Solar Geoengineering: A Solution Without a Plan Peter Lorenz E-103:The Challenge of Human Induced May 8, 2020

Abstract

Solar Geoengineering refers to a set of technologies that seek to alter Earth's natural reflective balance as a means to mitigate the warming impact of greenhouse gases. Since this novel intervention does not require a dramatic decrease in emissions, Solar radiation management (SRM), will likely become a possible intervention to fight climate change and its effects. Therefore, this paper will outline current research on sulfuric aerosol injections as a specific type of solar geoengineering, discuss externalities and implementation pathways, and outline a plan to promote sound governance with this emerging pathway.

I. Introduction

Climate Change and global warming represent direct threats to human and other life on

Earth (Robock, 2014). A 2015 US National Research Council Report on climate intervention recommended the primary course of action to be mitigation (e.g. ceasing extraction), adaptation and removal. Therefore, current solutions or interventions rely on individuals acting sustainably and reconsidering their environmental priorities, as policy makers and governments attempt to enact subsequent global policy.

However ideal this may be, the current mitigation plans are not anticipated to meet the benchmark of maintaining warming to only two degrees celsius above the pre industrial global average (Aengenheyster, Feng, Ploeg, & Dijkstra, 2018). Alternatively, solar radiation management (SRM), a type of geoengineering, does not rely on reducing emissions to decrease climate change impacts. Instead of addressing the root causes, SRM looks to delay effects of climate change by altering the constraints of the Earth. This may be possible through the introduction of chemicals (e.g sulfur dioxide) into the to mitigate anthropogenic climate change (SRMGI, 2020). Additionally, its effects are thought to be quicker and would not require a change in human behavior in the way other climate change interventions work to promote sustainable societies (Aengenheyster, Feng, Ploeg, & Dijkstra, 2018).

This paper does not purport to encourage a move away from addressing the root causes of climate change and the importance of sustainable living. Instead this author looks into the possibility of SRM as an innovative means of overcoming climate change and its current obstacles including political support and enforcement, fossil fuel industry interests, and individual’s inability to reduce activities of daily living that contribute to greenhouse gas

emission. This approach understands the real possibility that geoengineering interventions are likely to be an increased consideration amongst policy makers in the future (Stephens and

Surprise, 2020).

However, the outcomes of such chemical interventions are still largely unknown (Smith and Wagner, 2018). It is imperative that the enticing potential of solar geoengineering not be explored without understanding its possibilities, limits, and consequences. The current technologies of solar radiation management (SRM) lack a global policy framework and, most importantly, implementation of SRM technologies carries a broad risk to the entire global community. The paper seeks to better understand SRM on both the scientific and policy level. It will discuss the atmospheric understanding by which SRM affects the environment, current research, and future concerns regarding deployment scenarios and global policies governing implementation.

II. Specification of Geoengineering

Geoengineering is a general term that encompasses an assortment of technologies to address climate change through the implementation of technology based solutions. Two main forms of geoengineering are Solar Geoengineering and Greenhouse Gas Removal (SRMGI,

2020). Solar geoengineering or solar radiation management (SRM), looks to reflect a portion of the sun’s energy back into space to counteract the temperature rise associated with increased levels of GHG in the atmosphere (Robock, 2014; Smith and Wagner, 2018; SRMGI, 2020).

GHG absorb energy through solar radiation reflected off the Earth’s surface and trap the excess heat energy, which causes a global rise in temperature (Robock, 2014). Greenhouse Gas

Removal aims to remove carbon dioxide and other GHG from the atmosphere to lessen the

negative impacts (e.g. warming) of the greenhouse effect and (SRMGI,

2020).

Figure 1. Select Types of Geoengineering Interventions (Lorenz, 2020)

One type of SRM technology includes the deployment of sulfur oxide into the stratosphere, known as stratospheric aerosol injections (SAI). These particles circulate the planet via stratospheric winds and reflect portions of the inbound solar radiation as a means to cool the planet (Robock, 2014). Due to the global impact of implementation, feasibility and probability of implementation, this paper will focus on SAI.

III. Stratospheric Sulfur Aerosols

Stratospheric sulfur aerosols are a naturally occurring concentration in the atmosphere that results from the photochemical decomposition of atmospheric gases containing sulfur

(USGS, 2019). Sulfur aerosols are a mixture of sulfuric acid and water that are located in the

“Junge Layer” of the earth’s atmosphere (Junge et al., 1961). The Junge Layer, discovered in

1960, is a layer of microscopic aerosol particles between the tropopause and upper stratosphere

and located at approximately 18 miles (30 km) altitude (Junge et al., 1961). Figure 1 illustrates the layers of the Earth's atmosphere and the approximate altitude of each layer.

(Figure 2: University of Georgia, 2017)

The natural occurrence of sulfur aerosols can be traced back to sulfur dispersions in the stratosphere which occur as a result of the eruptions of volcanoes on Earth’s surface (USGS,

2019). When an eruption of 4 or greater on the Volcanic Explosivity Index occurs, sulfur aerosols form as a result of the eruption force, causing an injection of sulfur dioxide into the stratosphere (USGS, 2019). Figure 2 depicts the eruption of a and the dispersal of erupted materials and gases into the stratosphere (University of Georgia, 2017). The dispersion

of sulfur dioxide (SO2) and subsequent conversion into sulfuric acid (H2SO4) has numerous ​ ​ ​ ​ ​ ​ effects on the climate and the earth's environment (USGS, 2019). Upon the conversion of sulfur

dioxide (SO2 ) into sulfuric acid (H2SO4), the sulfuric acid condenses in the stratosphere and ​ ​ ​ ​ ​ ​ ​ forms sulfate aerosols. While the dispersion of carbon dioxide (CO2), ash, HCl and HF cause a ​ ​

variety of human health and environmental impacts however the purpose of this paper this author elicits to restrict the scope to the sulfur aerosols.

(Figure 3: USGS, 2019)

The key property of sulfur aerosols is its ability to reflect sunlight (Robock, 2014) (SRMGI,

2020). As a result of the reflective properties, there is a reduction in the amount of sunlight reaching the Earth's surface once the aerosols reach a critical mass in the stratosphere. Figure 3 illustrates the observed change in solar radiation transmitted to Mauna Loa Observatory following major volcanic eruptions.

(Figure 4, NOAA 2019)

The presence of aerosols in the stratosphere causes an increase in the amount of solar radiation reflected back into space, which results in a cooling of the Earth's troposphere (Robock,

2014) (SRMGI, 2020). This reduction in the amount of sunlight reaching the Earth’s surface is also known as the cooling effect (National Academy of Sciences,1992). Such a cooling effect ​ ​ can be observed following major volcanic eruptions (Newhall, Hendley, & Stauffer, 1997). For ​ ​ example, the 1991 eruption of Mount Pinatubo in the Philippines caused an estimated 20 million ​ tons of sulfur dioxide (SO2) to be collected in the stratosphere (Newhall, Hendley, & Stauffer, ​ ​ 1997). The Mount Pinatubo eruption was the second-largest terrestrial eruption of the 20th ​ century and led to a 0.5 Celsus decrease in the global temperature between 1991 and 1993 as a ​ result of the material dispersed during the eruption (Newhall, Hendley, & Stauffer, 1997).

IV. Research and Current Experiments

As detailed above, the interaction of sulfuric aerosols and solar radiation has the potential to reduce total solar radiation entering the Earth’s atmosphere and thereby reduce the global temperature. However, currently the technology required to implement a full scale anthropogenic

SRM project does not exist (Smith and Wagner, 2018). These projects aim to replicate the natural occurrence of large volcanic eruptions in a variety of ways, yet/and the foundation for each technology is based on emulating the cooling effect of sulfur aerosols in the stratosphere

(Smith and Wagner, 2018).

The most well researched and most probable implementation for solar radiation management is the injection of sulfur dioxide into the stratosphere via airplane or high altitude balloons. The original idea to inject sulfur in the stratosphere as a means to modify the climate and artificially cool the earth originates from Russian climatologist Mikhail Budyko in 1974

(Robock, 2014). Dr. Budyko estimated that the dispersion of 200,000 tons of sulfur in the stratosphere would offset the warming that occurred between 1920 and 1940 (Robock, 2014) .

By 1992, geoengineering was a focus area for the US National Research Council which produced a comprehensive list of implementation options. These options form the foundation of the research that is being carried out today on the topic (National Academy of Sciences,1992).

In 2014, Dr. in conjunction with the Geoengineering Model

Intercomparison Project, published a paper discussing the current pathways towards implementation. Dr. Robock stated “stratospheric geoengineering considered naval guns, hydrogen and hot air balloons and airplanes for delivery.” Since the publication of Dr. Robock’s paper, the most supported methods of delivery for sulfur dioxide have become military fueling air tankers type aircraft or large format drone aircrafts. Figure 5 is an artistic version of the various SAI implementation techniques considered by Dr. Robock.

Figure 5: (Robock, 2014) However, there is a preference towards aircraft delivery for two reasons. First, by leveraging existing technological and design pathways, the creation of purpose built aircrafts made specifically for high altitude dispersion is more feasible. Secondly, the required injection amounts are in the millions of tons (Mt) and require around the clock trips to deliver the necessary payload (Smith and Wagner, 2018). A study completed by the Pacific Northwest

National Laboratory (PWNL) estimated that the required amount of dispersed SO2 to maintain ​ ​ the current global temperature would need to be increased every year after initial deployment

(Kravitz et al., 2017). The PWNL models indicated that the total global amount required to

maintain 2020 global temperatures would require 51 teragrams (Tg) of SO2 by the year 2099 ​ ​

(Kravitz et al., 2017). Therefore the previous technologies put forth by Dr. Robock are unlikely to be feasible given the constant nature and payloads required for SAI to reduce global average temperatures.

In a study of the SAI implementation costs, Smith and Wagner estimated that it would

-1 cost approximately $2.25 billion USD to fund around 4,000 yr ​ flights for 15 years dispersing 24 ​

Mt of SO2 . While the program cost of around $2.25 billion USD is sizable, it is comparably ​ ​ lower than the cost of climate disasters between 2016 and 2019 ($650 billion USD). Moreover, current calculations indicate that global warming will cause $54 trillion USD in property damage alone by 2040 (DiChristopher, 2019). It is easy to recognize that the monetary cost of a business-as-usual scenario will quickly outpace the financial cost to implement SAI.

A. Funding and Research Centers

Research for solar geoengineering is guided and limited by funding and the interests of funding sources. The current epicenter for SRM research and global policy is the Harvard Solar

Geoengineering Research Program (HSGRP). Dr. , a professor of applied physics at the Harvard School of Engineering and Applied Sciences and professor of public policy at

Harvard Kennedy School, leads a team to “produce research that advances solar geoengineering science and technological frontiers, publish high-impact papers and disseminate ideas that were taken up by other researchers and government research programs” (HSGRP, 2019). Currently, the HSGRP is the world’s highest funded program for solar geoengineering (HSGRP, 2019).

Between 2008 and 2019, HSGRP documented $60 million in global solar geoengineering funding, of which $16,225,000 was granted to start the HSGRP with an additional $7,765,000 allocated to Harvard for the Fund for Innovative Climate Energy Research (HSGRP, 2019).

The concentration of research and global funding for solar geoengineering within the confines of Harvard University are themselves not especially problematic. Dr. Keith has been advancing solar geoengineering research and policy since his publication of “A Serious Look at

Geoengineering” in 1991 and is considered to be one of the leaders in the field of geoengineering

(Keith and Dowlatabadi, 1991). However, the concentration of research and available funding within the Global North, may lead to problems regarding access to information and unequal power dynamics between populations currently experiencing vulnerability to climate change in the Global South (e.g. Bangladesh, Kiribati, Tuvalu) and the countries pursuing research in SRM and geoengineering (Stephens and Surprise, 2020).

V. Concerns and Governance

As stated by the UK Royal Society (2009), “the greatest challenge to successful deployment of geoengineering may be social, ethical, legal and political issues rather than scientific or technical issues.” When considering the global implications of SAI, it is easy to see how a wide range of stakeholder priorities must be considered when researching SAI. Dr.

Robock (2014) raises an important set of questions regarding SAI deployment, “Where to set the global thermostat? Who decides to carry out geoengineering? For whose benefit would the decision be made?”

Unlike research confined to laboratories and classrooms, the decision to further the practical research of SAI falls within the influence of power and politics. Recently, calls to expand research methods to include small batches of SAI have grown to include the UK Royal

Society, American Meteorology Society, American Geophysical Union as well as academic leaders in Germany, Japan and the UK (Robock, 2015). The rise in awareness of the

environmental potential of SAI as a climate change mitigation requires a set of necessary conditions to be applied to SAI research and SRM implementation (Stephens and Surprise,

2020).

The governance structure of geoengineering is difficult for numerous reasons. Primarily, the mechanism by which large scale deployment occurs is transboundary and the subsequent effect is applied to the entire global community (Robock, 2015). At present, each individual nation state maintains their independence and authority regarding achieving their national environmental targets. Signatories of the Paris Climate Agreement and the United Nations

Sustainable Development Goals currently exist as global frameworks and thought models that may allow for a global compact on SRM research and implementation.

These two models are presented as they provide a forum by which stakeholders are able to present their priorities, outline risks and guide policy. Currently, the challenge with SAI governance lies within the inequality of resources between the Global North and Global South

(Stephens and Surprise, 2020). This is problematic as research and funding for SRM is concentrated in the Global North, but, according to the IPCC RCP 8.5, the nations first permanently affected by climate change are located in the Global South. Therefore, a scenario in which a country that is unable to fund research into SRM may likely be among the first nations to push for implementation as a means of survival (Stephens and Surprise, 2020). Thereby, an ethical dilemma exists in which the nations that fund research into SAI are unlikely to enact

SRM before these countries face irreversible impacts of climate change due to their own lower risk of sea level rise, extreme temperature, etc (Stephens and Surprise, 2020).

A secondary concern regarding SAI and other geoengineering technologies is the case of a “” for researchers and policy makers (Robock, 2015). The “moral hazard” is chiefly a response to growing financial support towards the expansion of SRM research, which may detract from other efforts to mitigate climate change and research additional solutions related to human behavioral choices. Areas such as Carbon Capture and Storage or geoengineering provide technological solutions that require no changes in behavior which have caused the current climate crisis. Therefore, the pursuit of technological based solutions, may only serve to further delay the required changes to social and economic systems to preserve the

Earth’s environment (Robock, 2015).

Lastly, the final concern of SAI is related to its uncertain environmental and human health outcomes in the short and long term (Effiong and Neitzel, 2016). Pulmonologists have done extensive work on the human health effects of the chemical that are necessary for SAI

(Effiong and Neitzel, 2016). Sulfur and metallic particles can be deadly in small quantities to humans and when inhaled or ingested cause long term health outcomes such as cancer (Effiong and Neitzel, 2016). Additionally, as we have seen with the current COVID-19 epidemic, certain populations carry an enhanced pulmonary risk due to their location, socio economic standing, access to health facilities and income level. Therefore, if negative externalities occur during the deployment of SAI, it must be heavily considered that the Global South, vulnerable, and marginalized populations will be greatly burdened by these potential health outcomes (Effiong and Neitzel, 2016). The potential risk that air pollution may result from SRM technology must continue to be evaluated and public health planning must occur prior to SAI implementation.

V. Conclusion

Solar Geoengineering, or solar radiation management, has the potential to reduce the global impacts of anthropogenic climate change by reducing the warming effects of greenhouse gases (GHG) (Robock, 2015). Although it is less known to the general population, its scientific possibilities are advancing with a great deal of funding. The promising outcomes paired with its lower overall financial cost, speed of results, and the ability to maintain societies' current lifestyle and demands makes SAI an attractive, innovative idea for mitigation.

However, It is also clear that SAI poses significant risks to vulnerable, marginalised, and less wealthy or powerful communities and nations (Robock, 2015). Therefore, risks must be ethically weighed against the benefits. However, this decision becomes even more problematic since privileged actors in the Global North are largely in charge of research and policy in this area. In many ways, SAI seems like a solution that seemingly provides solutions to our current climate change problems, while creating or reinforcing more already existing social, political, health, and human rights inequalities (Stephens and Surprise, 2020).

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