Advancing the Science of Climate Change (2010) / Chapter Skim
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15 Solar Radiation Management
15 Solar Radiation Management
Pages 377-388
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From page 377... ...
For example, whitening clouds, injecting particles into the stratosphere, or putting sunshades in space could increase Earth's reflectivity, thereby reducing incoming solar radiation and offsetting some of the warming associated with increasing GHG concentrations. Although few if any voices are promoting geoengineering as a near-term option to limit the magnitude of climate change, the concept has recently been gaining more serious attention as a possible backstop measure to be used if traditional strategies to limit emissions fail to yield significant emissions reductions or if climate trends become disruptive enough to warrant extreme and risky measures.
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From page 378... ...
HISTORY OF SOLAR RADIATION MANAGEMENT PROPOSALS In November of 1965, the Environmental Pollution Panel of the President's Science Advisory Council (PSAC) for the first time informed a president of the United States about the threats posed by increasing atmospheric CO2 concentrations.
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From page 379... ...
; black arrowheads represent shortwave radiation and are associated with solar radiation management; white and gray arrowheads pointing down correspond to a variety of natural and engineered processes, respectively, for removing CO2 from the atmosphere; the thicker, gray arrowhead pointing up represents enhanced ocean upwelling, which could conceivably help to remove CO2 from the atmosphere by enhancing biological activity at the ocean's surface; and the thinner gray arrowheads correspond to increased cloud conden sation nuclei sources. SOURCE: Lenton and Vaughn (2009)
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From page 380... ...
, as long as such research does not undermine other critical climate research efforts (see the discussion of ethical issues below) , including research on adapting to the impacts of climate change and on conventional strategies for limiting the magnitude of future climate change (i.e., reducing fossil fuel consumption, deforestation, and other activities that contribute to climate forcing)
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From page 381... ...
Stratosphere-Based Options One of the most widely discussed options for SRM involves the injection of sulfate aerosols into the stratosphere, although other types of particles could potentially serve the same function. As discussed in Chapter 6, particles can reflect solar radiation back to space, offsetting some of the warming associated with GHGs.
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From page 382... ...
. Both approaches, if applied on a global scale, could potentially yield a modest cooling effect (The Royal Society, 2009)
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From page 383... ...
For the injection of sulfate aerosols, an additional concern exists: the potential for increased concentrations of stratospheric aerosols to enhance the ability of residual chlorine, left from the legacy of chlorofluorocarbon use, to damage the ozone layer, especially in the early spring months at high latitudes. A sudden increase in stratospheric sulfate aerosol could strongly enhance chemical loss of stratospheric polar ozone for several decades, especially in the Arctic (Tilmes et al., 2008)
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From page 384... ...
, and another recent conference recommended voluntary governance mechanisms and basic principles to guide future geoengineering research (Asilomar Scientific Organizing Committee, 2010) , but international endorsement and formal adoption by relevant research institutions and governments have not been undertaken.
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From page 385... ...
For example, in the case of stratospheric sulfur aerosol injection options, modeling and experiments to improve understanding of how particles aggregate in the stratosphere are needed. Because this and similar basic research questions relevant to climate engineering would also improve fundamental knowledge about the atmosphere, they could contribute more broadly to understanding the physical climate system.
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From page 386... ...
Nevertheless, it is possible to predict and anticipate some of these consequences through a combination of analysis; small-scale de minimis experiments; and climate, Earth system, and integrated assessment modeling. Again, in the case of stratospheric sulfur aerosol injection options, experiments that evaluate how increases in diffuse solar radiation would affect ecosystem productivity or how stratospheric particles might affect the ozone layer could be carried out.
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From page 387... ...
Just as it is a nontrivial exercise to quantitatively attribute observed climate change among different climate forcing agents, distinguishing the effects of intentional climate intervention from other causes of climate change to ascertain the effectiveness of SRM approaches is a nontrivial task. Detection and attribution of climate change, and evaluation of all actions taken to respond, including initial testing, will require enhanced observing systems and analyses covering a wide array of climate and other environmental variables, especially more complete observations of energy flows in Earth's climate system.
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From page 388... ...
. Such an effort would no doubt draw on many of the experts already engaged in climate change research, but would also need to engage new disciplines and expertise to aid in issues related to governance, public acceptance, and ethics.
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