I want to leave you with this video...

Change Needs to Happen

I suppose this is some sort of conclusion to my posts over the last few months. I've covered a variety of CDR and SRM techniques proposed along with some mitigation strategies also. I tried to deliberately avoid mitigation strategies such as wind and solar power as their pros and cons are already well established and I genuinely thought it would be a waste of your time to read posts about those schemes.

I'm of the opinion that geoengineering and mitigation are not, and shouldn't, be treated as mutually exclusive from another. When combined they can create a powerful 'team' to tackle anthropogenic climate change as a result of carbon dioxide increases. 
Personally I think that the best looking geoengineering scheme so far has to be that of carbon capture and storage, it posses the least amount of risk and can potentially lead to huge offsets in carbon dioxide and is currently where most investment lies. Other schemes are currently, very firmly planted in the modelling stage to assess their potential effectiveness. Even though modelling is a very powerful tool to synthesise observed data, there is a big limitation involved with it. As with any climate modelling (regardless of end goal) assumptions are made based on the theoretical relations and complex Earth system processes; which unfortunately makes models as weak as the data they're encoded with. The complexities of the Earth system, the ecology, biogeochemical cycling, and human systems will never be fully encoded into models.

Mitigation wise, I was genuinely interested in nuclear fusion as it is something that could change the face of the energy industry and the way we access power. However it seems ~30 years away from perfection (if perfection is achieved) and commercial usage is on a longer timescale. On shorter timescales it seems as if wholesale design changes in the construction industry have some promising initial results attached to it, there are some very clever and determined people in the construction industry and it is an industry which seems willing to change for the better! However as I've pointed out, sometimes mitigation schemes come with a human cost which is a total disgrace and shouldn't occur as a result.

I'm of my own personal opinion that the public, as a whole, are stuck in their ways when it comes to usage of finite resources. I simply think it comes down to a lack of education of the Earth and global change, lack of public interest in the subject which is understandable considering the current economic climate and poor investment into alternative resources making them much more costly than finite resources. 

I've really enjoyed researching the material for this topic, and there are so many more schemes and options out there which I haven't had the chance to cover as I'd have probably run into the hundreds in terms of posts. I therefore implore you to go out and take a look!

Just in reference to the wordle output of my blog, it was interesting to see 'et al' being the most commonly used words. It does imply that there is a large scientific community working in collaboration with one another to help tackle the issue of anthropogenic climate change.

Just remember this is The Only One We Have, so look after our Planet!

Thanks,
Sam.

Mt. St Helens

Relating to my last post here's a video of the eruption of Mt. St Helens in Washington state in 1980. It's quite long but it has some good footage so keep with it!

Problems with Deliberate Sulphate Injection

Now, if any of you reading this have any knowledge of stratospheric ozone loss then you will see an obvious problem. With injection of sulphate aerosols, it is expected that ozone depletion will occur (Crutzen, 2006), with recent model output showing a 15 to 60 year extension to the recovery of the Antarctic ozone hole (this is dependent on partical size and vertical extension). This is added to Arctic ozone losses expected between 60 to 80 DU (Dobson units) in 75% of all winters (Tilmes et al., 2008).

Modelling has also shown deliberate injection of sulphates could disrupt the Asian and African monsoons (Robock et al., 2008). Volcanic eruption responses suggest the Arctic Oscillation would be shifted to a stronger positive phase, associated with stronger westerlies and winter warming over Northern Eurasia and North America (Stenchikov et al. 2002, 2006).

Model predictions of the effects of a deliberate reduction of incoming solar radiation (mentioned in an earlier post about mirrors in orbit), including reduced precipitation, should be broadly applicable to sulphate aerosol loading.

Stratospheric aerosol loading will affect the ratio of direct to diffuse light. This will affect terrestrial (and potentially marine) photosynthesis (Rasch et al., 2008).

Rasch et al. (2008) has stated that further research on side effects is required, particularly into impacts on the biosphere. The uncertainties surrounding the effects of sulphate aerosol addition to the stratosphere are much greater and more meteorologically complicated than those relating to mitigating CO2 emissions (Tuck et al., 2008).

Sulphate Injection

Injection of sulphate aerosols into the stratosphere draws its inspiration on the natural (but imperfect) analogy of climate cooling from large volcanic eruptions such as Mt. Pinatubo in 1991 (Crutzen, 1991).

When large volcanoes erupt they emit sulphur dioxide into the atmosphere which reacts to form sulphate aerosols, which scatter shortwave and emit longwave radiation (Stenchikov et al., 1998).

Simple models studying the effects of sulphate aerosols have documented the temperature effects but do not take into account the change in stratospheric chemistry (Wigley 2006).

The effectiveness of geoengineered sulphate aerosol effectiveness and possible side effects have been judged by observational data (from volcanoes) (Stenchikov et al. 1998) (Crutzen 2006) atmosphere-ocean general circulation models (Robock et al. 2008), atmospheric chemistry modelling (Rasch et al. 2008) (Tilmes et al. 2008) and analysis of the radioisotope of Tungsten (185W) relating to atmospheric nuclear testing (Tuck et al. 2008).

A doubling of CO2 and its associated radiative forcing would require an increase in global albedo of 0.012 (assuming there is no absorbtion above the stratosphere) (Lenton and Vaughan 2009). The amount of sulphate aerosol needed is proportional to the size of particles and location of injection, these numbers range from 1.5 Tg S year−1 (Rasch et al. 2008) to 5 Tg S year−1 (Wigley 2006). Smaller particles (with a radius ∼ 0.1 μm) are more effective because they have no impact in the longwave, while the larger, volcanic-like particles absorb and emit in the longwave (Stenchikov et al. 1998).

The location of injection causes the residence time and special spread of particles in the stratosphere to vary greatly (Crutzen, 2006) (Wigley, 2006) (Rasch et al., 2008). According to Oman et al. (2005), Robock et al. (2008) and Rasch et al. (2008) residence time and global coverage is maximized when injections occur into the lower stratosphere over the tropics.

As for the mechanism of injection, artillery guns or balloons have been suggested as a delivery method for SO2 (Crutzen 2006); however due to microphysical and dynamic processes such a focused injection point could lead to coagulation of particles and subsequent fallout (Tuck et al. 2008) (Rasch et al. 2008). Consequently, others advocate a dispersed delivery method, such as high level aircraft to deliver the aerosol or precursor payload (Tuck et al. 2008; Rasch et al. 2008).

Promising yet again however the potential side effects here are huge which I will put in a later post (as per)!

Keeping CO2 stored

Geological storage options suitable for the injection of supercritical CO2 include depleted oil and gas reservoirs, enhanced oil recovery methods, deep unused saline water-saturated reservoir rocks, deep unmineable coal seams and enhance coal-bed methane recovery methods (IPCC 2005). For well selected, designed, operated and monitored sites, it is likely that 99% or more of the CO2 injected into these stores would be retained for 1000 years (IPCC 2005).

The IPCC (2005) have estimated that 460–3,030 Pg of carbon can be stored in geological reservoirs (oil and gas fields, unmineable coal seams and deep saline formations).

Oceanic injection of CO2 as been proposed as an alternative to geological storage, however there is assumed to be significant detrimental impact on ecosystems, so this method is generally considered to be unviable (Lenton, 2011).

The IPCC (2005) have ruled out other geologic storage options such as basalts, oil or gas rich shales, salt caverns or abandoned mines as having no significant contribution to make.

One more recent storage idea is to inject CO2 into deep-sea sediments at a depth where it is gravitationally stable (<3,000 m water depth and a few hundred metres sediment depth) (House et al. 2006). CO2  would stay in its liquid phase at such high pressures and low temperatures and would be denser than overlying pore fluid with CO2 hydrates forming a cap over the stored liquid CO2. 

Concerns highlighted include the unknown implications of the pore water displaced into the ocean and the importance of site selection as landslide events could release the CO2. In continental USA alone storage capacity for this method is measured at. >104 Gt CO2 (>2700 Pg C) (House et al. 2006). It is proposed that no verification or monitoring would be required due to the chemistry and physics of the over and underlying hydrates and fluids —an idea that may not be well received (Harvey and Huang 1995).

If this suggested form of carbon storage stands up to subsequent investigation, then when combined with storage options investigated within the IPCC’s SRCCS there may be sufficient capacity to store in excess of all the known fossil fuel resources of ∼3700 Pg C (IPCC 2007).

Next up, stratospheric aerosol injection.

Gotta catch it all!

As I explained in the last post, the Government is exploring the avenue of CCS, here's an overview of the capture process involved.

The capture process involves the use of a sorbent material (such as sodium hydroxide, NaOH) that selectively traps CO2 (Zeman 2007; Keith et al. 2006; Elliot et al. 2001).

The capture of CO2 can either be ambient (artificial trees) or an active flow (Keith et al. 2006). There is a greater cost in terms of energy attached to active flow, however it is not dependent on wind speed to work effectively.

The whole processes of regenerating the sorbent, compression and transport have an energy cost placed on them, so the net effect of this process on atmospheric CO2   will be less if met by fossil fuels (without CO2 capture and storage).

The capture of CO2 using bio-energy production (BECS) (bio-energy is explained in an earlier post) also generates pure streams of CO2 for storage. Both methods of capture remove atmospheric CO2 and share the same storage mechanisms; however we have discussed BECS with other land carbon options due to the similarity of constraints, such as land availability and possible ecosystem disturbance. BECS is estimated to have a better cost-benefit ratio than chemical air capture (Keith et al. 2006).

The size of the carbon sink for air capture and storage is solely dictated by how much societies are willing to pay, as it seems unlikely to have land or substrate availability limitations. The ultimate limitation surrounds storage capacity.

There are few side effects of air capture, aside from the energy and material costs of the infrastructure required if met by fossil fuels.

I’ll discuss storage options and amount of possible carbon stored in a later post….