Solar Radiation Management
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                                                                 January 25, 2016 jt

 

There are no natural clouds in the pictures above. The white-wisps [thin lines] are produced by chemtrails

1. Introduction
Solar geoengineering is commonly seen to be subject to what some call its ‘incredible economics’ (Barrett
2008) and, more specifically, its ‘free driver’ effect: its direct costs are so cheap compared to its potential
climate impacts so as to reverse many of the properties of the so-called ‘free rider’ problem governing carbon
mitigation decisions and climate policy more broadly (Wagner and Weitzman 2012, 2015, Weitzman 2015).

The governance problem becomes one of cooperation to restrain rather than increase action. Here we probe these economic assertions and review the capabilities and costs of various lofting methods intended to deploy sulfates into the lower stratosphere, the leading proposed method of solar geoengineering (Keith 2000, Crutzen 2006, National Research Council 2015).

Stratospheric Aerosol Injection (SAI) would require lofting hundreds of thousands to millions of tons of material each year to altitudes up to ∼20 km. Here we seek answers to three questions: if SAI deployment were to commence within the foreseeable future with the tools and technologies at our disposal, how would such deployment be physically achieved, how much would it cost, and could it be done in secret?

National Academies of Sciences (NAS), Engineering and Medicine (1992) provides an early review of SAI deployment options, deriving detailed pricing for naval rifles and two different balloon systems (appendix Q.11). McClellan et al (2012) attempt to provide the first comprehensive answer to this question, publishing results from an earlier Aurora Flight
Science Corporation analysis (McClellan et al 2010).

Like McClellan et al (2010, 2012), and later reviewed by Moriyama et al (2017), we explore an array of different SAI lofting technologies and given our more specific mission criteria, we conclude that aircraft are the only reasonable option. Unlike them, we conclude that modified existing business jets are incapable of flying above ∼16 km, a conclusion confirmed directly by the manufacturers of the jets in question.

This directly contradicts both McClellan et al (2010, 2012)and IPCC (2018). The latter demonstrates the large influence McClellan et al’s analysis has had on the broader conversation. IPCC (2018) states that ‘there is high agreement that aircrafts after some modifications could inject millions of tons of SO2 in the lower stratosphere (∼20 km)’ (chapter 4).

IPCC cites three studies in support of that statement, including McClellan et al (2012). However, both of the other two studies, in turn, base their conclusions, in large part, on McClellan et al’s earlier analysis. Irvine et al (2016)
also cites the other (Davidson et al 2012), which, in turn, cites McClellan et al (2010). Robock et al (2009) provides one further independent analysis, reviewing capabilities of military fighters and tankers.

We agree with Robock et al (2009) that military fighters are capable of reaching ∼20 km, but they are incapable of
sustained flight at that altitude (see table 2 below).

We further conclude that no other existing aircraft have the combination of altitude and payload capabilities required for the mission, leading us instead to the design of a new plane.

We propose such a plane and call it SAI Lofter (SAIL), describing its basic specifications and providing detailed cost estimates for its design, manufacture, and operation under a hypothesized solar geoengineering scenario of halving the increase in radiative forcing from a date 15 years hence. We do not seek to foretell future technological breakthroughs, nor do we guess at costs in 50 or 100 years when next-generation deployment technologies would likely become available.

Further, we do not consider solar geoengineering methodologies other than SAI or materials other than sulfate aerosols (Keith 2000, Keith et al 2016). We instead hope to illuminate discussions of direct SAI deployment costs based on existing technologies, thereby facilitating further benefit-cost comparisons and grounding ‘free driver’ discussions in concrete
numbers supported by science-based SAI deployment scenarios and sound aerospace engineering.

2. Stratospheric aerosol deployment scenario

Following a research hypothesis proposed by Keith and Irvine (2016), we consider a limited SAI deployment scenario (Sugiyama et al 2018) intended to cut in half the rate of temperature change from the first year of the program onward.

While such a scenario is less ambitious (and less environmentally risky) than those aimed at keeping temperatures constant from a certain date forward, it is more ambitious than SAI merely holding the rate of temperature change constant (MacMartin et al 2014).

We further assume anthropogenically driven radiative forcing of ∼2.70 W m−2 by 2030, with an assumed decadal increase of ∼0.5 W m−2 that is roughly consistent with the Representative Concentration Pathway (RCP) 6.0 scenario (Moss et al
2010, IPCC 2013). Assuming the desire to cut this rate of increase in half implies the need for SAI to reduce
radiative forcing by ∼0.25 W m−2 by the end of the first decade of deployment. The implied change in global average surface temperatures from SAI deployment is −0.2 K per decade, with an assumed global average temperature sensitivity of 0.8 K per W m−2

We focus on SAI using sulfates, not because they are optimal—they may not be (Keith et al 2016)—but because the long record of prior analyses on both efficacy and risks of sulfate deployment (National Research Council 2015) renders them the best understood and therefore least uncertain material with which to commence in this hypothetical scenario of partial deployment.

In the base case, we assume a topof-atmosphere (TOA) sulfate forcing sensitivity of −0.25 W m−2 per Tg S yr−1 , a value toward the lower end of recent estimates. Pierce et al (2010) estimates −0.34 W m−2 and Dai et al (2018) derives a range from below −0.50 to over −2Wm−2 for injections between 30 °N and 30 °S. Other estimates for different injection scenarios, roughly converted to TOA values, range from −0.15 W m−2 (Kuebbeler et al 2012) to −0.33 W m−2 (Niemeier and Timmreck 2015), while Pitariet al (2014) shows results from the Geoengineering Model Intercomparison Project (GeoMIP), here roughly converted to TOA, for one point of injection at the equator ranging from −0.47 to −0.98 W m−2.

Table 1 summarizes the base-case SAI deployment scenario for the first 15 years of a program commencing in 15 years. The year 2033 is entirely hypothetical.

It is not the most likely start date, nor are we suggesting it is an optimal one, but any deployment much sooner seems highly unlikely based on scientific and political
Table 1.

Hypothesized base-case SAI scenario in the first 15 years of deployment commencing in 15 years. Tons of S carried are half of tons SO2 dispersed.
Year
Unabated
forcing
(W m−2)
Target
forcing
(W m−2)
SO2 dispersed
(Mt)
a Temperature
reduced (K)
b 2033 2.850 2.825 0.2 −0.02
2034 2.900 2.850 0.4 −0.04
2035 2.950 2.875 0.6 −0.06
2036 3.000 2.900 0.8 −0.08
2037 3.050 2.925 1.0 −0.10
2038 3.100 2.950 1.2 −0.12
2039 3.150 2.975 1.4 −0.14
2040 3.200 3.000 1.6 −0.16
2041 3.250 3.025 1.8 −0.18
2042 3.300 3.050 2.0 −0.20
2043 3.350 3.075 2.2 −0.22
2044 3.400 3.100 2.4 −0.24
2045 3.450 3.125 2.6 −0.26
2046 3.500 3.150 2.8 −0.28
2047 3.550 3.175 3.0 −0.30
a Assumes −0.25 W m−2 per Tg S.
b Assumes 0.8 K per W m−2 average temperature sensitivity (see
text).
2

https://iopscience.iop.org/article/10.1088/1748-9326/aae98d/pdf

The Dept. of Solar Radiation Management
Is attempting to block the sun’s heat a good idea—or a reflection on our pathetic efforts to cut carbon emissions?

January 25, 2015 Brian Palmer

Solar Radiation Management (n.): a set of geo-engineering strategies intended to minimize global warming by reflecting the sun’s energy away from the earth.
Solar radiation management sounds like corporate-speak. (VP for Solar Radiation Management, anyone?) In fact, it’s one of the most controversial concepts in climate change mitigation.

The idea is fairly straightforward. First, some Climate Change 101: About 30 percent of the energy arriving from the sun is reflected back out into space, mostly by clouds and ice. The planet—its seas, lands, creatures, buildings, etc.—absorbs the remaining 70 percent, and gases such as carbon dioxide and methane trap some of that heat within the atmosphere. So here’s the pitch for SRM: What if we could bounce more of the sun’s energy back into space in the first place, preventing it from ever getting trapped by the greenhouse effect?

How might we make that happen? One wildly impractical proposal is a network of space mirrors. The problem with this idea isn’t just that it sounds like something a fourth-grader would dream up—it would take a tremendous amount of energy to launch those mirrors into space. (Wasting energy by burning more fossil fuels is precisely what we’re trying to avoid.) Another option is to mist seawater into the air. Those white clouds would reflect solar energy before it reaches the darker, energy-absorbing ocean. This strategy has moderate support among SRM advocates.

To understand the most popular approach, though, think back to the 1991 eruption of Mount Pinatubo in the Philippines, if you can remember it. (I envy your youth if you can’t.) The volcano spewed a huge amount of sulfur dioxide, a precursor of sulfuric acid. Within a year, the sulfuric acid layer stretched around the entire planet. Tiny droplets of sulfuric acid reflected sunlight back into space before it reached earth, and the planet’s temperature dropped by approximately 1 degree Fahrenheit for more than two years.

SRM advocates say we could do something similar—and without killing hundreds of people and displacing thousands more, as Pinatubo’s eruption did. We could fly high-altitude planes or float balloons capable of spraying sulfur dioxide into the atmosphere. (Other chemicals, such as titanium dioxide, are also under consideration.) To offset a doubling of atmospheric CO2, which represents a global temperature increase of between 1.5 and 4.5 degrees Celsius, researchers think we would have to inject around five megatons of sulfur dioxide annually into the atmosphere.

Five megatons sounds like a lot—and it is—but SRM enthusiasts point out that coal-fired power plants already emit nearly 55 megatons of sulfur. This is just a 10 percent increase on that number, and for a good cause.

Are you sold? Not so fast. There are many, many complications, and even the most open-minded conservationists are skeptical of SRM. For one thing, it’s largely unproven. Just because a volcano can do something doesn’t mean we can do it—especially in a controlled fashion. In addition, the effects of SRM are likely to vary by region. The process could make some areas colder than they currently are, depressing agricultural production. Russian farmers, for example, might have something to say about this. SRM might also diminish our motivation to reduce carbon emissions. That’s
an issue because excess carbon causes many problems beyond higher temperatures. The oceans would continue to acidify, for example, killing off species like clams, oysters, and corals, and disrupting marine ecosystems.

For now, think of solar radiation management as the panic room of climate change mitigation. Few people really want to go there, but it’s still tempting to some, especially since our current rate of progress on carbon reduction suggests things could get pretty bad. Let's hope we can turn things around before it comes to that.

onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter. https://www.nrdc.org/onearth/dept-solar-radiation-management