Technology-Based Geo-Engineering Options for the Mitigation of Anthropogenic Climate Change Due to GHGs Emissions.

The use of non-renewable resources such as oil and gas has been linked to global warming. Most of the non-renewable energy resources emit greenhouse gases into the atmosphere. A result of global warming the world continues to faces a number of major and unprecedented global environmental problems (Princiotta, 2011; Schaltegger, Csutora, & Huisingh 2011). Some of the effects of global warming include the rise of sea levels (Moore, Jevrejeva &, Grinsted 2011); drought (Strauss, Moltchanova, & Schmid, 2013); degradation of permafrost (Gao, Schlosser, Sokolov, Anthony, Zhuang, & Kicklighter2013), and increased risk of hurricanes and tornadoes (Mannshardt & Gilleland, 2013). The increase in greenhouse gases concentrations is according to the Intergovernmental Panel on Climate Change (IPCC) linked to human activities such as burning fossil fuel, which eventually result in global warming. This is supported by the Fifth Assessment Report (AR5) of 2013 which showed that carbon dioxide (CO2) concentration in the atmosphere has over the years increased rapidly (IPCC AR5, 2013). Thus, aggressive greenhouse mitigation measures could play an integral role in mitigating the effects of anthropogenic climate changes.

The purpose of this paper is to compare and contrast technology-based Geo-Engineering options for the mitigation of anthropogenic climate change due to greenhouse gas emissions. The paper includes a discussion of technical feasibility, likely economic costs, and any risks of unintended outcomes associated with technology-based Geo-Engineering options for the mitigation of anthropogenic climate change.

Statement of Scope & Objectives of study

Anthropogenic climate change according to Braun (2016) refers to the production of greenhouse gases (GHG) as a result of human activities. Since the mid-18th century (the onset of industrialization), the amount of GHG in the Earth’s atmosphere has continued to increase steadily. Fossil fuels, including coal and oil as well as natural gas have been the primary contributors of the emissions and account for the vast majority of human-related GHG emissions (Schilling & Chiang, 2011). The GHGs, when trapped and combined with additional heat, gradually increase the average global temperatures, resulting in global warming. The IPCC has estimated that the absence of adequate climate policies in the world will result in the increase of the average global temperature by 1.4°C to 5.8°C (IPCC 2014). The long-term effects of an increase in global temperatures include rise in sea levels, heavy precipitation events, longer droughts, and hurricanes (IPCC 2012).

CO2 emitted is the most substantial of the anthropogenic greenhouse gases related to global warming. In addition, the large amounts of CO2 result from the use of fossil fuels which are non-renewable resources. It has reached a point whereby anthropogenic climate change has become one of the most important issues that must be addressed in the 21st century. This is necessary to solve impacts of climate change such as the unprecedented European heat waves and the increases in hurricane intensity.

Addressing this issue requires both adaptation and mitigation, and particularly geo-engineering. The scope of this paper is on geo-engineering as the solution of last resort to mitigation of anthropogenic GHGs to reduce global warming effect. In regard to mitigation, the focus is to decrease the short-term rate of change as well as the long-term temperature realised. Technology based geoengineering is composed of a set of novel methods for climate change management. However, it poses new challenges related to ethics, global governance, risk assessments, human–nature relationships, and public deliberation. The use of geoengineering methods has the theoretical potential to allow humanity to adjust global climate and its impacts according to its desires. Nonetheless, the cost and risks to be incurred are relatively enormous in terms of political conflict, environmental risk, and possibly irreversible unintended consequences. Accordingly, geoengineering techniques evoke both hopes and fears to mitigate anthropogenic climate change as a result of GHGs.

The objectives are:

To compare and contrast the available technology-based geo-engineering options for the mitigation of anthropogenic climate change.
To discuss technical feasibility of the technology-based geo-engineering options.
To establish the likely economic costs and any risks of unintended consequences from the use of technology-based geo-engineering options to mitigate anthropogenic climate change.

LITERATURE REVIEW

Global warming has resulted from the actions of humans, and it has disastrous consequences as well as costly detrimental effects (Zhang et al., 2014). Mitigation and adaptation strategies have not been effective or sufficient in reducing the effects of anthropogenic climate change. The Mauna Loa Observatory in Hawaii noted that in 2013, the CO2 concentration present in the Earth's atmosphere officially exceeded 400 ppm, compared to 320 ppm in 1958 (Ming et al., 2014). The IPCC's 2007 assessment recommended that it was imperative to keep atmospheric GHGS below 450 ppm with the intent of keeping the temperature rise below the 2 degrees Celsius target (Ming et al., 2014). There are many scenarios that have been considered to reduce GHG emissions slowly to maintain the average temperature rise. Nonetheless, agreements are needed between the biggest polluters, which can be achieved via an international agreement. Human GHG emissions result from the exploitation of non-renewable resources such as oil and natural gas (Schilling & Chiang, 2011).

The Concept of Geo-Engineering

The term ‘geoengineering’ refers to a number of approaches that use large-scale technologies with the aim of slowing down and/or reversing the impacts of anthropogenic climate change (Corner, Parkhill, & Pidgeon, 2010). Thus, it is composed of a diverse combination of technologies that can be used to mitigate the effects of climate change as a result of human behaviour. Anshelm and Hansson (2014) have described geoengineering as “the deliberate manipulation of the global climate using grand-scale technologies that poses new challenges in terms of environmental risks and human-nature relationships” (p. 101). The association between these geoengineering’ technologies is the ability to deploy them to control as well as alter the earth’s climate. Ming, de_Richter, Liu, and Caillo (2014) pointed out that “Geoengineering aims at stabilising the global climate, reducing global warming, and fighting anthropogenic climate change owing to two strategies: shortwave (0.3–3 μm) sunlight reflection methods and carbon dioxide removal technologies” (p. 794). Thus, technology-based approaches to the mitigation of anthropogenic climate change have remained the last resort. This is because reduction methods have so far been ineffective.

Geo-Engineering Options

According to Corner et al. (2010), “geoengineering technologies fall into two categories: proposals to remove a proportion of carbon dioxide from the atmosphere (carbon dioxide removal, or CDR) and proposals to reflect a proportion of sunlight away from the earth, thereby lowering global temperatures (Solar Radiation Management – SRM)” (p. 5). Thus, geoengineering methods are based on their ability to remove CO2 from the atmosphere and their ability to manage radioactive forces to mitigate the environmental effects of anthropogenic climate change.

The CDR approaches are applied to handle the primary problem of climate change, which is CO2. Thus, CDR entails the removal of CO2 from the atmosphere. The process is slow and typically needs a long duration to have visible effects on the climate system (Corner et al., 2010). Conversely, SRM is an approach that entails compensation for GHG-induced warming through a reduction of the incidence as well as the absorption of solar radiation. The effectiveness of SRM is realized via a wide range of approaches, including enhancing surface albedo and enhancing atmospheric albedo (Shepherd, 2009). The rationale for using space-based methods is to avert incoming solar radiation before it reaches the Earth's surface. The SRM, compared to the CDR, could reduce radiative forcing rapidly and thus be used as the last resort for mitigation in order to deal with the adverse impacts associated with anthropogenic-driven climate change (Sánchez & McInnes, 2015).

The CDR methods, compared to SRM approaches, are the least risky methods. This is because CDR schemes entail approaches such as large-scale afforestation and reforestation, CO2 capture and storage, biochar production, ocean fertilisation, and chemical weathering, among others. Nonetheless, CDR schemes only sequester atmospheric CO2, which is significantly small in comparison to the cumulative anthropogenic emissions. This makes it less effective in preventing the mean surface temperature from increasing (Keller, Feng, & Oschlies, 2014). The SRM approach is applied to make adjustments to the amount of sunlight that is able to reach the Earth’s surface so as to balance long-wave greenhouse gas forcing. According to Zhang et al. (2014), “main SRM schemes include injecting sulfur into the stratosphere to block incoming sunlight, putting sun-shields or dust clouds in space to reflect sunlight, and injecting sea salt into the air above the oceans to increase the reflectivity of clouds” (p. 2). Niemeier, Schmidt, Alterskjær, & Kristjansson (2013) pointed out that all these SRM schemes have cooling effects, but with differing effects on precipitation. Typically, SRM approach when applied has the capability to significantly decrease solar radiation absorbed by the earth and lower global temperatures rapidly (Royal Society, 2009; Lenton & Vaughan, 2009). In comparison to CDR, SRM is believed to have the largest potential for mitigating warming, in spite of the potential for large side effects (Keller et al., 2014; Lenton & Vaughan, 2013).

SRM measures are technology-based, where sunlight is reflected to reduce global warming without reducing the concentration levels of CO2 in the Earth’s atmosphere. The commonly used SRM options include orbiting space mirrors, injecting aerosols into the stratosphere, painting roofs white, or creating artificial clouds from seawater (Keller et al., 2014). Conversely, CDR options address the amount and concentration of CO2 in the atmosphere with the aim of reducing the concentration. The common CDR options include the use of air capture technologies or CO2 sequestration.

According to a report by the UNEP (2012), there is no single geoengineering approach that presently meets all three basic conditions for safety, effectiveness, and affordability. All the technology-based geoengineering is in its development stages and is mostly theoretical and not tested in terms of its effectiveness on a large scale, especially when applied to capture or mitigate the atmospheric stock of CO2.

Differences Between CDR and SRM

The primary difference between SRM and CDR, according to the Royal Society (2009), is that carbon sequestration is applied to address the root issue, while solar reflection is applied to solve the symptom, which is global warming. In addition, the problems that arise are that the reflection approach does not consider the acidification effects of oceans resulting from excess CO2 in the Earth’s atmosphere absorbed by the sea (Royal Society, 2009). In addition, the approach that applies the injection of particles into the atmosphere could alter rainfall distribution and cause a reduction in the global quantity of rainfall. Also, the reflection techniques require constant replenishment over their lifetime, which makes them costly to use because they are not economically feasible.

The other difference linked to SRM techniques is that they could substantially influence the climate within a short period of time, compared with CDR, which takes a long- time to have results (Royal Society, 2009). Thus, there is greater uncertainty related to net climatic effects as a result of using SRM methods. Technically, SRM could be deployed at low cost, but SRM may unevenly ameliorate climatic change and culminate in serious unintended consequences (Zhang et al., 2014). For instance, SRM could, in some instances, produce droughts that have severe implications for regional and global food production. They could also delay the recovery process of the ozone layer because SRM does not address ocean acidification. On the other hand, “under CDR, the decrease in atmospheric CO2 would reduce ocean acidification except in cases where the ocean is used directly for carbon sequestration” (Jones et al., 2013, p. 22).

Impacts of Geoengineering

There are economic costs and risks of unintended consequences from the use of technology-based geo-engineering options to mitigate anthropogenic climate change. The table below summarises impacts of CDR techniques in geo-engineering as provided by UNEP (2012).

Table 1: CDR techniques and Summary of Potential Impacts

The aim of the CDR is to remove the amount of CO2 that is the primary causal agent of anthropogenic climate change and ameliorate ocean acidification. From the table, the possible impacts include ocean acidification, effects on sea ecosystems, habitat destruction, effects on soil structure, and potential leakage of CO2 into the earth’s surface. The CDR methods compared to SMR are more effective and feasible, as they have less effect on the environment and are economically and technically feasible (UNEP, 2012).

Different international treaties might limit the use of some of the technology-based geoengineering experiments in the real world because of their potential risks and effects on humans and the environment (Kintisch, 2007; Royal Society, 2011). Also, Zhang et al. (2014) contended that technical risks and uncertainties linked to geoengineering climate are numerous. In addition, the benefits and costs of technology-based geoengineering vary spatially over the globe, and as such, some could be applicable in some countries and regions while others could be faced with the worst of circumstances (Bala & Nag, 2012; Haywood, Jones, Bellouin, & Stephenson, 2013; Xia et al., 2014). Experiments conducted under the Geoengineering Model Intercomparison Project (GeoMIP) have established that most of the SRM geoengineering schemes compared to CDR have the capability to reduce temperature anomalies rapidly resulting from GHGs (Kravtiz et al., 2011; Kravtiz et al., 2013).

On the other hand, the unintended impacts of SRM techniques include implications for ocean and land ecosystems. In addition, “SRM techniques that involve increased sulphate aerosols in the stratosphere will enhance ozone depletion, particularly in polar regions” (Jones et al., 2014, p. 23). Other impacts that have been associated with atmospheric-based SRM techniques include an increase in the proportion of diffuse light, a reduction in the total irradiance that reaches both the land and ocean surface, and a decrease the proportion of direct light.

SRM-induced changes result in environmental effects that affect both light quality and quantity. For example, diffuse light could be effective in canopy penetration, whereas atmospheric SRM could result in an increase in the net increase in terrestrial primary production (Mercado et al., 2009). Enhanced cloudiness/cloud brightening and aerosol-induced ‘global dimming’ have different effects on terrestrial carbon sequestration, and this could result in differences in terms of the outcomes in terms of global warming mitigation (Alton, 2008).

DISCUSSION AND EVALUATION OF EVIDENCE

Technology-based geoengineering is made up of CDR and SRM options that can be applied to mitigate the changes in climate change following continued global warming. The exploitation of natural energy resources such as oil and coal continues to add extra CO2 to the earth’s atmosphere. Reduction methods are no longer effective and sufficient, and as a result, technology-based geoengineering options are proposed as effective.

The Two Classes of Geoengineering Methods

The study has established that geoengineering is composed of CDR and SRM methods of mitigating anthropogenic climate change. As pointed out in the literature review, CDR methods are based on the control of CO2 concentration and stock present in the Earth's atmosphere. The approach is based on the supposition that a reduction in CO2 could result in reduced GHGs in the long term (Ming et al., 2014). The CDR options are applied to remove CO2 from the atmosphere. Although the process is slow, the effects are commendable in the long term (Corner et al., 2010). Thus, the CDR methods augment efforts to minimize emissions immediately, but the options could take several decades before they could have a discernible effect on climate. The deployment of CDR for CO2 removal on a global scale would essentially result in emissions reduction and lower concentrations within a period of centuries instead of millennia (Royal Society, 2009).

SRM methods, on the other hand, operate on the radiative fluxes, which are part of the Earth’s energy balance. SRM is used to enhance compensation for GHG-induced warming via reductions and is applied because of its cooling effects on the environment (Niemeier et al., 2013) and the incidence of solar radiation absorption (Sánchez & McInnes, 2015). The methods are applied because of their cooling effects on the environment (Niemeier et al., 2013). Thus, SRM options are the only means that can be used to reduce global temperatures at short notice. Both CDR and SRM methods can be applied under different scenarios of climate change, together with other climate change and GHG reduction methods (Lenton & Vaughan, 2009).

Technical Feasibility and Risks of Geoengineering Methods

Geoengineering through the use of CDR methods is, according to the Royal Society (2009), technically feasible, although it could be slow-acting and comparatively expensive. The local risks and direct costs of specific methods would considerably differ but be more effective compared to conventional mitigation (Jones et al., 2013). The technologies for the removal of CO2 are different from the approaches that provide modifications to albedo. The CDR methods usually act slowly in terms of reducing CO2 concentrations compared to SRM, and they deal with the root cause of anthropogenic climate change and the potential consequences.

The Royal Society (2009) noted that “the most desirable CDR techniques are those that remove carbon from the atmosphere without perturbing other Earth system processes and without deleterious land-use change requirements” (p. 149). Thus, the CDR options have the capacity to reduce CO2 emissions. For example, enhanced weathering and engineered air capture techniques are desirable tools, although the possible costs of reducing them are not yet established. Goes et al. (2011) noted that they do not require large-scale land use and huge budgets for changes to be noticed. However, the approaches could take a long period of time. In terms of financial feasibility, the implementation of SRM methods compared to CDR could be technically feasible. This is because the costs of implementation are small when compared to the costs of the effects of foreseeable climate change (Royal Society, 2009). In addition, emissions reduction costs compared to those of implementation are lower, which makes it feasible.

CDR techniques used to sequester carbon from the atmosphere have land-use implications, but research is required to ensure that they are economically viable and socially and ecologically sustainable. On the other hand, CDR methods that are used to intervene directly in Earth systems also require more research to establish if they can sequester CO2 in an affordable and reliable way without experiencing unacceptable side effects (Royal Society, 2009). Nonetheless, indirect costs linked to the impacts of SRM cannot consistently be estimated currently but would require deliberate consideration.

SRM options, if extensively implemented, could realize rapid reductions in global temperatures at a level and rate that could not be realized via normal mitigation measures such as the use of renewable energy resources. Nevertheless, all SRM options, to some extent, are faced with the termination problem, and economic modeling studies have indicated that the resulting climate cannot be the same if CO2 concentrations are minimized (Zhang et al., 2014). For instance, the use of a uniform reduction of solar radiation would result in a reduction in tropical precipitation. Goes et al. (2011) pointed out that there are serious deficiencies in terms of the ability of current models to appraise features such as storms and precipitation with the matching uncertainties in the impacts of SRM. However, there is a likelihood that a high CO2 concentration can be achieved through the use of SRM options in the short term. Therefore, SRM approaches could be useful in the future, provided that the associated risks can be proven to be manageable and acceptable.

Economic Costs and Any Risks of Unintended Consequences

CDR methods are used to remove CO2 and have limited risks because they do not perturb natural systems and do not require the use of large-scale land-use change requirements (Goes, Keller, & Tuana, 2011). For example, the use of CO2 capture has fewer side effects, making it feasible. Techniques used to sequester carbon are useful, economically viable, and socially and ecologically sustainable (refer to Table 2). The reduction of fossil fuel burning through the use of energy-saving and emission-reduction technologies is a direct strategy that can be used in industrial areas to combat the ongoing change in global climate (Cheah et al., 2013). SRM geoengineering, once implemented, has to be maintained because, when it is terminated, there is a possibility to reverse climate change without any significant effects (Zhang et al., 2014).

In comparison to CDR methods, SRM techniques are cheap and, once implemented, are supposed to be effective within a few years (Zhang et al., 2014). Nonetheless, there are considerable uncertainties related to their consequences and extra risks. For example, aerosol geoengineering could potentially violate the requirements of environmental conservation as it may pollute the environment (refer to Table 3). For instance, it may alter regional precipitation patterns and, in the process, threaten people's access to clean and adequate drinking water resources and food. Additionally, the implementation of any SRM on a large scale has the potential to introduce additional risks compared to CDR. Thus, SRM must be used to support CDR methods, which have limited risks and uncertainties. The effects of CDR methods and SRM techniques are presented in tables 2 and 3, respectively.

Table 2: Cost and Environmental Impact of CDR methods. Source: Royal Society. (2009).

From table 2 above, CDR options are associated with low, medium, and high costs, with chemical air capture and carbon sequestration having the highest costs. The risks of unanticipated environmental effects are high in ocean fertilisation and Ocean N and P fertilisation. Harvey (2008) noted that the use of CDR to mitigate atmospheric CO2 has the capacity to increase ocean acidification through the addition of limestone powder to the oceans.

Table 3: Cost And Environmental Impact of SRM methods. Source: Royal Society. (2009).

Most of the SRM options (space-based reflectors, stratospheric aerosols, cloud albedo, and desert surface albedo) have high risks. The possible side effects are the termination effect, reduction in crop yields, ecosystem impacts, regional climate change, and changes in stratosphere chemistry. The Royal Society (2009) noted that there are risks linked with the modification of the oceanic carbon cycle, and it may have effects on food levels, thus affecting the whole ecology of the ocean. SRM techniques are not ideal in terms of dealing with reductions in climate change because they do not address the potential risks

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