Geoengineering and Solar Radiation Management

In a recent article published in the journal Current Science Govindswamy Bala assesses the potential effectiveness of solar radiation management geoengineering and potential side effects. This brief article would provide an excellent overview of SRM approaches in a geongineering teaching module. Among the take-aways from the article:

  1. Because of the anticipated quick response of climate systems to reductions in sunlight, SRM deployment could be delayed until dangerous climate change was “imminent;”
  2. SRM would likely weaken the global water cycle by only offsetting temperature-related precipitation changes, i.e. enhanced atmospheric carbon dioxide under SRM deployment would suppress precipitation while solar forcing would have a much smaller impact on precipitation;
  3. Whereas the atmosphere would warm slowly with current projections of increased concentrations of greenhouse gases, a failure of SRM could visit commensurate warming on the globe in the course of only 10-20 years. Moreover sudden termination of an SRM approach could result in a release of carbon stored on land and in the ocean, triggering a positive feedback mechanism that would result in much greater and faster warming;
  4. A uniform reduction in solar radiation with SRM deployment could lead to reduce El Nino Southern Oscillation and increased North Atlantic overturning;
  5. Sulfate aerosol injection could cause a significant depletion of the ozone layer by accelerating hydroxyl-catalyzed ozone destruction cycles;
  6. Compared to a scenario of high GHG concentration and and no SRM geoengineering, SRM approaches deployed under high greenhouse gas concentrations scenarios could create a climate more similar to that with “natural” greenhouse gas concentrations than a scenario with high greenhouse gas concentrations and no SRM geoengineering.

This article would be ideal to tease out equity questions associated with geoengineering (for example, assuming that SRM would reduce the global impacts of climate change, would it be acceptable to deploy even if there were negative regional impacts?), as well as the implications associated with the potential failure of SRM technologies for inter-generational equity. The findings of Bala on water cycle issues could also be contrasted with research from others e.g. Caldeira who discount this potential impact; it would be a good opportunity to have students tease out differing scientific assumptions, e.g. the impacts of solar radiation suppression on surface runoff. Moreover, should we also factor in the potential regional precipitation declines associated with climate change?

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