Atmospheric Geoengineering Experiment to Curb Global Warming

• 24 Nov 2018

The research by scientists at Harvard and Yale universities, published in the journal Environmental Research Letters, proposed using a technique known as stratospheric aerosol injection, which could cut the rate of global warming in half.

• The technique would involve spraying large amounts of sulfate particles into the Earth's lower stratosphere at altitudes as high as 12 mile (around 20 kilometre). The sulfates will be delivered with specially designed high-altitude aircraft, balloons or large naval-style guns.
• The idea is to help shield the Earth from just enough sunlight to help keep temperatures low, i.e. increasing the planet’s albedo, or reflective power. This method would mimic what large volcanoes do. E.g.:
  • In 1991, Mount Pinatubo erupted in the Philippines. It was the second largest eruption of the 20th century. In total, the eruption injected 20 million tons of sulfur dioxide aerosols into the stratosphere which lowered atmospheric temperature by approximately 1-degree Fahrenheit. However, it’s effect only lasted a couple of years because the sulfates eventually fell to Earth. Moreover, it affected precipitation in many parts of the world.
• The report does, however, acknowledge that the technique is purely hypothetical and would involve developing a new, purpose built tanker with substantial payload capabilities that may take around 15 years' of time.

Geoengineering

• Geoengineering is the technique designed to tackle the effects of climate change directly, usually by removing carbon dioxide (CO₂) from the air or limiting the amount of sunlight reaching the planet's surface.
• It involves deliberate planet-scale interventions to counteract global warming.
• Methods to remove CO₂ from the air: Increasing the capacity of trees and plants to absorb CO₂ from the air, burning large quantities of wood in power plants with carbon-capture technology, making and burying large amounts of charcoal to lock carbon into the soils, grazing cattle in a way designed to turn grasslands into giant carbon sinks, fertilising the oceans with iron to encourage the growth of algae that can soak up atmospheric carbon dioxide, etc.
• Methods to limit amount of sunlight: Placing mirrors in space that reflect sunlight away from the Earth, firing sulphate aerosols into the stratosphere, using unmanned ships to increase above-ocean cloud cover by spraying sea water into the air, etc.

Concerns

• The technique could result in reduced precipitation, soil moisture and river flow in many regions.
• Injection of sulphur compounds into the stratosphere is likely to increase acid deposition on the ground and also contribute to ozone layer depletion.
• Once the aerosol has been injected into the atmosphere, it cannot be removed.
• Stratospheric aerosol injection techniques could jeopardize crop yields, lead to droughts or cause extreme weather.
• The proposals also don't address the issue of rising greenhouse gas emissions, which are a leading cause of global warming. Few argue that it's only a temporary Band-Aid covering a problem.
• Solar radiation management is still a much worse solution than greenhouse gas emissions: it is more costly and much more risky over the long run.
• There are the ethical and governance issues that surround geoengineering as well, questions about who should be allowed to do what and when.

Conclusion

• The buildup of greenhouse gases is already altering the atmosphere and climate in an unprecedented and uncontrolled manner. Climate researchers should explore solar geoengineering to determine whether it would actually work and how safe it would be.
• Along with this political scientists also need to start thinking about how to implement such an unprecedented planetary project. All that will be left then is for society and governments to face the impossibly difficult task of deciding whether to do it.