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What is Solar Geoengineering?

Solar geoengineering is a proposed methodology to reflect sunlight back into space as a way to combat global warmin

Solar geoengineering is a proposed methodology to reflect sunlight back into space as a way to combat global warming. Solar geoengineering is also called solar radiation modification or management (SRM) and is a type of climate engineering. The hope is that solar geoengineering can prevent some, or all, of the damaging effects of climate change. But it is not without risk and uncertainties

How Solar Geoengineering Works

The purpose of solar geoengineering technologies is to cool the earth by reflecting sunlight back into space. It has long been known that any location is typically 15 degrees warmer in direct sun than in the shade. Solar geoengineering seeks to deflect the sun, creating an automatic cooling effect on earth. 


Solar radiation management, just as the name implies, is human management of the solar radiation that reaches earth. There are two main approaches currently being considered by scientists: stratospheric aerosol injection (SAI) and marine cloud brightening (MCB).

Stratospheric Aerosol Injection (SAI) 

SAI involves injecting tiny reflective particles, called aerosols, into earth’s upper atmosphere — the stratosphere. This would be done through an airplane delivery method, and various substances have been proposed, most notably sulfur and calcite. 

The theory is that since these particles will reflect sunlight back into space, it will have an immediate cooling effect on the planet. It mimics a natural process — volcanic eruption — creating a sense of security. It is seen as less manipulative, and is not considered tampering with nature. However, it will have climatic and precipitation effects globally. 

Proponents say that the advantages of SAI are that at moderate intensity it can combat most climate-related temperature and precipitation changes. It takes effect immediately, the direct climate effects are reversible, and it mimics a natural process. In addition, the implementation cost is low, it is technologically feasible, and scalable. 

While SAI is the most highly researched solar geoengineering theory, imperfect application could lead to unpredictable results. This, along with lack of thorough trials and research has caused many concerned scientists to urge further research to avoid “unacceptably high environmental, social, and geopolitical risks”.

Marine Cloud Brightening (MCB)

MCB involves spraying sea salt into low-lying marine clouds, thus “brightening” them. Increasing their brightness and reflectivity will allow them to reflect more of the sun’s rays away from earth. A secondary aim would be to extend the lifetime of the marine clouds, thereby enhancing the efficacy of MCB

MCB also remains an untested solar geoengineering theory. While it has the potential to work on a regional level, there are significant risks to large scale effects on weather and climate patterns. 

The other obstacles to MCB are the prohibitively high cost and limited application. MCB will only work in limited areas where the right type of clouds exists. This is currently estimated to be about 10% of the earth’s surface. 

Like SAI and other solar geoengineering technologies, MCB carries significant risks for not only the climate and environment but for societies worldwide. For this reason, concerned scientists are urging further research, transparency, and oversight. 

Advantages of Solar Geoengineering 

Solar geoengineering has the potential to combat the disastrous effects of climate change. While it does not address the root cause of climate change, which is related to greenhouse gas emissions, it provides a bridge in case the world cannot reach climate targets through emission reductions. 


Even as critical steps are taken to slow climate change, failure to reach essential targets will result in disastrous climate consequences for public health, food security, housing, and global water supply. The Paris Climate Agreement required the US and other nations to bring their net CO2 emissions to zero by mid-century in order to keep the global climate 2° or less below pre industrial levels.

Because this is a highly ambitious goal that will require significant changes, climate scientists are looking at ways to mitigate global warming and adapt solutions of prevention. Solar geoengineering is one of the best proposed methodologies to date in terms of research, ease of application, cost, and long-term climate impact. 

Disadvantages of Solar Geoengineering 

The disadvantages of solar geoengineering are all based on uncertainties and risks. While computer modeling has been used to test effects, the exact effect remains unknown without direct experimentation. The global effect cannot be effectively tested before application.


There is also the moral risk that solar geoengineering is used as an excuse to avoid reduction of greenhouse gas emissions — a sort of environmental crutch. 

Further Steps

In order for solar geoengineering to move forward, it is necessary to have mechanisms for oversight, transparent rules for conducting research, and means to involve the public in decision-making over outdoor experimentation. While solar geoengineering has potential, it should be seen more as an emergency intervention than a long-term climate solution. 

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