Wednesday, April 16, 2014

Chapter 3.3.7 - Ethics, and justice - and Chapter 6.9 - CCS, SRM and other geoengineering options including environmental risks (Excerpted from IPCC AR5 WGIII)


Intergovernmental Panel on Climate Change
 Working Group III – Mitigation of Climate Change 

Chapter 3

Social, Economic and Ethical
Concepts and Methods 
3.3.7    Geoengineering, ethics, and justice

Geoengineering (also known as climate engineering [CE]), is largescale technical intervention in the climate system that aims to cancel some of the effects of GHG emissions (for more details see WGI 6.5 and WGIII 6.9). Geoengineering represents a third kind of response to climate change, besides mitigation and adaptation. Various options for geoengineering have been proposed, including different types of solar radiation management (SRM) and carbon dioxide removal (CDR). This section reviews the major moral arguments for and against geoengineering technologies (for surveys see Robock, 2008; Corner and Pidgeon, 2010; Gardiner, 2010; Ott, 2010; Betz and Cacean, 2012; Preston, 2013). These moral arguments do not apply equally to all proposed geoengineering methods and have to be assessed on a casespecific basis.7

Three lines of argument support the view that geoengineering technologies might be desirable to deploy at some point in the future. First, that humanity could end up in a situation where deploying geoengineering, particularly SRM, appears as a lesser evil than unmitigated climate change (Crutzen, 2006; Gardiner, 2010; Keith et al., 2010; Svoboda, 2012a; Betz, 2012). Second, that geoengineering could be a more costeffective response to climate change than mitigation or adaptation (Barrett, 2008). Such efficiency arguments have been criticized in the ethical literature for neglecting issues such as sideeffects, uncertainties, or fairness (Gardiner, 2010, 2011; Buck, 2012). Third, that some aggressive climate stabilization targets cannot be achieved through mitigation measures alone and thus must be complemented by either CDR or SRM (Greene et al., 2010; Sandler, 2012).

Geoengineering technologies face several distinct sets of objections. Some authors have stressed the substantial uncertainties of largescale deployment (for overviews of geoengineering risks see also Schneider (2008) and Sardemann and Grunwald (2010)), while others have argued that some intended and unintended effects of both CDR and SRM could be irreversible (Jamieson, 1996) and that some current uncertainties are unresolvable (Bunzl, 2009). Furthermore, it has been pointed out that geoengineering could make the situation worse rather than better (Hegerl and Solomon, 2009; Fleming, 2010; Hamilton, 2013) and that several technologies lack a viable exit option: SRM in particular would have to be maintained as long as GHG concentrations remain elevated (The Royal Society, 2009). 

Arguments against geoengineering on the basis of fairness and justice deal with the intragenerational and intergenerational distributional effects. SRM schemes could aggravate some inequalities if, as expected, they modify regional precipitation and temperature patterns with unequal social impacts (Bunzl, 2008; The Royal Society, 2009; Svoboda et al., 2011; Preston, 2012). Furthermore, some CDR methods would require largescale land transformations, potentially

7 While the literature typically associates some arguments with particular types of methods (e.g., the termination problem with SRM), it is not clear that there are two groups of moral arguments: those applicable to all SRM methods on the one side and those applicable to all CDR methods on the other side. In other words, the moral assessment hinges on aspects of geoengineering that are not connected to the distinction between SRM and CDR.

competing with agricultural landuse, with uncertain distributive consequences. Other arguments against geoengineering deal with issues including the geopolitics of SRM, such as international conflicts that may arise from the ability to control the global thermostat” (e.g., Schelling, 1996; Hulme, 2009), ethics (Hale and Grundy, 2009; Preston, 2011; Hale and Dilling, 2011; Svoboda, 2012b; Hale, 2012b), and a critical assessment of technology and modern ivilization in general (Fleming, 2010; Scott, 2012).

One of the most prominent arguments against geoengineering suggests that geoengineering research activities might hamper mitigation efforts (e.g., Jamieson, 1996; Keith, 2000; Gardiner,2010), which presumes that geoengineering should not be considered an acceptable substitute for mitigation. The central idea in that research increases the prospect of geoengineering being regarded as a serious alternative to emission reduction (for a discussion of different versions of this argument see Hale, 2012a; Hourdequin, 2012). Other authors have argued, based on historical evidence and analogies to other technologies, that geoengineering research might make deployment inevitable (Jamieson, 1996; Bunzl, 2009), or that largescale field tests could amount to fullfledged deployment (Robock et al., 2010). It has also been argued that geoengineering would constitute an unjust imposition of risks on future generations, because the underlying problem would not be solved but only counteracted with risky technologies (Gardiner, 2010; Ott, 2012; Smith, 2012). The latter argument is particularly relevant to SRM technologies that would not affect greenhouse gas concentrations, but it would also apply to some CDR methods, as there may be issues of longterm safety and capacity of storage.

Arguments in favour of research on geoengineering point out that research does not necessarily prepare for future deployment, but can, on the contrary, uncover major flaws in proposed schemes, avoid premature CE deployment, and eventually foster mitigation efforts (e.g., Keith et al., 2010). Another justification for Research and Development (R&D) is that it is required to help decisionmakers take informed decisions (Leisner and MüllerKlieser, 2010).

Chapter 6  
Assessing Transformation Pathways
6.9   Carbon and radiation management and other geo-engineering options including environmental risks

Some scientists have argued that it might be useful to consider, in addition to mitigation and adaptation measures, various intentional interventions into the climate system as part of a broader climate policy strategy (Keith, 2000; Crutzen, 2006). Such technologies have often been grouped under the blanket term ‘geoengineering’ or, alternatively, ‘climate engineering’(Keith, 2000; Vaughan and Lenton, 2011). Calls for research into these technologies have increased in recent years (Caldeira and Keith, 2010; Science and Technology Committee, 2010), and several assessments have been conducted (Royal Society, 2009; Edenhofer et al., 2011; Ginzky et al., 2011; Rickels et al., 2011). Two categories of geoengineering are generally distinguished. Removal of GHGs, in particular carbon dioxide (termed ‘carbon dioxide removal’ or CDR, would reduce atmospheric GHG concentrations. The boundary between some mitigation and some CDR methods is not always clear (Boucher et al., 2011, 2013). ‘Solar radiation management’ or SRM technologies aim to increase the reflection of sunlight to cool the planet and do not fall within the usual definitions of mitigation and adaptation. Within each of these categories, there is a wide range of techniques that are addressed in more detail in Sections 6.5 and 7.7 of the WG I report. 

Many geoengineering technologies are presently only hypothetical. Whether or not they could actually contribute to the avoidance of future climate change impacts is not clear (Blackstock et al., 2009; Royal Society, 2009). Beyond open questions regarding environmental effects and technological feasibility, questions have been raised about the socio-political dimensions of geoengineering and its potential implications for climate politics (Barrett, 2008; Royal Society, 2009; Rickels et al., 2011). In the general discussion, geoengineering has been framed in a number of ways (Nerlich and Jaspal, 2012; Macnaghten and Szerszynski, 2013; Luokkanen et al., 2013; Scholte et al., 2013), for instance, as a last resort in case of a climate emergency (Blackstock et al., 2009; McCusker et al., 2012), or as a way to buy time for implementing conventional mitigation (Wigley, 2006; Institution of Mechanical Engineers, 2009; MacCracken, 2009). Most assessments agree that geoengineering technologies should not be treated as a replacement for conventional mitigation and adaptation due to the high costs involved for some techniques, particularly most CDR methods, and the potential risks, or pervasive uncertainties involved with nearly all techniques (Royal Society, 2009; Rickels et al., 2011). The potential role of geoengineering as a viable component of climate policy is yet to be determined, and it has been argued that geoengineering could become a distraction from urgent mitigation and adaptation measures (Lin; Preston, 2013).

6.9.1    Carbon dioxide removal    Proposed carbon dioxide removal methods and characteristics

Proposed CDR methods involve removing CO2 from the atmosphere and storing the carbon in land, ocean, or geological reservoirs. These methods vary greatly in their estimated costs, risks to humans and the environment, potential scalability, and notably in the depth of research about their potential and risks. Some techniques that fall within the definition of CDR are also regarded as mitigation measures such as afforestation and BECCS (see Glossary). The term ‘negative emissions technologies’ can be used as an alternative to CDR (McGlashan et al., 2012; McLaren, 2012; Tavoni and Socolow, 2013).

The WG I report (Section 6.5.1) provides an extensive but not exhaustive list of CDR techniques (WG I Table 6.14). Here only techniques that feature more prominently in the literature are covered. This includes (1) increased land carbon sequestration by reforestation and afforestation, soil carbon management, or biochar (see WG III Chapter 11); (2) increased ocean carbon sequestration by ocean fertilization; (3) increased weathering through the application of ground silicates to soils or the ocean; and (4) chemical or biological capture with geological storage by BECCS or direct air capture (DAC). CDR techniques can be categorized in alternative ways. For example, they can be categorized (1) as industrial technologies versus ecosystem manipulation; (2) by the pathway for carbon dioxide capture (e.g. McLaren, 2012; Caldeira et al., 2013); (3) by the fate of the stored carbon (Stephens and Keith, 2008); and (4) by the scale of implementation (Boucher et al., 2013). Removal of other GHGs, e.g., CH4 and N2O, have also been proposed (Boucher and Folberth, 2010; de_Richter and Caillol, 2011; Stolaroff et al., 2012). 

All CDR techniques have a similar slow impact on rates of warming as mitigation measures (van Vuuren and Stehfest, 2013) (see WG I Section 6.5.1). An atmospheric ‘rebound effect’ (see WG I Glossary) dictates that CDR requires roughly twice as much CO2 removed from the atmosphere for any desired  net reduction in atmospheric CO2 concentration, as some CO2 will be returned from the natural carbon sinks (Lenton and Vaughan, 2009; Matthews, 2010). Permanence of the storage reservoir is a key consideration for CDR efficacy. Permanent (larger than tens of thousands of years) could be geological reservoirs while nonpermanent reservoirs include oceans and land (the latter could, among others, be affected by the magnitude of future climate change) (see WG I Section 6.5.1). Storage capacity estimates suggest geological reservoirs could store several thousand GtC; the oceans a few thousand GtC in the long term, and the land may have the potential to store the equivalent to historical landuse loss of 180 ± 80 GtC (also see Table 6.15 of WG I)(Metz et al., 2005; House et al., 2006; Orr, 2009; Matthews, 2010). 

Ocean fertilization field experiments show no consensus on the efficacy of iron fertilization (Boyd et al., 2007; Smetacek et al., 2012). Modelling studies estimate between 15 ppm and less than 100 ppm drawdown of CO2 from the atmosphere over 100 years (Zeebe and Archer, 2005; Cao and Caldeira, 2010) while simulations of mechanical upwelling suggest 0.9 Gt/yr (Oschlies et al., 2010). The latter technique has not been field tested. There are a number of possible risks including downstream decrease in productivity, expanded regions of lowoxygen concentration, and increased N2O emissions (See WG I Section (low confidence). Given the uncertainties surrounding effectiveness and impacts, this CDR technique is at a research phase with no active commercial ventures. Furthermore, current international governance states that marine geoengineering including ocean fertilization is to be regulated under amendments to the London Convention/London Protocol on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, only allowing legitimate scientific research (Güssow et al., 2010; International Maritime Organization, 2013).

Enhanced weathering on land using silicate minerals mined, crushed, transported, and spread on soils has been estimated to have a potential capacity, in an idealized study, of 1 GtC/yr (Köhler et al., 2010). Oceanbased weathering CDR methods include use of carbonate or silicate minerals processed or added directly to the ocean (see WG I Section All of these measures involve a notable energy demand through mining, crushing, and transporting bulk materials. Preliminary hypothetical cost estimates are in the order of 23-66 USD/tCO2 (Rau and Caldeira, 1999; Rau et al., 2007) for land and 51-64 USD/tCO2 for ocean methods (McLaren, 2012). The confidence level on the carbon cycle impacts of enhanced weathering is low (WG I Section 

The use of CCS technologies (Metz et al., 2005) with biomass energy also creates a carbon sink (Azar et al., 2006; Gough and Upham, 2011). The BECCS is included in the RCP 2.6 (van Vuuren et al., 2007, 2011b) and a wide range of scenarios reaching similar and higher concentration goals. From a technical perspective, BECCS is very similar to a combination of other techniques that are part of the mitigation portfolio: the production of bioenergy and CCS for fossil fuels. Estimates of the global technical potential for BECCS vary greatly ranging from 3 to more than 10 GtCO2/yr (Koornneef et al., 2012; McLaren, 2012; van Vuuren et al., 2013), while initial cost estimates also vary greatly from around 60 to 250 USD/tCO2 (McGlashan et al., 2012; McLaren, 2012). Important limiting factors for BECCS include land availability, a sustainable supply of biomass and storage capacity (Gough and Upham, 2011; McLaren, 2012). There is also a potential issue of competition for biomass under bioenergydependent mitigation pathways. Direct air capture uses a sorbent to capture CO2 from the atmosphere and the longterm storage of the captured CO2 in geological reservoirs (GAO, 2011; McGlashan et al., 2012; McLaren, 2012). There are a number of proposed capture methods including adsorption of CO2 using amines in a solid form and the use of wet scrubbing systems based on calcium or sodium cycling. Current research efforts focus on capture methodologies (Keith et al., 2006; Baciocchi et al., 2006; Lackner, 2009; Eisenberger et al., 2009; Socolow et al., 2011) with storage technologies assumed to be the same as CCS (Metz et al, 2005). A U.S. Government Accountability Office (GAO) (2011) technology assessment concluded that all DAC methods were currently immature. A review of initial hypothetical cost estimates, summarizes 40-300 USD/tCO2 for supported amines and 165-600 USD/tCO2 for sodium or calcium scrubbers (McLaren, 2012) reflecting an ongoing debate across very limited literature. Carbon dioxide captured through CCS, BECCS, and DAC are all intended to use the same storage reservoirs (in particular deep geologic reservoirs), potentially limiting their combined use under a transition pathway.    Role of carbon dioxide removal in the context of transformation pathways

Two of the CDR techniques listed above, BECCS and afforestation, are already evaluated in the current integrated models. For concentration goals on the order of 430-530 ppm CO2eq by 2100, BECCS forms an essential component of the response strategy for climate change in the majority of scenarios in the literature, particularly in the context of concentration overshoot. As discussed in Section 6.2.2, BECCS offers additional mitigation potential, but also an option to delay some of the drastic mitigation action that would need to happen to reach lower GHGconcentration goals by the second half of the century.

In scenarios aiming at such lowconcentration levels, BECCS is usually competitive with conventional mitigation technologies, but only after these have been deployed at very large scale (see Azar et al., 2010; Tavoni and Socolow, 2013). At same time, BECCS applications do not feature in less ambitious mitigation pathways (van Vuuren et al., 2011a). Key implications of the use of BECCS in transition pathways is that emission reduction decisions are directly related to expected availability and deployment of BECCS in the second half of the century and that scenarios might temporarily overshoot temperature or concentration goals. 

The vast majority of scenarios in the literature show CO2 emissions of LUC become negative in the second half of the century even in the absence of mitigation policy (see Section 6.3.2). This is a consequence of demographic trends and assumptions on landuse policy. Addition afforestation as part of mitigation policy is included in a smaller set of models. In these models, afforestation measures increase for lowerconcentration categories, potentially leading to net uptake of carbon of around 10 GtCO2/yr.

There are broader discussions in the literature regarding the technological challenges and potential risks of largescale BECCS deployment. The potential role of BECCS will be influenced by the sustainable supply of largescale biomass feedstock and feasibility of capture, transport, and longterm underground storage of CO2 as well as the perceptions of these issues. The use of BECCS faces large challenges in financing, and currently no such plants have been built and tested at scale. Integrated modeling studies have therefore explored the sensitivities regarding the availability of BECCS in the technology portfolio by limiting bioenergy supply or CCS storage (Section

Only a few papers have assessed the role of DAC in mitigation scenarios (e.g. Keith et al., 2006; Keller et al., 2008; Pielke Jr, 2009; Nemet and Brandt, 2012; Chen and Tavoni, 2013). These studies generally show that the contribution of DAC hinges critically on the stringency of the concentration goal, the costs relative to other mitigation technologies, time discounting and assumptions about scalability. In these models, the influence of DAC on the mitigation pathways is similar to that of BECCS (assuming similar costs). That is, it leads to a delay in shortterm emission reduction in favour of further reductions in the second half of the century. Other techniques are even less mature and currently not evaluated in integrated models.

There are some constraints to the use of CDR techniques as emphasized in the scenario analysis. First of all, the potential for BECCS, afforestation, and DAC are constrained on the basis of available land and/or safe geologic storage potential for CO2. Both the potential for sustainable bioenergy use (including competition with other demands, e.g., food, fibre, and fuel production) and the potential to store >100 GtC of CO2 per decade for many decades are very uncertain (see previous section) and raise important societal concerns. Finally, the largescale availability of CDR, by shifting the mitigation burden in time, could also exacerbate intergenerational impacts.

6.9.2    Solar radiation management    Proposed solar radiation management methods and characteristics

SRM geoengineering technologies aim to lower the Earth’s temperature by reducing the amount of sunlight that is absorbed by the Earth’s surface, and thus countering some of the GHG induced global warming. Most techniques work by increasing the planetary albedo, thus reflecting a greater fraction of the incoming sunlight back to space. A number of SRM methods have been proposed:

   Mirrors (or sunshades) placed in a stable orbit between the Earth and Sun would directly reduce the insolation the Earth receives (Early, 1989; Angel, 2006). Studies suggest that such a technology is unlikely to be feasible within the next century (Angel, 2006). 

   Stratospheric aerosol injection would attempt to imitate the global cooling that large volcanic eruptions produce (Budyko and Miller, 1974; Crutzen, 2006; Rasch et al., 2008). This might be achieved by lofting sulphate aerosols (or other aerosol species) or their precursors to the stratosphere to create a highaltitude reflective layer that would need to be continually replenished. Section of WG I assessed that there is medium confidence that up to 4 Wm2 of forcing could be achieved with this approach.

   Cloud brightening might be achieved by increasing the albedo of certain marine clouds through the injection of cloud condensation nuclei, most likely sea salt, , producing an effect like that seen when shiptracks of brighter clouds form behind polluting ships (Latham, 1990; Latham et al.,2008, 2012). Section of WG I assessed that too little was known about marine cloud brightening to provide a definitive statement on its potential efficacy, but noted that it might be sufficient to counter the radiative forcing that would result from a doubling of CO2 levels. 
   Various methods have been proposed that could increase the albedo of the planetary surface, for example in urban, crop, and desert regions (Presidents Science Advisory Committee. Environmental Pollution Panel, 1965; Gaskill, 2004; Hamwey, 2007; Ridgwell et al., 2009). These methods would likely only be possible on a much smaller scale than those listed above. Section of WG I discusses these approaches.

This list is nonexhaustive and new proposals for SRM methods may be put forward in the future. Another method that is discussed alongside SRM methods aims to increase outgoing thermal radiation, reducing incoming solar radiation, through the modification of cirrus clouds (Mitchell and Finnegan, 2009) (see WG I Section 

As SRM geoengineering techniques only target the solar radiation budget of the Earth, the effects of CO2 and other GHGs on the Earth System would remain, for example, greater absorption and re-emission of thermal radiation by the atmosphere (WG I Section 7.7), an enhanced CO2 physiological effect on plants (WG I Section 6.5.4), and increased ocean acidification (Matthews et al., 2009). Although SRM geoengineering could potentially reduce the global mean surface air temperature, no SRM technique could fully return the climate to a preindustrial or lowCO2like state. One reason for this is that global mean temperature and global mean hydrological cycle intensity cannot be simultaneously returned to a preindustrial state (Govindasamy and Caldeira, 2000; Robock et al., 2008; Schmidt et al., 2012; Kravitz et al., 2013; MacMartin et al., 2013; Tilmes et al., 2013). Section 7.7.3 of WG I details the current state of knowledge on the potential climate consequences of SRM geoengineering. In brief, simulation studies suggest that some SRM geoengineering techniques applied to a highCO2 climate could create climate conditions more like those of a lowCO2 climate (MorenoCruz et al., 2011; MacMartin et al., 2013), but the annual mean, seasonality, and interannual variability of climate would be modified compared to the preindustrial climate  (Govindasamy and Caldeira, 2000; Lunt et al., 2008; Robock et al., 2008; BanWeiss and Caldeira, 2010; MorenoCruz et al., 2011; Schmidt et al., 2012; Kravitz et al., 2013; MacMartin et al., 2013). SRM geoengineering that could reduce global mean temperatures would reduce thermosteric sealevel rise and would likely also reduce glacier and icesheet contributions to sealevel rise (Irvine et al., 2009, 2012; Moore et al., 2010).

Model simulations suggest that SRM would result in substantially altered global hydrological conditions, with uncertain consequences for specific regional responses such as precipitation and evaporation in monsoon regions (Bala et al., 2008; Schmidt et al., 2012; Kravitz et al., 2013; Tilmes et al., 2013) . In addition to the imperfect cancellation of GHGinduced changes in the climate by SRM, CO2 directly affects the opening of plant stomata, and thus the rate of transpiration of plants and in turn the recycling of water over continents, soil moisture, and surface hydrology (Bala et al., 2007; Betts et al., 2007; Boucher et al., 2009; Spracklen et al., 2012). 
Due to these broadly altered conditions that would result from an implementation of geoengineering, and based on experience from studies of the detection and attribution of climate change, it may take many decades of observations to be certain whether SRM is responsible for a particular regional trend in climate (Stone et al., 2009; MacMynowski et al., 2011). These detection and attribution problems also imply that field testing to identify some of the climate consequences of SRM geoengineering would require deployment at a sizeable fraction of full deployment for a period of many years or even decades (Robock et al., 2010; MacMynowski et al., 2011).

It is important to note that in addition to affecting the planets climate, many SRM methods could have serious nonclimatic sideeffects. Any stratospheric aerosol injection would affect stratospheric chemistry and has the potential to affect stratospheric ozone levels. Tilmes et al. (2009) found that sulphate aerosol geoengineering could delay the recovery of the ozone hole by decades (WG I Section Stratospheric aerosol geoengineering would scatter light, modifying the optical properties of the atmosphere. This would increase the diffusetodirect light ratio, which would make the sky appear hazier (Kravitz et al., 2012), reduce the efficacy of concentrated solar power facilities (Murphy, 2009), and potentially increase the productivity of some plant species, and preferentially those below the canopy layer, with unknown longterm ecosystem consequences (Mercado et al., 2009). The installations and infrastructure of SRM geoengineering techniques may also have some negative effects that may be particularly acute for techniques that are spatially extensive, such as desert albedo geoengineering. SRM would have very little effect on ocean acidification and the other direct effects of elevated CO2 concentrations that are likely to pose significant risks (see WG I Section 6.5.4).    The relation of solar radiation management to climate policy and transformation pathways
A key determinant of the potential role, if any, of SRM in climate policy is that some methods might act relatively quickly. For example, stratospheric aerosol injection could be deployable within months to years, if and when the technology is available, and the climate response to the resulting changes in radiative forcing could occur on a timescale of a decade or less (e.g. Keith, 2000; Matthews and Caldeira, 2007; Royal Society, 2009; Swart and Marinova, 2010; Goes et al., 2011). Mitigating GHG emissions would affect global mean temperatures only on a multidecadal to centennial timescale because of the inertia in the carbon cycle (van Vuuren and Stehfest, 2013). Hence, it has been argued that SRM technologies could potentially complement mitigation activities, for example, by countering global GHG radiative forcing while mitigation activities are being implemented, or by providing a backup strategy for a hypothetical future situation where shortterm reductions in radiative forcing may be desirable (Royal Society, 2009; Rickels et al., 2011). However, the relatively fast and strong climate response expected from some SRM techniques would also impose risks. The termination of SRM geoengineering forcing either by policy choice or through some form of failure would result in a rapid rise of global mean temperature and associated changes in climate, the magnitude of which would depend on the degree of SRM forcing that was being exerted and the rate at which the SRM forcing was withdrawn (Wigley, 2006; Matthews and Caldeira, 2007; Goes et al., 2011; Irvine et al., 2012; Jones et al., 2013). It has been suggested that this risk could be minimized if SRM geoengineering was used moderately and combined with strong CDR geoengineering and mitigation efforts (Ross and Matthews, 2009; Smith and Rasch, 2012). The potential of SRM to significantly impact the climate on short timescales, at potentially low cost, and the uncertainties and risks involved in this raise important sociopolitical questions in addition to natural scientific and technological considerations in the section above.

The economic analysis of the potential role of SRM as a climate change policy is an area of active research and has, thus far, produced mixed and preliminary results (see Klepper and Rickels, 2012). Estimates of the direct costs of deploying various proposed SRM methods differ significantly. A few studies have indicated that direct costs for some SRM methods might be considerably lower than the costs of conventional mitigation, but all estimates are subject to large uncertainties because of questions regarding efficacy and technical feasibility (Coppock, 1992; Barrett, 2008; Blackstock et al., 2009; Robock et al., 2009; Pierce et al., 2010; Klepper and Rickels, 2012; McClellan et al., 2012). 

However, SRM techniques would carry uncertain risks, do not directly address some impacts of anthropogenic GHG emissions, and raise a range of ethical questions (see WG III Section 3.3.8) (Royal Society, 2009; Goes et al., 2011; MorenoCruz and Keith, 2012; Tuana et al., 2012). While costs for the implementation of a particular SRM method might potentially be low, a comprehensive assessment would need to consider all intended and unintended effects on ecosystems and societies and the corresponding uncertainties (Rickels et al., 2011; Goes et al., 2011; Klepper and Rickels, 2012). Because most proposed SRM methods would require constant replenishment and an increase in their implementation intensity if emissions of GHGs continue, the result of any assessment of climate policy costs is strongly dependent on assumptions about the applicable discount rate, the dynamics of deployment, the implementation of mitigation, and the likelihood of risks and sideeffects of SRM (see Bickel and Agrawal, 2011; Goes et al., 2011). While it has been suggested that SRM technologies may buy time for emission reductions (Rickels et al., 2011), they cannot substitute for emission reductions in the long term because they do not address concentrations of GHGs and would only partially and imperfectly compensate for their impacts.

The acceptability of SRM as a climate policy in national and international sociopolitical domains is uncertain. While international commitment is required for effective mitigation, a concern about SRM is that direct costs might be low enough to allow countries to unilaterally alter the global climate (Bodansky, 1996; Schelling, 1996; Barrett, 2008). Barrett (2008) and Urpelainen (2012) therefore argue that SRM technologies introduce structurally obverse problems to the freerider issue in climate change mitigation. Some studies suggest that deployment of SRM hinges on interstate cooperation, due to the complexity of the climate system and the unpredictability of outcomes if states do not coordinate their actions (Horton, 2011). In this case, the political feasibility of an SRM intervention would depend on the ability of statelevel actors to come to some form of agreement. 

The potential for interstate cooperation and conflict will likely depend on the institutional context in which SRM is being discussed, as well as on the relative importance given to climate change issues at the national and international levels. Whether a broad international agreement is possible is a highly contested subject (see Section 13.4.4) (EDF; The Royal Society; TWAS, 2012). Several researchers suggest that a UNbased institutional arrangement for decision making on SRM would be most effective (Barrett, 2008; Virgoe, 2009; Zürn and Schäfer, 2013). So far there are no legally binding international norms that explicitly address SRM, although certain general rules and principles of international law are applicable (see WG II, Chapter 13, p.37). States parties to the UN Convention on Biological Diversity have adopted a nonbinding decision on geoengineering that establishes criteria that could provide guidance for further development of international regulation and governance (CBD Decision IX/16 C (ocean fertilization) and Decision X/33(8)(w); see also LC/LP Resolutions LCLP.1(2008) and LCLP.2(2010), preamble). 

Commentators have identified the governance of SRM technologies as a significant political and ethical challenge, especially in ensuring legitimate decision making, monitoring, and control (Victor,2008; Virgoe, 2009; Bodansky, 2012). Even if SRM would largely reduce the global temperature rise due to anthropogenic climate change, as current modelling studies indicate, it would also imply a spatial and temporal redistribution of risks. SRM thus introduces important questions of intra and intergenerational justice, both distributive and procedural (see Wigley, 2006; Matthews and Caldeira, 2007; Goes et al., 2011; Irvine et al., 2012; Tuana et al., 2012; Bellamy et al., 2012; Preston, 2013).

Furthermore, since the technologies would not remove the need for emission reductions, in order to effectively ameliorate climate change over a longer term SRM regulation would need to be based on a viable relation between mitigation and SRM activities, and consider the respective and combined risks of increased GHG concentrations and SRM interventions. The concern that the prospect of a viable SRM technology may reduce efforts to mitigate and adapt has featured prominently in discussions to date (Royal Society, 2009; Gardiner, 2011; Preston, 2013).
Whether SRM field research or even deployment would be socially and politically acceptable is also dependent on the wider discursive context in which the topic is being discussed. Bellamy et al. (2013) show that the success of mitigation policies is likely to have an influence on stakeholder acceptability of SRM. While current evidence is limited to few studies in a very narrow range of cultural contexts, in a first review of early studies on perceptions of geoengineering, Corner et al. (2012) find that participants of different studies tend to prefer CDR over SRM and mitigation over geoengineering.

Considerations that influence opinions are, amongst others, the perceived ‘naturalness’ of a technology, its reversibility, and the capacity for responsible and transparent governance (Corner et al., 2012). Furthermore, the way that the topic is framed in the media and by experts plays an important role in influencing opinions on SRM research or deployment (Luokkanen et al., 2013; Scholte et al., 2013). The direction that future discussions may take is impossible to predict, since deepened and highly differentiated information is rapidly becoming available (Corner et al., 2012; Macnaghten and Szerszynski, 2013).

6.9.3    Summary

Despite the assumption of some form of negative CO2 emissions in many scenarios, including those leading to 2100 concentrations approaching 450 ppmv CO2eq, whether proposed CDR or SRM geoengineering techniques can actually play a useful role in transformation pathways is uncertain as the efficacy and risks of many techniques are poorly understood at present. CDR techniques aim to reduce CO2 (or potentially other GHG) concentrations. A broad definition of CDR would cover afforestation and BECCS, which are sometimes classified as mitigation techniques, but also proposals that are very distinct in terms of technical maturity, scientific understanding, and risks from mitigation such as ocean iron fertilization. The former are often included in current integrated models and scenarios and are, in terms of their impact on the climate, directly comparable with techniques that are considered to be conventional mitigation, notably fossil CCS and bioenergy use. Both BECCS and afforestation may play a key role in reaching lowGHG concentrations, but at a large scale have substantial landuse demands that may conflict with other mitigation strategies and societal needs such as food production. Whether other CDR techniques would be able to supplement mitigation at any significant scale in the future depends upon efficacy, cost, and risks of these techniques, which at present are highly uncertain. The properties of potential carbon storage reservoirs are also critically important, as limits to reservoir capacity and longevity will constrain the quantity and permanence of CO2 storage. Furthermore, some CDR techniques such as ocean iron fertilization may pose transboundary risks. The impacts of CDR would be relatively slow: climate effects would unfold over the course of decades.

In contrast to CDR, SRM would aim to cool the climate by shielding sunlight. These techniques would not reduce elevated GHG concentrations, and thus not affect other consequences of highGHG concentrations, such as ocean acidification. Some SRM proposals could potentially cause a large cooling within years, much quicker than mitigation or CDR, and a few studies suggest that costs might be considerably lower than CDR for some SRM techniques. It has thus been suggested that SRM could be used to quickly reduce global temperatures or to limit temperature rise while mitigation activities are being implemented. However, to avoid warming, SRM would need to be maintained as long as GHG concentrations remain elevated. Modelling studies show that SRM may be able to reduce global average temperatures but would not perfectly reverse all climatic changes that occur due to elevated GHG concentrations, especially at local to regional scales. For example, SRM is expected to weaken the global hydrological cycle with consequences for regional precipitation patterns and surface hydrology, and is expected to change the seasonality and variability of climate. Because the potential climate impacts of any SRM intervention are uncertain and evidence is very limited, it is too early to conclude how effective SRM would be in reducing climate risks. SRM approaches may also carry significant nonclimatic sideeffects. For example, sulphate aerosol injection would modify stratospheric chemistry, potentially reducing ozone levels, and would change the appearance of the sky. The risks of SRM interventions and largescale experiments, alongside any potential benefits, raise a number of ethical and political questions that would require public engagement and international cooperation to address adequately.  

6.10   Gaps in knowledge and data

The questions that motivate this chapter all address the broad characteristics of possible longterm transformation pathways toward stabilization of GHG concentrations. The discussion has not focused on today’s global or countryspecific technology strategies, policy strategies, or other elements of a nearterm strategy. It is therefore within this longterm strategic context that gaps in knowledge and data should be viewed. Throughout this chapter, a number of areas of further development have been highlighted. Several areas would be most valuable to further the development of information and insights regarding longterm transformation pathways.

These include the following: development of a broader set of socioeconomic and technological storylines to support the development of future scenarios; scenarios pursuing a wider set of climate goals including those related to temperature change; more mitigation scenarios that include impacts from, and adaptations to, a changing climate, including energy and landuse systems critical for mitigation; expanded treatment of the benefits and risks of CDR and SRM options; expanded treatment of cobenefits and risks of mitigation pathways; improvements in the treatment and understanding of mitigation options and responses in enduse sectors in transformation pathways; and more sophisticated treatments of land use and land usebased mitigation options in mitigation scenarios. In addition, a major weakness of the current integrated modelling suite is that regional definitions are often not comparable across models. An important area of advancement would be to develop some clearly defined regional definitions that can be met by most or all models.

6.11   Frequently Asked Questions

FAQ 6.1. Is it possible to bring climate change under control given where we are and what options are available to us? What are the implications of delaying mitigation or limits on technology options? 

Many commonly discussed concentration goals, including the goal of reaching 450 ppm CO2eq by the end of the 21st century, are both physically and technologically possible. However, meeting longterm climate goals will require largescale transformations in human societies, from the way that we produce and consume energy to how we use the land surface, that are inconsistent with both longterm and shortterm trends. For example, to achieve a 450 ppm CO2eq concentration by 2100, supplies of lowcarbon energy energy from nuclear power, solar power, wind power, hydroelectric power, bioenergy, and fossil resources with carbon dioxide capture and storage might need to increase fivefold or more over the next 40 years. The possibility of meeting any concentration goal therefore depends not just on the available technologies and current emissions and concentrations, but also on the capacity of human societies to bear the associated economic implications, accept the associated rapid and largescale deployment of technologies, develop the necessary institutions to manage the transformation, and reconcile the transformation with other policy priorities such as sustainable development. Improvements in the costs and performance of mitigation technologies will ease the burden of this transformation. In contrast, if the world’s countries cannot take on sufficiently ambitious mitigation over the next 20 years, or obstacles impede the deployment of important mitigation technologies at large scale, goals such as 450 ppm CO2eq by 2100 may no longer be possible. 

FAQ 6.2. What are the most important technologies for mitigation? Is there a silver bullet

Limiting CO2eq concentrations will require a portfolio of options, because no single option is sufficient to reduce CO2eq concentrations and eventually eliminate net CO2 emissions. Options include a range of energy supply technologies such as nuclear power, solar energy, wind power, and hydroelectric power, as well as bioenergy and fossil resources with carbon dioxide capture and storage. A range of enduse technologies will be needed to reduce energy consumption, and therefore the need for lowcarbon energy, and to allow the use of lowcarbon fuels in transportation, buildings, and industry. Halting deforestation and encouraging an increase in forested land will help to halt or reverse LUC CO2 emissions. Furthermore, there are opportunities to reduce nonCO2 emissions from land use and industrial sources. Many of these options must be deployed to some degree to stabilize CO2eq concentrations. A portfolio approach can be tailored to local circumstances to take into account other priorities such as those associated with sustainable development. At the same time, if emissions reductions are too modest over the coming two decades, it may no longer be possible to reach a goal of 450 ppm CO2eq by the end of the century without largescale deployment of carbon dioxide removal technologies. Thus, while no individual technology is sufficient, carbon dioxide removal technologies could become necessary in such a scenario.

FAQ 6.3. How much would it cost to bring climate change under control?

Aggregate economic mitigation cost metrics are an important criterion for evaluating transformation pathways and can indicate the level of difficulty associated with particular pathways. However, the broader socioeconomic implications of mitigation go beyond measures of aggregate economic costs, as transformation pathways involve a range of tradeoffs that link to other policy priorities. Global mitigation cost estimates vary widely due to methodological differences along with differences in assumptions about future emissions drivers, technologies, and policy conditions. Most scenario studies collected for this assessment that are based on the idealized assumptions that all countries of the world begin mitigation immediately, there is a single global carbon price applied to wellfunctioning markets, and key technologies are available, find that meeting a 430-480 ppm CO2eq goal by century’s end would entail a reduction in the amount global consumers spend of 1-4% in 2030, 2-6% in 2050, and 3-11% in 2100 relative to what would happen without mitigation. To put these losses in context, studies assume that consumption spending might grow from four to over tenfold over the century without mitigation. Less ambitious goals are associated with lower costs this century. Substantially higher and lower estimates have been obtained by studies that consider interactions with preexisting distortions, nonclimate market failures, and complementary policies. Studies explicitly exploring the implications of lessidealized policy approaches and limited technology performance or availability have consistently produced higher cost estimates. Delaying mitigation would reduce nearterm costs; however studies indicate that subsequent costs will rise much more rapidly to higher levels.

The complete chapters and report here:

Chapter 3 
Social, Economic and Ethical
Concepts and Methods 

Chapter 6  
Assessing Transformation Pathways

Final Draft:
Climate Change 2014: Mitigation of Climate Change
IPCC Working Group III Contribution to AR5

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A #Geoengineering #Climate Issues blog - Geoingeniería by Oscar and Jocelyn Escobar is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.Licencia Creative Commons
A #Geoengineering #Climate Issues blog por Oscar y Jocelyn Escobar se distribuye bajo una Licencia Creative Commons Atribución-NoComercial 4.0 Internacional.