Climate engineering refers to the deliberate manipulation of the atmosphere to alter the climate in ways that are desirable. A well-known example is cloud seeding, or the addition of particles to the atmosphere in an effort to encourage precipitation. Cloud seeding is climate engineering on a small scale. Other atmospheric alterations are global in scale.
Climate engineering is an attempt to correct things that are going wrong in the atmosphere. If, as many climate scientists accept, the undesirable atmospheric changes have been at least partly the result of human activities that have polluted the atmosphere with compounds that increase the ability of the atmosphere to retain heat, then climate engineering is one attempt to repair the problems that humans have caused.
Engineered change in climate can also involve strategies here on the ground. Examples include diverting the course of rivers, altering wildlife migration patterns, and planting trees to increase the trapping of carbon dioxide (CO2).
Historical Background and Scientific Foundations
In 1945, a gathering of scientists at Princeton University in New Jersey agreed that manipulating climate was possible. Their motivation was a desire to control the weather as a means of decreasing crop production, particularly in the Soviet Union. This was seen as a way of dealing with the perceived military threat posed by the Soviet Union to the United States. Indeed, during the Cold War (1945–1991) that took place between the two nations, the United States conducted research on what was called climatological warfare. This research was actually tested in the field, when cloud seeding was tried unsuccessfully in the early 1970s during the Vietnam war (1954–1975) to bog down Vietcong troop movements.
In cloud seeding, particles of silver iodide (AgI) are scattered into clouds from an airplane. The particles act as surfaces, on which water vapor precipitates to form raindrops. If the drops are heavy enough, they will fall as rain or snow.
Although cloud seeding can sometimes induce rainfall, it is still too unpredictable for routine use. In addition, as argued in court cases, the deliberate production of rainfall in one region robs those downwind of the moisture.
As of 2007, there is concern over the warming of the Arctic and the melting of the polar ice cap. However, in the early 1960s, a few scientists proposed to melt the northern ice cap by spreading dust or soot, the aim being to provide open water for polar navigation (primarily military). However, even then the majority of scientists cautioned against such actions, arguing that so little was known of climatic interactions that an unforeseen and undesirable consequence could occur.
By the 1970s, the warming of the atmosphere had been discovered and the notion that human activities were the cause was gaining some support. Schemes to spread reflective material on the ocean surface or seeding the atmosphere to promote the formation of sunlight-reflecting clouds had been proposed.
Other climate engineering schemes were intended to trap CO2 so that the gas would not accumulate in the atmosphere. The massive planting of trees would produce forests capable of soaking up carbon. Adding nutrients to the ocean could fuel the growth of carbon-absorbing plankton, which would transport the carbon to the ocean floor when they died. An equally exotic but feasible plan was to trap CO2 being emitted from the furnaces of coal burning facilities, compress the gas to turn the CO2 into a liquid, and pump the liquid deep in the earth or to the bottom of the ocean (an undersea experiment was actually done in 1999, and research on the technique is ongoing as of 2007 in countries including Japan and the United States).
In 2006, scientists proposed that the increased temperature of the atmosphere that has occurred over the past 150 years could be reversed by pumping tiny particles into the upper atmosphere to deflect the sun's rays away from Earth. In this scheme, the particles would be pumped from Earth's surface to the atmosphere via a hose, 15.5-mi (25-km) in length, held aloft by a blimp. However, once begun, the process could never be stopped, since the rebounded warming of the atmosphere could increase global temperatures by almost 10°F (6°C) each decade. Within a half century, life on Earth would be threatened. Understandably, the project is controversial.
Impacts and Issues
WORDS TO KNOW
CLIMATOLOGICAL WARFARE: Speculative use of deliberately engineered climate or weather changes as weapons of war: studied intensively in the United States from 1945 to the 1970s, after which such research was abandoned.
CLOUD SEEDING: The introduction of particles of (usually) dry ice or silver iodide with the hope of increasing precipitation from the cloud.
WATER VAPOR: The most abundant greenhouse gas, it is the water present in the atmosphere in gaseous form. Water vapor is an important part of the natural greenhouse effect. Although humans are not significantly increasing its concentration, it contributes to the enhanced greenhouse effect because the warming influence of greenhouse gases leads to a positive water vapor feedback. In addition to its role as a natural greenhouse gas, water vapor plays an important role in regulating the temperature of the planet because clouds form when excess water vapor in the atmosphere condenses to form ice and water droplets and precipitation.
IN CONTEXT: GEO-ENGINEERING OPTIONS
“Geo-engineering options, such as ocean fertilization to remove [CO2] directly from the atmosphere, or blocking sunlight by bringing material into the upper atmosphere, remain largely speculative and unproven, and with the risk of unknown side-effects. Reliable cost estimates for these options have not been published (medium agreement, limited evidence).”
[Editor's note: The assessment of certainty “(medium agreement, limited evidence)” is according to the IPCC, “based on the expert judgment of the authors on the level of concurrence in the literature on a particular finding (level of agreement), and the number and quality of independent sources qualifying under the IPCC rules upon which the finding is based.]
SOURCE: Metz, B., et al, eds. Climate Change 2007: Mitigation of Climate Change: Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press, 2007.
As the aforementioned example illustrates, the deliberate manipulation of the atmosphere is a very contentious issue. The climate engineering actions of one nation could affect all nations. Whether a nation has the legal or moral right to alter climate is questionable, especially since the precise details of how the atmosphere functions are still not clear. An action intended to change one aspect of the atmosphere could have other, unforeseen impacts or, in the case of the pumping of particles into the atmosphere courtesy of a blimp-supported hose, very undesirable known impacts.
Another aspect of climate engineering concerns the reason for the action. History shows that climate engineering has been contemplated for economic or military reasons rather than humanitarian. Whether a climate engineering strategy for global warming would be done for the common good or just to benefit a select group is unknown.
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Lovelock, James. The Revenge of Gaia: Earth's Climate Crisis and the Fate of Humanity. New York: Perseus Books, 2007.
Flemming, James R. “The Climate Engineers.” The Wilson Quarterly (Spring 2007).
Kirby, Alex. “Blue-Sky Thinking about Climate.” BBC News, January 7, 2004. < http://news.bbc.co.uk/2/hi/science/nature/3370211.stm> (accessed November 14, 2007).
Smalley, Eric. “Climate Engineering Is Doable, as Long as We Never Stop.” Wired, July 25, 2007. < http://www.wired.com/science/planetearth/news/2007/07/geoengineering> (accessed November 14, 2007).