Extreme science - Solar geoengineering

Can solar geoengineering help reverse climate change?

 Extreme science - Solar geoengineering

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• The story: Climate science requires experts to take observations from high orbit, in the ocean depths and all sorts of places in between, as well as models which stretch the powers of the most super supercomputers. And even with the best of data, it is quite tough for climate scientists to be exact about their predictions.
• Solar geoengineering: Solar geoengineering is a term used to describe a group of hypothetical technologies that could, in theory, counteract temperature rise by reflecting more sunlight away from the Earth’s surface. It is an emerging field of thinking - which the IPCC refers to as “solar-radiation modification”. The body of the new 2021 report agrees, finding that research has consistently shown such methods “could offset some of the effects of increasing greenhouse gases on global and regional climate, including the carbon and water cycles”.
• A big ray of hope: Many climate scientists believe that talk of solar geoengineering is a siren call that could lure policymakers away from the course of greenhouse-gas cuts while not, in the end, doing any good. That may dash the whole planet on to the rocks.

1. Whether achieved through particles in the stratosphere, brightened maritime clouds or some other means, solar geoengineering would not be a simple reversal of greenhouse warming; it is a form of deliberate climate change with its own potentially dangerous side-effects.
2. Its impacts on atmospheric chemistry and circulation are not well understood. An approach which suited one country might be bad for another.

• Technical details: There are several proposed solar geoengineering technologies. These include marine cloud brightening, cirrus cloud thinning, space-based techniques, and stratospheric aerosol scattering, amongst others.

1. Marine cloud brightening would attempt to brighten marine clouds to reflect more sunlight back into space.
2. Cirrus cloud thinning would attempt to reduce the thin, high-altitude cirrus clouds to emit more long-wave radiation from the earth to space.
3. Space-based technologies would attempt to reflect a small fraction of sunlight away from the earth by positioning sun shields in space.
4. Stratospheric aerosol scattering would introduce tiny reflective particles, such as sulfate aerosols or perhaps calcium carbonate, into the upper atmosphere, where they could scatter a small fraction of sunlight back into space.

• Limitations: All types of solar geoengineering – known also as solar radiation management (SRM) – are united by their goal of limiting the effect of sunlight on the Earth, but they vary widely in their approach. Possible methods include reducing heat-trapping clouds, sending a giant sunshade up into orbit or releasing aerosols into the stratosphere. Although these technologies could theoretically lower global warming, they do not aim to reduce the amount of greenhouse gases in the atmosphere and, therefore, would not be able to directly address problems such as ocean acidification.
• One sure benefit: Research shows that using solar geoengineering could indirectly lower the amount of CO2 in the atmosphere by stemming permafrost melt, reducing energy-sector emissions and causing changes to the carbon-cycle feedback.
• Summary: Climate models have consistently shown that solar geoengineering, when used in moderation and combined with emissions cuts, has the potential to reduce climate changes around the globe. For example, it could reduce climate impacts such as extreme temperatures, changes in water availability, and intensity of tropical storms.

 

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