Stratospheric sulfate aerosols

This is a solar radiation management technique; and from what I've been reading this idea seems very promising.  A previous post of mine summarised the technique to have high effectiveness - the technology is also developed and ready to be implemented.  There were however concerns over safety and cost.  Luckily I found some facts to rubbish these allegations:
- Crutzen (we all know and trust him because he termed the anthropocene) estimated the technique to be x100 cheaper than cutting CO2 emissions ($25–50 billion a year).
- Sulfur injections into the stratosphere are a natural phenomena (i.e volcanic eruptions) and there is substantial evidence these cool the planet.

Basically the science behind it is, injecting a sulfide gas (H₂S or SO₂ mainly) into the stratosphere.  In fact any aerosols scatter sunlight, but sulfides are advantageous as they can be introduced as gases (Katz 2010) meaning particles don't clump together, hence enhancing the albedo effect. Once up there, the particles scatter incoming solar energy before it reaches the surface.  Apparently, reducing solar input by just 2% balances out the effect on global temperatures of a doubling of CO₂ (The Royal Society 2009).

There is some debate surrounding the most effective and feasible way of inserting the gases at such a great height.  Currently, it has been proposed this could be achieved by aircraft, military guns or high-altitude balloons.  This aspect is important, as the lifespan of aerosols in the trophosphere is short due to them being washed out.  Additionally, more research is required into where on Earth they should be delivered in order for them to be evenly distributed around the globe.

Unfortunately there are some risks and side effects associated with this method of solar radiation management, including:

• Acceleration of ozone depletion
• Increase in drought severity
• Possibly only short-lived
• Requires continuous injections of sulfides
• Altering the appearance of the sky and sunsets
• Dry fallout of particles

However more work is required in order to examine these side effects more thoroughly.  I think a disadvantage of this method is that as it is not widely used (yet), and studies into the effects are heavily based upon modelling; which contain errors.  I'm going to look at a paper which investigates one of these associated negative effects (the amount of sulfur deposition to the Earth's surface) using modelling to further evaluate this technique.  At the moment though if I had $25-50 billion I'd definitely pay for this!


Also this is good, 20 reasons why geoengineering may be a bad idea.  But it still didn't change my mind!  I don't think emission mitigation is going to be enough to help us in the future.  Personally I'm not bothered if the sky looks a little whiter, as long as it keeps the world cooler!

Cow Power

Just read an article on converting cow manure to electricity...
I like this idea!
The farmers benefit from selling the energy their cows produce, although how long it takes to breakeven after they've invested in the (expensive) equipment I'm not sure.
I've always entertained the idea of renewable energy; so maybe cows are the key to reducing our carbon emissions?  Although I'm a bit worried the article overlooks the fact cows produce crazy amounts of methane! 

SOIREE/EisenEx OIF paper

To accompany the previous post on ocean iron fertilization I've looked at a case study to evaluate the effectiveness of the technique.  A paper published by Bakker et al. compared the 2nd and 3rd OIF experiments in the Southern Ocean and examined the effects added iron had upon biological carbon uptake in surface waters. 

The location of the two experiment sites are illustrated below:

   


















SOIREE
The SOIREE experiment took place for 13 days in Feburary 1999 in a stable hydrographic setting.  A ship released iron and a sulphur hexafluoride tracer to create a 50km² iron-enriched patch.  This process was repeated a further 3 times on the 3rd, 5th and 7th days with the total amount of iron added totalling 1745kg, raising the total iron concentration in surface waters to between 2.5-4nM (x10 higher than before any iron addition).
Storms occurred on days 1 and 4 which mixed iron to depths of ~60-75m.  Results show a phytoplankton bloom was stimulated, and as a result CO₂ in surface waters reduced from day 4 onwards at a rate of 3.8μatm day⁻¹.  Reduction of DIC occurred evenly above 50m depth, but no change in DIC was recorded below this.
A 'top hat effect' was produced; where CO₂ reduction was most efficient in the centre of the patch, which highlights the importance of selecting a site for future experimentation; focusing on optimum areas of fertilization as the centre of the top hat.

EisenEx
The EisenEx experiment occurred for 22 days in November 2000 in a cyclonic eddy, and overall 2340kg of iron was added to surface waters on days 0, 8 and 16.  The site experienced severe storms on days 5 and 13 and resulted in deep mixing of iron.  Algal growth was limited by heavy cloud cover, and only a small reduction in surface water CO₂ was observed until the day of the first storm.  Iron was shown to have mixed to depths of 76m after 7 days and additionally the size of the patch was stronlgy enlarged.
The figure below illustrates the amount of surface water carbon is being removed:

Surface water CO₂ remained constant for several days after the storm, and a small decrease is shown after 7 days.  Days 8-12 show surface water CO₂ decreasing at a steady rate, and a storm on day 13 removes some of the surface carbon by transporting it to greater depths.  In contrast to the SOIREE experiment, EisenEx surface carbon did not decrease at a steady rate..

Climatic influences were more apparent in the EisenEx expt; with wind speed and atmospheric pressure both affecting the air-sea transfer of CO₂.  This experiment has shown there is a link between the magnitude of the air-sea gradient and the reduction of surface water CO₂ once iron fertilization has ensued, illustrating again the need for careful site selection for OIF experiments.

Total biological DIC reduction
Despite the differences in patch size, mixed layer depth and the air-sea gradient the total removal of DIC by organisms was on a comparable scale.  After 12 days the SOIREE experiment had reduced DIC by 1389 tons, and the EisenEx expt by 1433 tons respectively.

Conclusion
The experiments show differences in the removal of surface water CO₂ as a result of different mixing regimes (intensity and depth), but similarities in the amount of DIC uptaken by biological activity.  This shows the mixing regimes has little or no effect on overall biological uptake - which could also be important in terms of site selection in future experiments.  However, the EisenEx experiment shows as a result of mixing, the area was 4x more efficient at drawing down CO₂ from the atmosphere.
The experiments failed to quantify how much carbon actually left the surface ocean; and furthermore how much of this was actually sequestered.  It was suggested however that more carbon may have been stored longer-term at the EisenEx site due to it being located closer to subduction sites; where surface water sinks and mixes with deeper water, creating a greater potential for atmospheric CO₂ storage and transport from the surface.
The concluding remarks of the paper focus on how hard it is to accurately quantify carbon storage, the efficiancy of carbon removal and DIC uptake from biological activity.  Currently a suitable solution has still not been applied to solve these issues.  The experiments were useful in terms of highlighting the importance of site selection; not only in terms of wind and atmospheric pressure but also the opportunity for transport to lower depths.
I have decided I am undecided as to whether this is a good technique for fixing climate.  Probably not; although obviously it is effective in the short-term.  It has the advantage of using technology already developed but I am doubtful in terms of it's use in long term climate change mitigation and the uncertainty surrounding the quantities of carbon actually being stored.



Bakker, D.C.E. (2005), 'Iron and mixing affect biological carbon uptake in SOIREE and EisenEx, two Southern Ocean iron fertilisation experiments', Deep Sea Reasearch I: Oceanographic Research Papers, 52, 6, 1001-1019.

"Give me a half a tanker of iron and I will give you another ice age" - John Martin 1991

A bit of an overstatement, but nevertheless.  Ocean iron fertilization (OIF) is a CDR technique which involves depositing large amounts of iron into the surface ocean as a way of enhancing the biological pump.

For those who are unfamiliar with the concept of the biological pump; in essence it's the process of phytoplankton uptaking dissolved inorganic carbon during photosynthesis, and some of this fixed carbon being deposited to the deep ocean as dissolved organic matter (DOM).  However, only 1% of all carbon taken up at the surface is actually eventually sequestered into ocean sediments due to other processes acting on it in both the surface and deeper ocean which turns it back into dissolved inorganic carbon.

In 1990 John Martin hypothesised that by adding iron to nutrient-rich but low productive (HNLC) ocean regions, it would stimulate phytoplankton blooms, which would drawdown significant amounts of atmospheric carbon dioxide into the oceans and increase the rate at which carbon is sequestered into the deep ocean.  HNLC regions were identified in the northern and equatorial Pacific and the Southern Ocean, and since 1993 12 experiments have occurred in these regions.

(WHOI 2008)

Ideally, the Pacific is easier to work in due to calm seas, lots of sunlight and warmth which stimulates algal growth.  However, the Southern Ocean contains 3-5 times higher nutrient levels - although lacks warmth and sunlight for many parts of the year.
It is worth noting these experiments were only on a small scale, but results showed OIF did indeed stimulate algal blooms temporarily (IPCC).  However, the experiments are somewhat inconclusive in the way many important questions were raised but remained unanswered.  Most importantly, it was difficult to tell exactly how much extra carbon was sequestered as a result of enhanced algal blooms, and the side-effects of such an experiment were a cause for concern (although no ecological impacts were observed during these experiments, but they were only on a small scale (WHOI 2008)). 

Potential negative consequences of OIF

• Shift in phytoplankton species, from small phytoplanktonic species to a diatom dominated state (Greenpeace), resulting in possible changes in the food web.
• Nutrient depletion in surrounding waters (WHOI 2008).
• Deoxygenation of surface waters; which may cause a negative effects on other marine organisms.
• Development of harmful algal blooms.

Considering this 2 decades on OIF still remains a controversial idea.  Despite the possible drawbacks and hazards associated with this method, many scientists and (increasingly) private companies back the idea and are keen to develop more experiments - this time on a much larger scale in the hope of obtaining more clear results.  These parties argue our present knowledge of the ocean is somewhat unclear; and further experimentation is in everyone's interest.  Additionally; future proposed projects are still on too much of a small scale to cause lasting environmental damage.

In conclusion to using OIF as a CRT then, it is clear it is not as effective as early models predicted, and poses many difficult questions.  A major drawback is the fact it is so difficult to measure not only how much more carbon is actually being removed from the atmosphere, but how much of this is actually being sequestered.  Storing carbon in larger organisms or algae in the middle-depth waters is potentially a short-term solution to employ whilst better technologies are developed, but will only remain here for a few decades at most.  Obviously this means OIF is not suitable for being considered as a long-term technique to stopping environmental change (Davis 2008).  The fact only 12 experiments have been employed in over 2 decades suggests lack of interest in the method, and it is possibly difficult to obtain funding for something which does not have guaranteed success.  The technology has not yet seemed to have advanced very much since John Martin's declaration of the iron hypothesis in 1991, so maybe it is time to develop more sophisticated and advanced techniques of CDR?

The future....

More experiments are being considered by both scientists and private companies; this time on a bigger scale with around 100 tons of iron involved (WHOI 2008).  Certainly better monitoring technologies are required to measure and improve the knowledge of sequestration.

“You might make some of the ocean greener by iron enrichment, but you’re going to make a lot of the ocean bluer.” - Robert Anderson.  Maybe OIF will have to be considered as a trade-off!

An introduction to geoengineering

Geoengineering has been termed "the deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change" (The Royal Society 2009).  Although I'm aware of certain techniques being developed to mitigate climate change over the past decade or so; I didn't realise there were quite so many technologies being innovated and tested.  I find the paper produced by the Royal Society in 2009 is referenced in lots of the papers and articles I'm reading about this subject and it provides a good summary of the main geoengineering proposals. 

Large-scale methods being developed to save the planet fall into two main categories - carbon dioxide removal (CDR) and solar radiation management (SRM).  The main difference between the two is that SRM techniques are concerned with reflecting or deflecting solar energy mainly in the stratosphere, thus reducing the amount of thermal energy reaching the atmosphere and to Earth.  In contrast, CDR techniques actually remove the amount of carbon dioxide in the atmosphere to cool the Earth by allowing infrared waves to exit more easily.  Below I found some diagrams summarising some of the methods being developed:

(Kerr 2006)

Overall SRM tend to be more favourable in terms of readiness and effectiveness.  However, these can be considered as more short-term techniques as they only limit or decrease global temperatures.  Studies suggest SRM produces unintentional environmental effects in the way of altering global weather patterns and ocean currents, which could produce ill-effects in some parts of the globe.  More research is required into the effects SRM will have upon global climate patterns, their sustainability and other potential risks .
CDR tends to be considered safer; but obviously a greater deal of research and refinement is required in order to be employed on a global scale.  Effectiveness of CDR techniques is considered to be lower, but this may be due to the fact removing carbon dioxide from the atmosphere will take years or decades before global temperatures reduce noticeably.

(Maynard 2009)

CDR techniques may be more acceptable in some societies due to the fact they have less associated risks.  Additionally they are more sustainable in the way they actually remove the carbon dioxide currently residing in the atmosphere - CDR techniques coupled with reducing emissions may be the key to fixing the climate due to the fact they are sustainable.  However, the extent of the error bars provided on the diagram above illustrating uncertainties show how much more work needs to be applied in terms of developing and refining the methods we already have available, therefore the future is still uncertain.

This aside, although geoengineering is obviously going to be a big part of the future in terms of mitigating climate change; I think it is also very important to continue to promote public awareness of the issue and to continue efforts to reduce greenhouse gas emissions as opposed to just applying technology to try to cool the planet.  Geoengineering creates moral issues in terms of lessening the pressure of emissions reductions, but I'll look at this debate another time.

My first post (scary)

Hello, welcome to my blog :)  I've decided to blog about what we in the world are doing to try to mitigate and reverse the effects of environmental change.  I'm looking on a global, national and local scale - and as well as large scale geoengineering techniques, I'll find out what's being done on a small scale and can be achieved by individuals. 

I'm hoping by the end to form some sort of opinion about which techniques might be best by researching the techniques and evaluating case studies which have adopted them.  Hopefully tomorrow I'll have something academic to write about as well.  Goodnight!