Get wind of this ....

Energy is an essential component of global socio-economic development and economic growth. The demands for energy are therefore not going to disappear at any point, in fact, they are likely to grow and as a result the viability of renewable energy methods in reducing the use of fossil fuels and ultimately reducing anthropogenic climate change is a key consideration.

Wind Energy is another form of solar energy whereby sunlight that hits the ocean, warms sections of the ocean causing the air to warm up and rise which, in turn, generates surface winds. It's potential to supply energy is large and subsequently it is one of the main renewable energy methods. It has also been one of the fastest growing energy technologies of the past decade (AWEA, 2002) and as the industry has grown, so has the size of individual wind turbines and the size of group developments. As wind is significantly affected by topography, weather conditions and land use patterns (Ramachandra and Shruthi, 2005), developers are beginning to look further offshore to harness maximum amounts of energy. In doing so, greater economies of scale will likely push the rating of individual wind turbines into the 3–5 MW range with maximum wind farm capacity potentially reaching 1000 MW (Milborrow, 2003). Wind farms of this scale have the potential to provide a sizeable percentage of local power demand and generation capacity, particularly when their output is fed into small or transmission constrained power grids.

Advantages 
Both onshore and offshore wind have the same benefits with regards to conventional power sources. Most notably, wind power has very low carbon emissions over its lifecycle and it has negligible emisssions of mercury, nitrous oxides and sulfur oxides. Another benefit of wind power is that it does not use fuel and is therefore freed from the price volatility associated with electricity generated from oil, natural gas, biomass, nuclear and coal (Snyder and Kaiser, 2009). Wind power does not rely on large sources of freshwater as conventional sources of power do (DOA, 2008).

In the near term, offshore wind power will be more expensive than onshore wind power, however, there are several benefits of offshore wind power that are not shared by onshore wind; these benefits may or may not justify the additional costs. These benefits include

• Offshore locations can be preferable to onshore locations - in the US, for example, offshore wind power is physically close to the major population centers of the coastal United States, thereby removing the need for expensive high voltage transmission (NREL, 2008)
• Offshore winds are also generally stronger and more constant than onshore winds. As a result, turbines can operate at their maximum capacity for a larger amount of time and the constancy of wind reduces wear on turbines and provides a more constant source of power reducing the need for backup sources (Snyder and Kaiser, 2009). Increases in wind speed can lead to a 150% increase in electricity production for offshore wind turbines and an increase in the capacity factor of the wind farm from about 25 to 40% (Junginger et al., 2004).
• Turbine noise is an oft-cited criticism made by opponents to onshore wind power (Pederson and Wey, 2004). The offshore wind power industry does not have to be as concerned about turbine noise as does the onshore industry.
• As a result, the offshore industry can also use far larger turbines. These larger turbines should make offshore wind power more economically attractive due to scale economies (Snyder and Keiser, 2009).

Disadvantages
One of the most substantive criticisms of wind power is that it is unable to provide constant, predictable power to the grid. Electricity grids are designed to send a constant electricity to consumers and as a result they rely on power plants to produce predictable and steady electricity. Wind energy is not steady and varies on the scale of minutes, hours, days and months and the changes in wind power output are difficult to predict ahead of time (Snyder and Keiser, 2009). As a result, integrating wind power into the electricity grid requires back up systems for when production on wind farm changes and is too low to produce electricity (Lund, 2005). This however increases the total national cost of electricity. The DOE has estimated that the supply up to 20% of the nation's electrical use from wind power would cost up to $5/MW h in integration costs.

Other disadvantages regard the aesthetics of wind farms and the noise that turbines make. In Denmark, Ladeenburg and Dubgaard (2007) examined the willingness of the population to pay to move turbines further from the shoreline. With an 8km baseline, to move turbines a further 12, 18 and 50km away, respondents were willing to pay 46, 96 and 122 Euros per year per household in order to move the farm farther afield.

While with regards to offshore wind turbines the risks and costs associated are assumed to be higher due to the offshore environment being significantly more uncertain and difficult than an onshore one. As such, the offshore environment would increase the maintenance of wind farms - which for onshore farms is quite low- as they would involve personnel traveling to and from offshore turbines; this increases equipment and time costs as well as insurance costs due to increased risks (Snyder and Keiser, 2009).

Could we count on Solar Energy?

After reviewed the various geo-engineering methods this blog is now going to review the option of renewable energy as a way to reduce fossil fuel combustion and ultimately climate change. First up is Solar Energy.

Solar Energy
Solar Photovoltaics (PVs) are arrays of cells containing that contain a material such as silicon that converts incoming solar radiation into electricity. Today, solar PVs are used in a number of applications from mediums scale utility level power generation to small scale residential roof top power generation (Trainer, 2013).  
Concentrated Solar Power (CSP) systems use mirrors or reflective lenses to focus sunlight on a fluid to heat it to a high temperature. The heated fluid flows from the collector to a heat engine where a portion of that heat is converted into electricity. Some CSP systems can store heat for a longer period of time so that electricity can be produced at night (Jacobson and Delucchi, 2011).

Distribution of solar energy at the Earth's surface (Jacobson, 2010)

The map above shows the average downward surface solar radiation at the Earth's surface. Globally, there would be 6500 TW of solar energy available from the world's land and ocean surfaces if all sunlight was used to power PVs; however, the deliverable solar power over land in locations where solar PV could practically be developed is about 340 TW.

CSP is estimated as being able to provide about 240 TW of the world's power output, which is less than PV as the land area required for CSP without storage is about one-third greater than is that for PV, however, the figure is still high. With thermal storage, however, the land area for CSP increases more as more solar collectors are needed to provide energy for storage, but energy output does not change and the energy can be used at night.

In cases where water-cooled CSP plants are being used the energy output may differ as plants can require water for cooling during operation (about 8 gal/kWh—much more than PVs and wind (∼0 gal/kWh), but the figure is still much less than nuclear and coal (∼40 gal/kWh) (Sovacool and Sovacool, 2009). Water-cooled plants therefore might be a constraint in some areas and air-cooled plants would have to be used. An advantage of this is that air-cooled CSP plants use >90% less water than water-cooled plants do, at the cost of only about 5% less electric power and with 2–9% higher electricity rates (USDOE, 2008b). As a result, air-cooled plants suggest a viable alternative to water-cooled plants for those constrained regions that may not have access to the water needed for cooling. 

Material Resources
Solar PVs use amorphous silicon, polycrystalline silicon, micro-crystalline silicon, cadmium telluride, copper indium selenide/sulfide, and other materials. As for the supply of material, the power production of silicon PV technologies is not limited by crystalline silicon however it is limited by reserves of silver which is used as an electrode (Feltrin and Freundlick, 2008) thus if silver as top electrode can be reduced in the future the supply of materials for solar PV systems will pose no problems for the development of a large global PV system.

Issues

One of the main issues facing the viability of solar (and wind) power today is whether these methods, that produce variable outputs, could provide reliable sources of electric power all day, every day, seasonally and yearly.  

An electricity system is therefore expected to be able to respond to changes in demand in a matter of seconds. Addressing this therefore, our current electricity system uses 'automatic generation control' (AGC) to respond to variations in the order of seconds to minutes, it used spinning reserves to respond to variations of minutes to an hour and peak power generation to respond to hourly variations (DeCarolis and Keith, 2005; Kempton and Tornic 2005). 

The main challenge facing the electricity system today is the daily and yearly variations in electric demand in comparison the the constant supply of nuclear, coal and geothermal energy. In addition to this, unexpected and extreme events can cause disruptions to plants - unplanned maintenance for example can shut down coal plants while extreme heat could cause nuclear plants to shut down. 

The down time of current electric technologies and systems is therefore important - in America coal plants on average were shut down for 6.5% of the year for unscheduled maintenance and for 6% of the year for scheduled maintenance (North American Electric Reliability Corporation, 2009). In comparison to this, solar prove more beneficial as they have an average down time of 1% although some projects have had no downtime, while others have had 10% (Banke, 2010). Moreover, when solar (and wind) project are down only a small portion of electrical production is affected, whereas when a plant is down a large fraction of the electricity grid feels the impacts - if a centralised plant is affected the WHOLE grid can be down! 

The main new issue facing solar (and wind) power is that the availability of energy at a single location varies and this variation does not match patterns of demand (North American Electric Reliability Corporation, 2009). As a result there are times when solar power systems can not meet demands and times when they exceed them and are left with a surplus of ultimately wasted energy. Having said that, there are other renewable technologies other than wind and power that do not vary as much. These other methods include tidal power, geothermal energy and hydroelectricity and will be the subject of my blog after solar and wind power have been discussed. In addition to this Delucchi and Jacobson (2010) put forward seven ways to design and operate renewable energy systems so that they can satisfy demands and minimise the production of energy that is not used. 

Playing with nature ...

The ability of plants to uptake CO2 from the atmosphere produced a focus on the potential of nature to geo-engineer the climate and mitigate future environmental change. The terrestrial biomass that have been examined specifically for geo-enigineering purposes are afforestation, reforestation and biochar.

Reforestation: refers to the establishment of forest on land that had recent tree cover
Afforestation: refers to land that hasn't had tree cover or forest for a longer period of time

Anthropogenic deforestation has been recognised as a major contributor to global warming both due to the loss of future CO2 uptake and the release of sequestered CO2 that occurs when trees are cut down. Afforestation and reforestation processes are considered to be cheap and safe techniques, that ultimately achieve the end goal of CO2 uptake from the atmosphere. Globally deforestation is decreasing and reforestation and afforestation are increasing in some regions (see fig 1). Despite this, the impacts of deforestation remain, with large losses having taken place in tropical regions (FAO, 2013).

Effectiveness
Candall and Raupach (2008) state that reforestation has the potential to reduce atmospheric CO2 by 70-100ppm by 2100. This high figure offers promise, particularly when compared to the predicted reduction of 130ppm that would be caused by ocean iron fertilisation (discussed in my previous blog post). Unfortunately, a close inspection of the methods of the paper reveals this figure is deceiving as it assumes that complete reforestation is possible when actually it is not. Moreover, a reduction of 70-100ppm by 2100, be as it may a reduction of atmospheric CO2, is not a large enough reduction to reverse the effects of anthopogenic climate change.

Impacts
It has been demonstrated that only 9% of land surface would be biophysically suitable for reforestation and afforestation. However, more than half of this available land is used for agriculture and as a result not only food security would be compromised, there would be a high socioeconomic cost to afforestation and reforestation as farmers would lose labour as their are replaced by low labour forestry management (Zomer et al., 2008).

Afforestation and reforestation processes could also have hydrological impacts as runoff would be reduced and 'green vapour' flows would increase. In 2008 Trabucco et al., concluded that afforestation on 27% of suitable land would be affected by a 80-100% decrease in runoff, while 50% of suitable land could experience a reduction of 60%. In particular decreases were prevalent in drier, semi arid areas and in conversions from grasslands to subsistence agriculture. Consequently, reforestation and afforestation could potentially effect water resources and water management which is particularly significant given rising concerns over water scarcity. Moreover, the characteristics of suitable land also need to be considered as many areas deemed as suitable land may exhibit problems i.e. the human activities prior to and the mode of establishment for new trees.

Decreases in runoff in areas that are deemed suitable for reforestation and afforestation 

Increases in green vapour flows in areas deemed suitable for afforestation and reforestation 

A key factor that is overlooked in research on reforestation and afforestation is whether the processes are likely to be adopted. A study by Schirmer and Bull (2013) examined this in Australia and showed that widespread adoption requires designing afforestation so it (i) provides a range of socio-economic benefits that go beyond provision of income; (ii) minimises disruption to land management flexibility; and (iii) is compatible with landholder beliefs about appropriate use of agricultural land. 

Further to this, economic markets are also an important aspect to consider. In 2012, during the recovery from economic downturn, the market for industrial roundwood and sawnwood production increased by 6%, while wood panel production increased by 2% compared to 2011 in North America. The Asia-Pacific also increased its prominance as a producer and consumer of forest products, with China taking the lead. Sawnwood production in the region climbed by 11 percent and panels by 6 percent compared to 2011.

The importance of considering the range of perceptions of stakeholders involved in both the implementation of methods and also in the wider market is thus highlighted. Perhaps more significant is the suggestion that without changing perceptions towards a realization of the danger of deforestation and the benefits and ultimately adoption of reforestation and afforestation, research of the effectiveness of the methods is a futile task. Thus, if the method is adopted in the future to combat climate change then efforts to change perceptions will also be needed. 

A sea of uncertainty

In 1999 when John Martin infamously asserted 'Give me half a tanker of Iron and I will give you an ice age' the world, perhaps, thought for a second that the problem of ocean acidification could be solved.

Phytoplankton absorb CO2 and sunlight to produce
energy and photosynthesis

His statement was made in response to his hypothesis that an increase in the primary production of planktonic communities found in high nutrient, low chlorophyll (HNLC) areas of the surface ocean would increase the amount of carbon sequestration from the atmosphere. This hypothesis arises as during the glacial period the interactions between iron availability and silicon usage by diatoms in the Southern Ocean are thought to explain, in part, the reduction in atmospheric CO2 concentrations (Siegenthaler, 2005). Iron rich conditions are therefore thought to have caused the long term sequestration of atmospheric CO2 that occurred during the glacial intervals.

Primary productivity in 30–40% of the world's oceans is limited by the availability of iron, particularly in the open-ocean regions of the Southern Ocean, equatorial Pacific Ocean and north Pacific Ocean (Moore et al., 2002). Increasing the amount of iron in these regions has thus been explored due to the potential of added iron to reproduce the interactions that occurred in the oceans during glacial period. 

Phytoplankton are nutrient limited and as a result an increase in the nutrients iron (Fe), nitrogen (N) or phosphorus (P), would increase their primary production, producing large 'blooms' of photosynthesising algae. The hope of studies that research iron fertilisation is that the ocean, with added iron, will sequester CO2 and thus slow the rising levels of warming caused by climate change (Armbrust, 2009) however most studies so far have shown increased productivity (see fig above) however this is limited to consumption and recycling in the surface - there is little deep water sequestration. 

Studies have focused on the use of iron due it being both the most efficient out of the three by 2 and 5 orders of magnitude (respectively) and the cheapest out of the three (The Royal Geographical Society, 2009).

Green patches in the sea are phytoplankton communities 

The IPCC have predicted that by 2100, mean surface ocean pH will be at a level of 0.44 units lower than pre-industrial levels while atmospheric CO2 will measure 965ppm (IPCC, 2000). Using these predictions, Cao and Caldeira (2010) measure the extent to which iron fertilisation could be used to reverse the effects of climate change by bringing us back to pre-industrial temperatures - or as John Martin asserts give us 'an ice age'. Their study found that iron fertilization could only reduce mean surface ocean pH to 0.38 units lower than pre-industrial levels while atmospheric concentrations of CO2 could only be reduced to 833ppm (Cao and Caldeira, 2010). 

Focusing more specifically on the Southern ocean, Zarharlev et al., (2008) concluded that even if there was continuous fertilisation, the uptake of CO2 would only reach a maximum of 1Gt - which is less than 11% of our annual emissions. More recently, Martin et al., (2013) have shown that iron fertilization enhanced net community production but not downward particle flux in the Southern Ocean due to the ability of zooplankton communities to reprocess sinking particles and alter particle size distribution - both of which prevent the export and sequestration of CO2.

Iron fertilisation is therefore limited as a method to address climate change as it can not bring about large scale reductions in surface ocean pH or atmospheric CO2. Further to this, it does not necessarily stimulate the particulate organic carbon (POC) export and sequestration desired under limited Si concentrations. 

In addition to this, there are a number of potential environmental impacts that could result from such large scale fertilisation such as - 

1. Ocean oxygen depletion - anoxia, caused by eutrophication in lakes and coastal regions, can have huge negative impacts on bethnic communities and thus the whole food web of the ocean and as oxygen depletion is an outcome of iron fertilisation the risk of anoxia is high, particularly in the Indian Ocean - the implication of this could be catastrophic. 
2. Nutrient depletion in surrounding waters 
3. Harmful algae blooms could develop
4. The size of the phytoplankton species may change and become larger which would have implications for the food web of the ocean
5. Increased greenhouse gases as a result of increased methanogenesis that occurs in the digestion of phytoplankton

According to the IPCC, ocean iron fertilisation offers a potential method for removing CO2 from the atmosphere due to the potential of phytoplankton to sequester carbon dioxide in the form of particulate organic carbon. Having said that, they also state that ocean iron fertilisation remains largely speculative and many of the environmental side effects need to be assessed. Large scale iron fertilisation could have negative impacts on marine life and human health.

Despite this, however, there are rumblings that a commercialisation of iron fertilisation will occur in order to sell carbon offsets in a future where the price of carbon has increased due to climate treaties having mandated even stricter caps on emissions and governments having issued higher taxes.

As iron fertilisation would likely occur beyond a countries 200 mile exclusive economic zone, regulation would fall under international law. At present, the London Convention treaty that concerns the sea promotes the effective control of all sources of marine pollution and governs the deliberate disposal of waste or other matter at sea for its 82 treaty members. The updated London Protocol agreement specifies that all dumping is prohibited except for some specified wastes such as carbon dioxide from industrial carbon capture processes into sub-seabed geology. Under these two agreements iron fertilisation is not specifically dumping however even if it were it is not unusual for entities seeking to skirt a treaty to register their ships in a nation that is not part of the treaty or does not enforce is very strictly (Powell, 2008).

These weaknesses in International law may be countered by economic markets and the strict regulations imposed on the trading of carbon credits by the Kyoto Protocol and the European Union Emissions Trading Scheme. In an attempt to console, Powell (2008) highlights these regulations mean that carbon credits from iron fertilisation can, at present, only be sold on the voluntary carbon market. 

In my opinion, this isn't consoling at all as, despite it currently being much smaller than other segments of the carbon market, the voluntary market is growing and in addition to this it is not regulated strictly like Kyoto and EU projects - this could be dangerous as improper and inaccurate accounting and dumping of iron could occur. Buesseler et al., (2008) argue that it would be premature to start selling carbon offsets from commercial iron fertilization due to uncertainty over how effectively CO2 is removed from the atmosphere and retained in the ocean for a significant amount of time. In addition to this there are numerous environmental impacts and risks of unregulated dumping.

Buesseler et al., (2008) later wrote "moving forward on OIF should only be done if society is willing to acknowledge explicitly that it will result in alteration of ocean ecosystems and that some of the consequences may be unforeseen". In my opinion I am not sure if gaining societies acknowledgement is enough to permit iron fertilisation (is acknowledgement approval?), nor do I feel that societal acknowledgement is the direction that should be taken 'moving forward'. If the method is ineffective and the risks are too great than the method cannot be used to fix climate change.

Lets take a News Break ....

'Reducing sunlight unlikely to cool earth' 

Listed above is the title of an article published on 7th December by the Climate News Network which asserts that geo-engineering whereby, the planets thermostat is controlled by blocking, absorbing or reflecting some of the sunlight hitting the Earth, would not work to fix climate change. 

This conclusion is made in response to two recently published papers that both arrive at the same result - that you cannot fix climate change by reducing solar radiation due to the effects this would have on rainfall patterns. The first paper to make this conclusion was published by a US led group of scientists while the more recent paper was published by Axel Kleidon and Maik Renner of the Plank Institute for Biogeochemistry in Jena, Germany. 

The papers arrive at this assertion by highlighting the different responses of sunlight and surface warming on the hydrologic cycle and on vertical transport within the atmosphere. As such SRM geo-engineering that compensates for 2 degrees of warming causes the water cycle to weaken by 2% and vertical transport by almost 8%. 

This research on SRM leaves me particularly skeptical about the viability of the various methods I have discussed thus far in this blog, particularly as much of the research on the various methods puts forward impacts upon precepitation as a possible side effect. Thus it is with skepticism that I embark on the second part of my geo-engineering journey which looks at the various Carbon Dioxide Removal techniques that have been proposed as a solution to fix climate change.  

The last SRM Method …. Spaced Based

The idea of putting sunshades in space was first proposed by James Early in 1989 and since then the idea has been developed and proposed as a solution to climate change.

Space Based SRM would work to reduce the amount of solar energy entering the Earth by placing reflective materials such as dust particles or discs into orbit around the earth. The effectiveness of space based SRM is pretty much indisputable and unlike other SRM methods there is no physical limit of the extent of solar radiation reduction.

Issues arise when the logistics of space based SRM methods are taken into consideration as both the costs and magnitude of the methods are very high.

Image 1

The first proposal by James Early mentioned above consisted of one single sun shield situated at the Sun Earth Lagrangrian point 1 (See image 1). The shield would measure 2000km in width and be 10μ thick in order to block 2% of the Sun’s solar radiation. The cost of implementing this method is between $1-10 trillion – not only is this range huge and therefore vague, the minimum cost of $1 trillion dollars is also huge and as a result other methods are likely to be considered over a space based shield. Moreover, the method becomes less feasible when the amount of work that would be needed to construct the shield in space is factored into the equation alongside the very high costs.

Addressing this issue is the developments of sunshields that are smaller in size but reflect the same amount of solar radiation (McInnes, 2010)– these highly engineered refractors are however significantly more expensive to produce thus although the magnitude of the space mirror may be reduced the costs would be even higher.

Alternatively and probably a more likely scenario would be the use of a large number of smaller sized discs with the same total surface area as that of one single disc (McInnes, 2010). The smaller sized discs could be free flying independent elements or they could form a large occulting disc (see image 2 below). An absorbing occulter uses lunar or near Earth asteroid material and the total occulting area grows over a period of 50-100 years to match the required reductions in solar insolation as carbon emissions rise.

Image 2 - Occulting Disc 

Roger Angel’s (2006) research proposes a cloud of free flying spacecraft, 100,000km in length, that consists of transparent material that deflects the path of radiation in order to reduce the suns heat by 1.8%. A total of 20million sunshades and launches would be required at the again very high cost of $600 billion.  In addition to this a further $30 billion would be required to build a launcher and $150 billion would be needed to cover the energy costs to use it.

Although space based methods are located outside the Earth, there are still environmental effects caused as a result of the methods. Lunt et al.’s (2008) study shows that the SRM world would be significantly different to a pre industrial world in a number of ways. Firstly Arctic sea ice would be lower, the ENSO would have a reduced amplification, the Atlantic Ocean overturning would be stronger and the hydrological cycle’s intensity would be less intense, most notably in the tropics. Such changes could have significant repercussions, ecologically and on societies, however these changes would be less catastrophic than those that would occur from global warming left unaddressed

Marine Cloud Brightening

SRM: Marine Cloud Brightening

Marine Cloud Brightening (MCB) is the process wherein the concentration of cloud micro-droplets in marine cloud systems is increased to give them a whiter appearance, which ultimately increases the amount of solar radiation they reflect.

How? ….

To increase the concentration of micro droplets, cloud condensing nuclei particles would need to be increased. Proposed methods have suggested using sea salt - a naturally occurring and very abundant form of CCN.

Difficulties in the method arise over implementation. How could sea salt be injected into the troposphere and be evenly distributed? Aircrafts and ocean vessels have been put forward as possible solutions to this problem. Due to the short residence time of less than 10 days, 1500 ocean vessels with 28 billion nozzles distributing more than 50 cubic meters of sea-water droplets per second would  be required to counteract a doubling of atmospheric CO2.

Image 1: The first Flettner Rotor used instead of a sail on the Battner-Battner ship which crossed the Atlantic 

Image 2: A conceptual image of a Flettner Spray Vessel 

This calculation would seemingly lead one to eliminate MCB as a solution to fix climate change however the work of Salteret al., 2008 seeks to address this issue as it proposes the use of ‘Flettner Rotor Ships’ rather than ocean vessels or planes (see Image 1). These ships are wind powered, remote controlled, unmanned, can be moved seasonally and most importantly spray sea water droplets into the troposphere. The ships are thus a low carbon and much more inexpensive method than vessel ships or planes. Moreover as sea water is also inexpensive the method as a whole has a suggested cost of £2 billion (Salter et al., 2008). Depending on maintenance costs, this method could be very cost-effective in the long term, particularly in comparison to the much higher costs of SRM methods.

Image 3: A sea going yacht conversion by John Marples
that has incorporated Flettner Rotors

The feasibility of Flettner Rotor Ships proposal is limited as the technology needed to withdraw sea water and effectively seed the troposphere is incomplete and thus effective implementation is not yet possible. This is not to say the method would not work, but until the technology is available the overall feasibility of the ships is unknown. Further to this, MCB is limited as it can only counter warming from doubling of CO2 –any warming beyond this could not be countered by MCB. The method is therefore restricted as it is unable to return us to pre-industrial temperatures however it should not be ruled out entirely as it could be used to stabilize temperatures and keep them below critical thresholds.

In terms of its environmental impacts of MCB on the whole, various models (Latham et al., 2008; Jones et al., 2010; Rasch et al., 2009) have suggested that albedo enhancement will be enough to balance the radiative forcing for a doubling of CO2 and in some cases the temperature reductions have been asserted to also be enough to reduce polar ice loss (Parkes et al., 2012).  MCB also has the ability to target specific areas meaning those areas most at risk to warming can be addressed. Parkes et al., (2012) demonstrate this through their models which show cloud modification in the Northern Atlantic reducing summer ice retreats. Although the links between climate change and extreme weather are still being explored (for more info have a look at Joon's informative blog) it has been asserted that increased sea surface temperatures might be linked to hurricane intensification. MCB, due to its capacity to be applied regionally, could therefore be used in hurricane prone areas to counteract them occurring.

Geo-engineering wouldn’t be the same if it had no negative effects …. Thus as for the negative environmental effects of geo-engineering, firstly there are the localized changes in albedo. Although these local changes were just stated as an advantage they can also be a disadvantage – the weather systems and climate of the earth are non-linear and so predictions of the impacts upon regional climates and the global climate system itself are unfortunately shrouded with uncertainty and so a negative response to MCB cannot be entirely rule out. The non-linear nature of the planet also makes the link between MCB and polar ice reductions (Parkes et al.,2012) precarious as relations or more specifically responses are unlikely to be this in sync and predictable – particularly when current modeling and knowledge limitations about climatic responses and relationships are taken into account. Finally, MCB has been shown to cause changes to both the magnitude and pattern of precipitation. Having said that, a study by Jones and Haywood (2012) that uses the HadGEM2–ES model has shown that impacts on precipitation are less in degree to that simulated by previous studies which use much simpler treatments of this geo-engineering process. This finding is important as it highlights the need for more knowledge and research on the climate intricacies that are related to this methods implementation.

Marine Cloud Brightening, like all the geo-engineering techniques discussed thus far, has positives and negatives as a method. It is limited in that we do not know how applicable the method is due to a lack of knowledge about climate intricacies. Furthermore, if warming surpasses a doubling of CO2 the method cannot be used to bring us back to pre-industrial levels of warming and when current rates of warming are taken into consideration the method is unlikely to be able to fully rectify climate change. More research is thus needed to understand the effects of the method and after this it’s application can be determined. However, if the choice had to be made between sulfate aerosols and MCB, sulfate aerosols have been argued as being the better option (Jones et al., 2011). In my opinion therefore I think researchers should focus on developing sulfate aerosol methods rather than both.

A note on stratospheric aerosols, the cryosphere and future climate change....

Stratospheric sulfate aerosols, the cryosphere and climate change …

Recently in my search for literature on stratospheric sulfate aerosols, I came across a few pieces on stratospheric aerosols and the cryosphere and as a recent lecture highlighted the importance of the cryosphere and the seriousness of the changes that are taking place within it I thought I would include a post about the viability of stratospheric aerosol injections in alleviating the loss of ice and sea level rise.

Changes in the crysophere such as the loss of Arctic sea ice and the Greenland and Antarctic ice sheets in recent years have been more rapid than expected. Global warming effects are projected to be the largest in the polar regions, however, it is these regions where climatic responses to warming are most uncertain. The potential impacts of further changes have consequently raised the question of whether geo-engineering, or more specifically, stratospheric sulfate aerosols, can be used to alleviate the loss of ice and sea level rise.

Using the Community Climate System Model version 3, Bitz et al., (2010) imposed stratospheric sulfate aerosol loadings in a series of integrations with the model and found that aerosols can counter ‘many effects of greenhouse warming’ however perfect cancellation is not possible. Rather, when aerosols roughly cancel global average warming, temperature changes in the polar regions are still 20-50% of the changes in the warmed world (McCusker et al., 2011). The aerosols cause a southerly migration of the southern hemisphere jet (McCusker et al., 2011) and these atmospheric circulation changes cause the over-cooling in Arctic summers and residual warming during Arctic winters (McCusker et al., 2010).

The conclusion that arises is that aerosol geo-engineering can serve to counter some of the climate impacts of stratospheric ozone recovery and rising CO2 but not all. Having said that, projected responses to geo-engineering in polar regions have high levels of uncertainty due to the high levels of uncertainty that are present in projections for the polar regions in general. Consequently, the question of whether we can avoid polar climate emergencies is not certain. More robust depictions of a climate that has been geo-engineered are thus needed – a conclusion of more research being needed is yet again the case.