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Solar geoengineering, also called solar radiation management, is a process of rapidly cooling the planet through a set of proposed methods to reflect sunlight. According to researchers, solar engineering has two main approaches: stratospheric aerosol injection and marine cloud brightening.
Stratospheric aerosol injection (SAI) involves the process of injecting micro-reflecting particles, referred to as aerosols, into the upper atmosphere to cool the Earth. Marine cloud brightening (MCB) involves the use of sea salt to stimulate cloud formation above the ocean- helping to reflect sunlight in the region.
The method and effect of SAI are similar to what occurs during large volcanic eruptions. When this happens, volcanoes emit tiny particles into the upper atmosphere, called the stratosphere. These tiny particles reflect sunlight and lead to cooling till they remain in the stratosphere- it could be up to a few years after volcanoes emit them.
SAI can copy the cooling effect of a large volcanic eruption’s effect on lower global temperatures by injecting aerosol particles into the stratosphere. If the approach of SAI is ever used, it would have a worldwide impact by decreasing global temperatures and changing precipitation patterns around the world.
The approach of MCB included spraying sea salt in low-lying marine clouds to increase their reflectivity and brightness to increase cooling in the region. Brighter clouds would help to decrease the amount of solar radiation that reaches the Earth’s surface. Thus, lowering atmospheric and ocean temperatures as they absorb less solar energy.
Experts have understood the benefits and risks of solar geoengineering through observational studies and computer modeling for many years.
If solar geoengineering does not address the main cause of climate change, which is greenhouse gas emissions, mostly from fossil fuel burning, nor does it limit ocean acidification and the dangerous effects on human and planetary health from the use of fossil fuel, then why study it?
Although world leaders and countries are taking steps and carrying out measures to tackle climate change, it may not be enough to reduce global warming to the levels needed to avoid severe climatic impacts. It is necessary to limit the global temperature increase to the Paris Agreement’s target of ‘below 0.2 degrees Celsius above pre-industrial levels and carry out actions to limit the temperature increase to 1.5 degrees Celsius.
For this, the United States and other countries need to bring net global carbon dioxide emissions to zero by mid-century, along with significant reductions in emissions of other greenhouse gases. However, it is possible that global actions may not suffice. The world would still face climate risks at 1.5 degrees Celsius.
While experts explore geoengineering approaches’ potential effectiveness and feasibility, adaptation and mitigation should always remain the first solution. Solar geoengineering has worldwide implications, so its consideration as a climate response needs effective international governance. Sound governance would have to be sustained for quite some time. Even temporary uses, such as deploying stratospheric aerosols to limit warming while the world reduces its emissions, would need to be sustained for more than half a century or less.
Solar geoengineering can be very problematic due to its risks and uncertainties. One of the risks is the ‘moral hazard’. According to this risk, there is a danger that technology might become an excuse to halt emissions reduction and slow down the process of shifting toward a low-carbon economy.
As mentioned before, it does not address the main cause of climate change- increasing emissions due to fossil fuel burning. Further, there is not much information available as to how solar engineering can affect regional weather patterns. Little information is known about how it could affect actions to control emissions and politics around the world.
Atmospheric experiments to assess technologies like solar engineering deserve timely public scrutiny and debate due to their ecological and ethical risks. Before testing solar engineering outdoors, it is essential that civil society and experts insist that governments put in place: rules for transparency in research, mechanisms to oversee the technology, and methods to involve the public in decision-making.
These discussions should have considerable leadership from countries and communities most vulnerable to climate change. They must be able to drive decision-making and research priorities.
The Union of Concerned Scientists (UCS) opposes solar geoengineering deployment due to its considerable ethical, geopolitical, and ecological risks and challenges. The UCS opposes any stratospheric tests of this technology at a scale that would significantly impact the planet’s surface climate.
According to the UCS, any small-scale stratospheric experiments should meet certain criteria- funding should come only from governments and entities that support adaptation and mitigation as the first solution to climate change.
In conclusion, there is a lot to understand about solar geoengineering. The UCS suggests a preventive method to examine potential climate response options, including understanding the risks and benefits of solar engineering to cool the planet by reflecting sunlight into space.