General concept
History
The concept of the construction of space mirrors as a method of climate engineering dates back to the 1980s. The first proposals were suggested to cool Venus’ climate to provide for a theoretical future where humans occupy other planets. In 1989, James Early, working at the Lawrence Livermore National Laboratory, proposed using a "space shade" in diameter orbiting at Lagrangian Point L1. He estimated the cost at between one and ten trillion US dollars and suggested manufacturing it on the moon using moon rock. Space mirrors were also proposed at the "Response Options to Rapid or Severe Climate Change" round-table meeting organized by the President's Climate Change Technology Program in September 2001.Purpose
Space mirrors are designed either to increase or decrease the amount of energy that reaches a planet from the sun with the goal of changing the impact of UV radiation; or, to reflect light onto or deflect light off of a planet in order to change the sun’s lighting conditions. Space mirrors are an example of Solar Radiation Management (SRM), which is a "theoretical approach to reducing some of the impacts of climate change by reflecting a small amount of inbound sunlight back out into space." The concept is to reflect enough sunlight to reduce the Earth's temperature therefore balancing out the warming effect of greenhouse gases.Climate engineering
Most past proposals for the development of space mirrors are specifically to slow the progression of climate change on Earth. Deflecting a small amount of the sun’s energy from the Earth’s atmosphere would reduce the amount of energy entering the ecosystem of the Earth.Sunlight reflection/deflection
Some proposals for the development of space mirrors also focus on the ability to change localized lighting conditions on the surface of the Earth by shading certain sections or reflecting sunlight onto small sections. Doing this could allow for differentiated climates in local areas and potentially additional sunlight for enhanced crop growth. Past proposals and implementations for sunlight reflection have mainly been made by Russian space agencies.Debate
Climate experts have cautioned that geoengineering proposals like space mirrors, while potentially being able to cool the planet, would not provide any benefit for other climate related problems like high acidity levels in the ocean due to the build up of carbon. In the past, many scientists have also resisted the idea of using geoengineering to curb climate change, as the risks of causing adverse effects were too great and they worried it would encourage people to continue to use fossil fuels that contribute to that change.Policy
At times, politicians have been more eager to discuss climate engineering and space mirror proposals than scientists have been to think about implementing them. Politicians in the administrations of George W. Bush and Barack Obama have discussed and proposed funding for US-based space mirrors proposals. Scientists, however, are still worried about the significant risks. Matthew Watson, of the University of Bristol, led a £5m research study into the potential adverse effects of climate engineering and said, "We are sleepwalking to a disaster with climate change. Cutting emissions is undoubtedly the thing we should be focusing on but it seems to be failing. Although geoengineering is terrifying to many people, and I include myself in this, ts feasibility and safetyare questions that have to be answered". University of Oxford Professor Steve Rayner is also worried about the adverse effects of climate engineering, especially the potential for people to be too positive about the effects and stop trying to slow the actual problem of climate change. Though, he says there is a potential reason to doing climate engineering: "People decry doing limate engineeringas a band aid, but band aids are useful when you are healing".Russian implementation
The Znamya project was a series of orbital mirror experiments in the 1990s that intended to beamScientific theory
Geoengineering and climate change
Geoengineering research efforts to mitigate or reverse the changes to the Earth’s climate can be separated into two different categories,Research and development proposals
There have been several theoretical proposals for space mirrors since the 1980s as researchers attempted to discover a feasible way to partially reflect sunlight and slow down the warming of the Earth’s atmosphere using space mirrors. Research into space mirrors first began in 1989 by engineer James Early, who proposed a 2,000 km glass shield. The glass shield would need to be constructed on the Moon using moon rock due to its sheer mass. Lowell Wood, a researcher at the Lawrence Livermore National Laboratory, proposed sending a single, massive mirror into orbit at Lagrange point L1, approximately one million miles away from Earth. While orbiting at the Lagrange point 1, the space mirror would be able to remain in orbit without any additional energy supplies and continue to block sunlight. In 2006, Roger Angel, a researcher at the University of Arizona, proposed sending millions of smaller space mirrors as opposed to one large mirror to reduce costs and increase feasibility as a single mirror would need to be approximately 600,000 square miles to block just one percent of sunlight. Star Technology and Research looked to create a system of space mirrors which both blocked sunlight from reaching Earth and provided another source of clean energy for Earth. The company proposed launching several hundred space mirror spacecraft into orbit closer to Earth. These spacecraft would orbit around the Earth’s equator and could be remotely controlled to steer around Earth while covered with space mirrors that reflect sunlight. Additionally, the spacecraft would be equipped with solar panels which could collect some of the sunlight as well and send the captured energy back to be used back down on Earth.Development
Challenges
Since the successful launch of theDeployment logistics
The deployment and maintenance of a fleet of small space mirrors that can create a shade of around 100,000 kilometers in space would include necessary factors such as energy, construction, transportation, and ground support operations. Overall, the estimated cost of constructing and sending a fleet of space mirrors to space is around 750 billion dollars. If the space mirrors are able to achieve a 50-year lifetime, the annual maintenance cost estimates to around 100 billion dollars. Furthermore, if any individual satellite needed to be replaced at the end of their lifetime, the costs of the entire operation would amount to 5 trillion dollars. The deployment of either one large space mirror or a fleet of smaller mirror will also have to take into consideration of the millions of space debris within the Earth’s orbit. Most debris is small, weighing around 1 gram. However, depending on their speed, such debris can be catastrophic for satellites if they were to collide. Therefore, orbital satellites would need to maneuver out of the path of tracked space debris from the space mirror. Additionally, if one very large space mirror were to be deployed, its massive surface area will be a very large target for space debris. Therefore, maneuvering hundreds of space mirrors or one very large space mirror will prove to be very difficult due to the space debris and the potential size of the space mirror.Unintended climate change
The direct reflection of solar radiation away from the Earth may have certain adverse effects on the climate. As the Earth is exposed to less solar radiation, the planet will cool down, but this might result in unpredictable weather patterns. An overall drop in global temperature may affect the hydrological cycle and could increase the intensity of droughts and floods. Furthermore, the change of temperature and climate may also negatively impact the cultivation of crops. As a result, the reflection of solar radiation could adversely affect around 65% of the global population.See also
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