CDR: Ocean Fertilization

We have introduced in this post the concepts of both types of geoengineering: Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR). However, all of the geoengineering techniques we have discussed are SRM. This means they decrease the amount of radiation absorbed by the Earth. Although they can be very effective, their side effects are dangerous and unknown.

However, the main problem of SRM techniques is that they do not address the problem of the excess of CO2 and everything this brings: e.g. ocean acidification. We discussed the problem of ocean acidification in a past post.

CDR techniques aim to reduce the amount of CO2 in the atmosphere. Currently, more than 25% of the CO2 emitted by us is absorbed by the oceans. If we could make this percentage higher than 100%, then we would be reducing the amount of CO2 in the atmosphere.

One big consumer of CO2 in the ocean is phytoplankton. Phytoplankton in the upper layer of the oceans use the CO2 dissolved in water for photosynthesis. This CO2 is then dragged to the bottom of the ocean by gravity in the form of dead algae or other waste from the corresponding food chain. Afterwards, this waste is used as food by bacteria or other beings at the bottom of the sea, and they release the CO2 by respiration to the deep water in the ocean. This is a simplification of the process called biological pump, process in charge of sending CO2 from the upper ocean layer to the bottom layer of the ocean.

The thought now is, if there were more algae in the ocean, the biological pump would accelerate consuming more CO2 from the upper ocean, and therefore from the atmosphere, presumably. In order to increase the population of algae, one has to study its limitant factor. The proportion needed is 106C:16N:1P:0.0001Fe (Sarmiento et al, 2004), so the most effective way would be fertilising the ocean through the addition of iron. A lot of experiments have been made to see if this addition would actually make the algae population bloom (Martin et al, 1994), all having very positive results at first, but this bloom was usually controlled by other limitant factors, zooplankton, or other marine factor trying to regain an equilibrium to its previous state. There are some regions, however, like the southern ocean (Shepherd et al, 2009), where the limitant factor is known to be iron and ocean fertilisation through iron would be most effective there. Therefore, iron fertilisation in the southern ocean war further studied by Buesseler et at, 2004. The results are shown in the diagram below.

Shows the flow of CO2 in and out in the first 50m of water and after the 100m before and after using the iron fertilization technique. Source: Buesseler et at, 2004

However, many side effects are yet unkown. These are thought to include large effects in marine ecosystem, or even changes in other dynamics that could lead to severe climatic problems (Lawrence, 2002), and changes in the ocean circulation due to changes in the sea surface temperature or salinity. Also, other chemicals assosiated with this procedure are thought to damage the ozone in the stratosphere and lower stratosphere, therefore increasing the damages made to the ozone layer (Solomon et al, 1994).

A phytoplankton bloom in Argentina's coast as seen from space. Source: Wikipedia. 

Aditionally some side effects that could be either good or bad are the following. This procedure could lead to a neutralization of ocean acidification (Cao and Caldeira, 2010) in the surface water of the ocean, but it will surely further acidify the deep ocean (because it is pumping more CO2 to the deep ocean). Furthermore, the procedure is known to produce CH3Cl, CH3Br, and CH3I, which act as Cloud Condensation Nuclei (CCN) (Lawrence, 2002), (see previous post).

Something worth mentioning is that this process, just as the stratospheric injections, is made naturally sometimes in extreme events as discussed in a volcanic eruption by Achterberg et al, 2013.

Video: The world's CO2 yearly emissions

This post is just to share with you a video I recently discovered and absolutely loved.

It is a video from Vox that takes images from NASA that show the the yearly emissions of CO2 and explains them. It is very interesting and illustrative. Make yourself some time to watch it!

Meanwhile: some politics...

The IPCC report was a hit worldwide. Every newspaper made a review of the main outcomes of the report (mainly that we have to stop fossil fuel emissions now). Citizens are becoming more and more aware of the threat presented to us nowadays and the important moment in which we stand. Our fate will depend on the decisions we make today.

If these decisions were to be made by the climate scientists, the world would surely be saved. The problem is the decisions are obviously made by politicians, who are primarily interested in economical or other types of growth.

A lot of treaties were made trying to address the problem of climate change, but they were never very successful. In December 2014 the last UN climate conference was held in Peru, where, for the first time, 196 countries made an agreement. Will these agreements solve the problem of climate change? Doubtfully.

So, what were the outcomes of this conference in Peru? What did the 196 countries agree to do? They all must, in the next six months, present some sort of plan describing how they are going to help fight climate change in the future. After this, a climate agreement will be signed in the end of 2015 in Paris, according to these plans so as to make them official.

The key concept of this conference: freedom. All countries will have total freedom on their "plan" to fight climate change. It can be as strict or as relaxed as they want it to be. Also, another key fact is that, after the Paris conference, if countries do not comply to their "plan", there will be no penalty.

If we observe previous agreements like the Kyoto Protocol, we could see that by being strict upon promises to be made, countries like China or India refused to sign. Also, others, like Canada, just abandoned the protocol when they realised they could not comply what they had agreed to. So, the freedom in the current Peru agreement could be the reason why we got 196 countries to agree.

Now, as political scientist David Victor said in 2008, we have to apply the "bottom up" technique. We have agreed in the bottom, i.e. the most relaxed of all possible agreements, with total freedom, but at least we are all together. This could be the start of some political improvement.






And these totally relaxed agreements will be signed in the end of 2015, and with no punishments if not complied...

...Meanwhile, the CO2 levels keep rising, and the clock keeps ticking...


Suddenly the geoengineering options seem better than they did before, don't you think? We might need it, and if that moment ever comes, we better be as prepared as possible. 
  

Increasing Cloud Albedo

We have already discussed that increasing albedo is a very important way of Solar Radiation Management (SRM). We have studied how to increase albedo in cities, crops, desserts. We mentioned the fact that people are still studying how to increase albedo in oceans (given that they are the ones that have lower albedo, and they occupy a great amount of the Earth's surface, and would therefore be the best candidates), but these studies have not yet been published. In the last post we discussed the possibility of injecting particles to the stratosphere so that they reflect incoming radiation.

However, there is something clearly missing. Something that naturally blocks sunlight away from us (mainly here, in England, for example :( ). Of course, clouds!!! However, this is not to be treated so easily. Clouds have both powers. Some allow the income of solar radiation towards the Earth and reflect infrared radiation from the Earth back to the surface (usually the role of upper cirrus clouds), therefore increasing the Earth's temperature. Others partially reflect sunlight back to space (usually the role of lower, warmer clouds), therefore increasing albedo and cooling the planet.

The goal of geoengineering is therefore creating these clouds. This procedure is known as 'marine cloud brightening' or 'cloud whitening'. How is this done? To understand this, we need to clarify something first. In order for clouds to be created, small particles called Cloud Condensation Nuclei (CCN) are needed, so that water vapour can condense around them. This is the origin of clouds.

Image showing the albedo of clouds, depending on their depth and drop concentration. Salter et al, 2008

Dust and general pollution works naturally as CCN over cities, and in all but in the thickest clouds, albedo is increased. As the majority of these clouds are not thick, the net result is a significant increase in cloud albedo (Twomey, 1977).

However, CCN over oceans is more scarse (Albrecht, 1989) and is the place where scientists consider geoengineering can be important. CCN could be increased by spraying sea water to the air, and therefore the tiny particles of salt could be used as nuclei. Therefore clouds would be formed with more and smaller droplets. Therefore, the surface area of these droplets increases and so does the reflectivity of the clouds. (Latham et al, 2008 ). Also, these particles would be small enough so as to prevent precipitation formation, therefore creating long lasting clouds (Albrecht, 1989).

Ship in charge of spraying sea water into the air. Source.

Trails left by ship spraying sea water to the air as photographed by NASA.

Implementation of this technique includes airplanes or ships, using wind as the main source of distribution of CCN. This is discussed in Salter et al, 2008.


Advantages:

• This technique uses existent technology (airplanes, ships) and natural resources (sea water), therefore it could be rapidly implemented. 
• Effects could be observed after one year of the implementation. 
• This process occurs naturally in the environment, in processes like ocean foam and others, so risk of catastrophes are not big. 
• If a negative side effect were to occur, the process can be stopped and effects would completely vanish within 10 days because of the continuous precipitation of the CCN. 
• Contamination is nonexistent given that it is sea water that is directly sprayed. 

Disadvantages:

• Effects are local, and therefore can produce unknown effect on water and air circulation. 
• Water vapour must be continuously sprayed because of precipitation. So the cost of this procedure can be high. 
• The termination of this technique conveys the same problem as the one discussed in the stratospheric aerosols. I.e, if the geoengineering is suddenly stopped, temperature will drastically increase to the value it would have had if geoengineering was never done. 

Stratospheric Injections

In the video we showed introducing geoengineering techniques we discussed one form of geoengineering that has not yet been studied in detail in this blog. This is the injection of some particular gases into the stratosphere.

The stratosphere is the layer just above the troposphere. Temperature in the troposphere decreases while you increase height. In the stratosphere is the other way round, and the limit between these two layers is defined as this inflection point. The good thing about the stratosphere is that there is no precipitation here, and therefore the particles injected into it will mainly be eliminated by gravitation onto the Earth. It is important to have in mind that global warming is leading to a warmer troposphere, and a cooler stratosphere.

Possible methods for the injection of SO2 into the stratosphere. These include airplanes, balloons, a tower or artillery. Source: Alan Robock.

The method consists on injecting directly SO2 into the upper stratosphere. How do we know the addition of SO2 into the stratosphere would have a cooling effect? Actually, because it has already happened a lot of times. Every time a large volcano erupts, large amounts of sulphur dioxide are released into the stratosphere and converted into sulphuric acid. These particles reflect sunlight back to space, and therefore produce a significant decrease in temperature in the lower stratosphere (and an increase in the stratosphere) in the following 2-3 years.  (Alan Robock)

The greatest evidence we have is the eruption of Mount Pinatubo, the largest one in the last century. Even though global temperature decreased, as was scientifically predicted, these changes were uneven. As Robock and Mao explained in 1992, these changes were mainly due to indirect changes in wind and North Atlantic Oscillation changes.

Change in temperature in the lower troposphere after the eruption of the Mount Pinatubo, 2001. Alan Robock, 2002

Several studies have been made to try to model what the results of these injections would be. Models show that global mean temperature could stay at pre-industrial levels, but, just as happened with the local effects in the eruption of Mount Pinatubo, these effects are not homogeneous (Schmidt et al., 2012). The SAT would be slightly colder in the low latitudes and hotter in the higher latitudes. According to the different models, temperature in the Arctic will suffer an increase from 0.8K to 1.8K.

Difference in surface air temperature between geoengineering model (G1) and pre-industrial levels (piControl).

The mean global precipitation will not remain the same as in pre-industrial times. It will decrease a value from 3.6% to 6.1%, depending on the model considered. This decrease is also not evenly distributed throughout the world.

Difference in precipitation between geoengineering model (G1) and pre-industrial levels (piControl).

However, these images don't take into account the predictions for temperature and rain variations for the future. This is why it is interesting to consider the following, studied by Matthews and Caldeira, 2007.

Images (a) and (b) show the projected SAT and precipitation according to the IPCC's A2 CO2 emissions scenario, without any geoengineering. Images (c) and (d) show the projection of the A2 scenario plus geoengineering.  

Advantages:
So, the effect of reducing the mean global temperature to pre-industrial levels seems really good at first sight. Also, this method is relatively cheap, and it has the great advantage of being quick (it would start acting after one year, Shepherd et al, 2009). This makes this method very interesting in terms of the possibility of needing to abruptly cool the global mean temperature.

Disadvantages:
The temperature change is not evenly distributed, and the precipitation will be significantly reduced. This will have severe consequences like droughts, food and water supplies issues or health issues. Also, stratospheric injections of SO2 lead to the destruction of ozone (Pitari et al, 2014), and changes in the North Atlantic Oscillation and winds are expected (Robock and Mao, 1992).
Another important negative aspect of this kind of geoengineering is the fact that, according to studies (Matthews et at, 2007), once you start doing it, you can never stop. Otherwise temperatures will increase just as if geoengineering had never been done. This slope would be higher that the natural process and therefore can be even worse than doing nothing because of adaptation complications for our society.

The effect in SAT under the A2 IPCC scenario (red) with no geoengineering, and the same emission scenario adding geoengineering at 2000 (blue), 2030 (green), 2050 (orange) and 2080 (purple). 

The effect in SAT under the A2 IPCC scenario (red) with no geoengineering, and the same emission scenario adding geoengineering at 2000 (blue), but stopping at 2030 (green), 2050 (orange) and 2080 (purple).  We can see how all these scenarios end up approaching the original A2 scenario.

In conclusion, we can think this method can be very interesting because of it's effectiveness and it's rapidity, but it is of extremely high risk, because of all the studied and also some yet unstudied possible side effects in biology of human life, for instance.

Increasing Surface Albedo: Crops and Deserts

Bio-geoengineering vegetation

Rather than inventing new technology, scientists are considering the possibility of bio-geoengineering. It is known that different plants have different albedos (absorb a different percentage of energy), mainly because of their difference in morphology, canopy form and other inner properties. Therefore, we could select the crops with higher albedo and therefore increase total albedo of the Earth. 

But this can only be done in a small percentage of land, where there is no water, no deserts, and no urban cities. As a consequence, this seems like it would be a tiny difference, so the basic question is, would it make any difference? 

Ridgwell et al, 2009, ran a model to find out the answer to this question. They assumed a CO2 concentration of 700 ppm and compared the modelled Surface Air Anomaly for 700 ppm with no crop modifications vs 700 ppm with crop modifications. 

The results are shown in the following image. We can see that this method can bring a decrease of more than 1ºC in some areas of North America and Eurasia in summertime (JJA). However, in winter (DJF), no significant changes can be observed in these regions, mainly because the percentage of snow reduces the impact on any vegetation change, and also because of the reduced energy income.

It is worth mentioning the significant decrease in temperature that would exist in the Barent Sea, possibly improving sea-ice retreat.

Surface Air Temperature anomaly for 700ppm CO2 concentration and biogeoengineering according to Ridgwell et al (2009)

Desert reflectors

Deserts seem to be the ideal candidates for albedo modification, because of their vast extent, because they are mainly inhabited and because they are relatively useless (Gaskill, 2004). However, deserts are currently the second area with highest albedo (after ice) with a value of 0.36. Therefore increasing the albedo would be difficult. 

Gaskill proposed covering 4.5 of the total amount of 7.5 million squared miles of desert with a reflective surface, to increase albedo. This would increase the desert mean albedo from 0.36 to 0.8, and lead to a total net radiative forcing of -2.75 W/m2. 

We can see this amount is much more significant than the amount discussed by increasing urban albedo, or even increasing crops albedo, and is very close to the -4 W/m2 we discussed we ideally needed. 

Now, this is my personal opinion. However great the figure of net radiative forcing is, it is clear that this solution is in the ethic borderline to what a lot of people criticise about geoengineering, because we are "playing God" with planet Earth. This is an example where things could perfectly get out of control. The addition of a man made material to 10% of the total planet surface could have infinite chaotic secondary effects, either ecological, climate or others. Air circulation and sand circulation play important roles in the climate of the entire world and we have to be cautious.

A very important movement against geoengineering that talks a lot about the option of increasing albedo in deserts and the problems it could bring.

Conclusion, this solution is considered to be very expensive (trillion dollars per year, Shepherd et al, 2009), and dangerous, but very efficient.

That was all for today! see you soon!

:)

Increasing Surface Albedo: Reflective roofs and pavements

The objective of SRM is to reduce radiative forcing of our planet or, in other words, increase the amount of radiation reflected by the Earth. Current mean albedo (this is, the proportion of energy reflected) is 0.15 (Shepherd et al, 2009). This means we are reflecting 15% of the incoming energy, and therefore absorbing 85% of it.

This percentage of absorbed energy has increased due to the increase of greenhouse gases (GHG) in the atmosphere. So clearly the best option would be cease the burning of fossil fuels and therefore stop increasing the effect of GHG. As we are still far from reaching this ideal solution, others have been considered.

To cool the planet, the proportion of energy reflected should increase from 15% to 17% (difference of -4 W/m2) (Shepherd et al, 2009). One could think, at first glance, this is not a very important increase, and it should be easy. But, when we think that the majority of the Earth's surface is covered by ocean, and oceans' albedo is the lowest (mean 10%), then changing this last 2% by only working on land becomes a much harder job.


So one of the options considered by scientists is the option of making our planet brighter. This can be made by

• Making white every rooftop and whitening urban places in general.
• Reflective crops
• Deserts reflectors
• Reforestation
• Ocean Albedo

We will discuss these options in this and further entries.

Increasing rooftop and pavement albedo

Everyone knows the colour white is the one with the highest reflectance power.  So, the first option discussed is using high reflectance paint (bright white paint) over roof tops and pavements in urban cities.
The questions are: Would this make a change? Does it have any side effects?

In urban cities, roof top area varies from 20% to 25%, and pavement area vary from 29% to 44%, (Akbari and Rose, 2008).  Several people (Akbari and Rose, 2008, Menon et al, 2010, Oleson et al, 2010) did the experiment to see which would be the change in albedo by painting roofs and pavements white, and the all reached similar conclusions. The result is an increase in albedo of between 25% and 15% in rooftops and pavements respectively, resulting in a 10% increase in global albedo of urban cities. This number drops to half this value when the paint is "light coloured" instead of white (Akbari and Rose, 2008).

Temperature estimation in ordinary circumstances, increased albedo of 0.05, and increased albedo of 0.1. (Akbari et al., 2012)

Starting to do this implies a political decision of forcing inhabitants to paint their roofs white. Cities like California did so in 2005. However, due to aesthetic reasons, this was adapted from "white roofs" to "light coloured roofs" in 2010, and it is not considered in a lot of places because of it.


HOWEVER, these are the temperature and albedo modifications for the urban city ONLY. What about the totality of the Earth? What net consequences would these modifications bring to the total albedo? the result is a net radiative forcing change of -0.01 - 0.2 W/m2. This is significantly small, mainly because of the small percentage of urban cities. If we compare to what we said we needed (-4 W/m2), we can see it is negligible on a global sense. However, locally, it seems to have very good results.

The question now is, does it have side effects??

Of course it does, plenty...

Positive side effects: 
Painting rooftops white reduce the electricity consumed in air conditioning. These reductions where calculated by Parker et al, 1995, to be between 10 and 45% in Florida, USA. Additionally, simulations in Los Angeles by Taha, 1996 predict smog reduction of 10-20%. All these reductions would bring as a consequence great monetary savings. The final benefit involves a greater useful life for materials (Akbari et al, 2001).

Negative side effects:
The colour white can create visual discomfort that could lead to eye-illness, or even traffic accidents. Also, some roof tops are not designed to be painted, such as tiles or other materials. High albedo tiles can be created but at greater cost. Additionally, maintenance must be regularly performed for the albedo to remain high, and this also adds up to the cost of the general procedure (Akbari et al, 2001).


All this painting and manteinance makes this procedure one of the "most expensive and least effective ones" Shepherd et al, 2009.




We will discuss other options in next articles. Hope you enjoyed this as much as I did!! :D