Geoengineering
Geoengineering refers to large-scale interventions aimed at modifying the Earth's climate as a response to global warming. The urgency surrounding climate change has led to discussions about various geoengineering methods, although many of these proposals are considered expensive and impractical. One notable concept is the injection of sulfur dioxide into the stratosphere to mimic volcanic eruptions, which could potentially cool the planet but also raise concerns about acid rain and ozone depletion. Other proposed methods include deploying reflective materials in space, using dust to alter sunlight absorption, and even modifying aircraft engines to intentionally pollute the atmosphere for cooling effects.
Despite the potential benefits, critics warn that geoengineering could divert attention from necessary emissions reductions, potentially leading to increased greenhouse gas output if reliance on these technologies were to diminish. Additionally, research into geoengineering continues amid concerns over its ecological impacts and effectiveness, with initiatives in the United States exploring light-reflection technologies. As the climate crisis intensifies, the debate around the ethical and practical dimensions of geoengineering remains poignant and complex, reflecting diverse perspectives on how best to tackle global warming.
Geoengineering
DEFINITION: Large-scale efforts to modify the earth’s climate as a way of mitigating global warming
The prospect of geoengineering is remote because of the great expense and impracticality of implementing many of the projects that have been proposed, but the fact that these ideas are being discussed is an indication of the urgency of the problem of global warming.
Several ideas involving geoengineering on a grand scale have been proposed as ways to ameliorate anthropogenic (human-caused) global warming. In 2006, Paul Crutzen of the Max Planck Institute for Chemistry in Germany, who won a Nobel Prize in 1995 for showing how industrial gases damage the earth’s ozone shield, gave a fresh airing to ideas described during the 1980s by Wallace S. Broecker, a geoengineering pioneer at Columbia University. Broecker theorized that humans could cool the earth by spreading tons of sulfur dioxide into the stratosphere, as erupting volcanoes occasionally do. The injections, he calculated during the 1980s, would require a fleet of hundreds of jumbo jets and, as a by-product, could increase acid rain. Other scientists argued that sulfur conveyed to the stratosphere, which is dry, would not return to the earth’s surface as acid rain. Crutzen estimated that the annual cost of spreading the sulfur could be as high as fifty billion dollars, or about 5 percent of the world’s annual military spending. The sulfur dioxide would have to be refreshed at least twice per month, as the previous load dispersed.
Proposed Methods of Atmospheric Modification
The so-called sulfur solution had also been raised in a 1991 National Academy of Sciences report on climate change strategies that concluded with consideration of atmospheric modification. Other proposed strategies included the placing of mirrored platforms in orbit to reflect sunlight, the use of guns or balloons to add dust to the to reflect sunlight, and the placing of billions of aluminized, hydrogen-filled balloons in the stratosphere, also to reflect incoming solar radiation.
Additional strategies that have been proposed include the use of aircraft with engines modified to be less efficient (making them intentionally polluting) to maintain a dust cloud between the earth and the sun. In 2006, Roger P. Angel, an astronomer at the University of Arizona, suggested a plan that would involve putting into orbit trillions of small, very thin lenses that would bend sunlight away from the earth.
Such ideas for modifying the earth’s atmosphere probably will remain limited to an intellectual parlor game, because the costs of carrying any of them out would be prohibitively high. In addition to monetary costs, the environmental costs of filling the stratosphere with sulfur dioxide or other pollutants would far outweigh the benefits, even in an increasingly warm and humid world. In the case of the use of sulfur dioxide, scientists have observed that sulfuric acid also tends to attract chlorine atoms, creating a chemical combination that could assist chlorofluorocarbons (CFCs) in devouring stratospheric ozone.
Another proposed solution to global warming that would use sulfur involves the burning of sulfur in ships and power plants to form sulfate aerosols. Mikhail Budyko, a Russian climatologist, proposed a massive atmospheric infusion of sulfur that would form enough sulfur dioxide to wrap the earth in radiation-deflecting thin white clouds within a few months. Budyko posited that the net effect would be to cool the earth in a fashion similar to the massive eruption of the volcano Mount Tambora in 1815, which ejected enough sulfur into the air to produce, in 1816, “the year without a summer.” Crops across New England and upstate New York were devastated by frosts that continued into the summer months, and in the far northern part of New York State frosts were reported into June.
The Atmospheric Chemistry of Sulfur
Suspended particulates caused by emissions of sulfur dioxide and some other urban air pollutants (aerosols) increase the reflectivity of the earth, and thus usually exert a cooling influence on planetary temperatures. When Mount Pinatubo erupted in 1991, about 20 million tons of sulfur were injected into the atmosphere, enough to cool the earth’s near-surface atmosphere about 0.5 degree Celsius (0.9 degree Fahrenheit) for a year or two, or roughly the increase attributable to global warming during the previous century. The physical challenge of lifting that much sulfur into the atmosphere year after year would be very great, especially as increases in the levels of greenhouse gases over time would require more of it.
Further, an increase in atmospheric does not always exert a cooling influence. Researchers working with the National Oceanic and Atmospheric Administration (NOAA) have assembled data indicating that periodic increases in atmospheric dust concentrations during the glacial periods of the past 100,000 years may have resulted in significant regional warming, and that this warming may have triggered some of the abrupt climatic changes observed in paleoclimate records.
Criticisms of Geoengineering Proposals
Aside from causing atmospheric conditions that might contribute to the creation of acid rain, filling the upper atmosphere with sulfur could also deplete stratospheric ozone and reduce overall precipitation, most notably during the African and Indian monsoons, which are crucial for hundreds of millions of subsistence farmers. Implementation of the “sulfur solution” also would reduce pressure on human populations to reduce their greenhouse emissions, making it likely that such emissions would increase. As a result, if the process of injecting sulfur into the atmosphere ever stopped, global warming would accelerate rapidly.
Some scientists object to geoengineering on the grounds that it would remove the pressure on the world’s governments to deal with the problem of global warming at its source—that is, to use energy sources other than fossil fuels. Biochemist Meinrat Andreae of the Max Planck Institute for Chemistry has compared putting sulfur into the stratosphere as a solution to global warming to giving a junkie a fix. Kenneth Caldeira of the Carnegie Institution Department of Global Ecology at Stanford University has stated that the biggest risk of geoengineering is that it eliminates the pressure to decrease greenhouse gases. Others argue that geoengineering could make the earth dependent on a continuing human-provided sulfur “fix,” and if the supply of sulfur should falter, the earth could heat up quickly within a few years.
Scientists have also noted that intentionally polluting the atmosphere to counter surface warming quickly gives rise to other problems. As T. M. L. Wigley of the National Center for Atmospheric Research has observed, global warming and increases in carbon dioxide concentration pose two threats: one from climate change directly and another from increasing acidity of the oceans. While geoengineering might provide a temporary fix for temperature change, it would do nothing about ocean acidity.
Despite these concerns, President Biden’s White House Office of Science and Technology Policy initiated a five year plan in 2022 to further study and develop light-reflection technology to slow global warming, even if only temporarily. Because of the time-sensitive nature of the climate crisis, efforts to stifle these research efforts based on moral grounds were predicted to be less effective in the late 2020s. Methods researched under this effort include stratospheric aerosol injection, marine cloud brightening, and cirrus cloud thinning. In 2024, the nation’s first instance of cloud brightening was performed by University of Washington researchers in San Francisco, California. However, the topic remained controversial among those concerned with the long-term effects of such methods.
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