals such as (Trenberth and Dai, 2007);(Wigley, 2006) and (Matthews and Caldeira, 2007). In fact, in numerous panel discussions regarding Geoengineering and even in journals, it is specifically mentioned that the entire stock of research on Geoengineering can be read during the course of one translantic flight, and that all the scientists advocating Geoengineering could fit comfortably in a university seminar room (Victor et al., 2009). This has heavily been reflected in the literature available, because while there are brief explanations of projects from a variety of sources, very few go into any substantial detail. While Geoengineering strategies are touched upon they are still in their early design stage. Several experiments have been conducted on a small scale but fear of academic discredit and due to the blurred boundary between experiments and actual long-term modification of the climate, prevent further full scientific investigations; this is especially true for the schemes aimed to reduce the amount of short wave radiation absorbed the earth.

The first strategy of placing sunshades in space has yet to be tested. It is an idea that has been met with resistance concerning cost, the location of the sun shades and the uncertainty regarding unforeseen impacts on the climate. Although there is consensus regarding the fact that it may cause a decrease in global temperatures, since incoming radiation significantly influences precipitation patterns, wind patterns, pressure systems etc, there is considerable uncertainty regarding the extent to which sunshades may do more harm than good. However, initial calculations have been made:

Lenton and Vaughan (2009) make coarse calculations on the cost and effectiveness of using sunshades in space. They calculate that to offset a doubled pre-industrial atmospheric concentration of CO2, it is assumed that a reduction in incoming solar radiation by 1.8% is required. However, this calculation is based on a static radiative imbalance. In reality, CO2 emissions are increasing by approximately 2ppm/yr, consequently, the radiative imbalance is set to continue increasing. Therefore, to offset the current radiative imbalance and future increases in CO2 then solar shades with a surface area of approximately 35700km2 need to be added every year to space. This equates to approximately 15500 launches per year, carrying 800 000 space flyers of 0.288m2. To me this sounds a little crazy.....but investigations are still being conducted! But at the same time, you can’t help wonder, what are the C02 emissions produced from all those rocket launches?!

In terms of the second project aimed at reducing the amount of incoming radiation absorbed, injecting aerosols into the atmosphere has also been met with considerable resistance. However, the difference with this scheme, is that experiments on both local and global scale have shown its effectiveness at reducing global temperatures (see Figure 2 below!)

Figure 2

The idea of injecting aerosols into the environment originated from past natural experiments. Rapid reductions in temperature have been experienced several times in the past (as shown in Figure 2), and this has been a result of volcanic eruptions injecting several tonnes of particles into the atmosphere. The eruption of Mount Pinatubo in 1991, injected sulphate aerosols into the stratosphere and generated a cooling of a few tenths of degree for several years after the eruption. Therefore, drawing on the climatic effect of large volcanic eruptions, by extension, through purposely injecting sulphate aerosols into the atmosphere then the cooling experienced after 1991 may be replicated. This could consequently compensate for some or even all of the climate warming that has been induced by the emission of GHGs.

Unlike the idea of putting sunshades in space, the concept of injecting particles into the stratosphere in order to increase the albedo of the atmosphere and reduce the amount of short wave radiation absorbed the earth has been naturally tested. This has allowed calculations to be made, the model simulations to be run. Some of the results show the following:

Matthews and Caldeira (2007) simulated the changes in surface air temperature (see Figure 3a and 3c) and precipitation (see Figure 3b and 3d) for the year 2100 relative to 1900. Figure 3a and 3b show the results from model simulations using the IPCCs development scenario A2 while Figure 3c and 3d show model results  when including Geoengineering projects. The results shown in Figure 3c and 3d are a result of a globally uniform factor being applied to incoming solar radiation, as a result of Geoengineering activities. The results show that there is a greater absolute reduction in incoming solar radiation in the Tropics relative to the poles. Consequently, global cooling is not felt uniformly. However, it must be noted that the results shown do not incorporate the technical difficulties and also the scientific uncertainties regarding the deployment and effectiveness of Geoengineering schemes, aimed at reducing incoming solar radiation.

Figure 3

The Figure 3 shows that significant reductions in temperatures may be achieved. However, there are several factors to consider:

1. A rapid decrease in global temperatures due to the injection of aerosols may be met with an even faster rate of increase in temperature if injections are ceased and Geoengineering practices are stopped. This warming rebound may result in several years of very rapid climatic change. This is seen in the diagram shown in Figure 4. The diagram also shows the effect of multiple sequential eruptions of Pinatubo, every year, every two years and every four years. This  highlights how continuous injections of aerosols will be required to meet the required amount of cooling.  
2. The effect on the globe will not be uniform. Depending on where the injections are made, and the trajectory of the particles, this will subsequently affect the extent of cooling experienced in different regions around the globe. This may not suit the interest of all nations.
3.   Even though the injection of aerosols will provide the desired outcome of a reduction in temperature, the impact that it may have on other climate variables in unknown. Moreover, any further health risks are also unknown. Moreover, considering the characteristic of rapid temperature increase if geoengineering practices are stopped, this may lead to significantly damaging impact

Figure 4

Overall, even though the majority of research is centered on these two concepts of reducing the amount of incoming radiation absorbed, the studies highlight how research is still in its infancy. Subsequently, the impact that these Geoengineering projects may have on the planet is still heavily uncertain. Consequently, there is considerable risk. However, natural experiments and results from model simulations has shown that there is potential, that if one day the climate was to experience a tipping point then these schemes may act as an insurance policy, a last resort. But the question is when do we say enough is enough? When do we say that climate change is already having a devastating impact on or lives and it is time to resort to drastic measures? You and I may not feel it is time but what about the people living on the small islands facing rising sea levels? Or the people in Bangladesh even? Or the people living in Africa facing water scarcity? Or what happens when China or India feel they no longer want to curb emissions but the prospect of further increases in global temperature will cripple their ability to provide food for their growing populations? What happens when they get tired of the US and the UK and other developing nations telling them that they have to cut emissions when we won’t even make drastic cuts to our emissions!? (the Australia agreed on reducing emissions by 5%!) Mitigation of global warming is an international effort; however, the use of Geoengineering to curb emissions is not......ergo....the concept of Geoengineering becomes a ticking timebomb! (To be continued.....)