Geoengineering method found wanting


A proposal to reflect away incoming solar radiation may result in food supply disasters. Andrew Masterson reports.


The eruption of Mt Pinatubo provided scientists with a model by which to study the effects of a proposed geoengineering project.
The eruption of Mt Pinatubo provided scientists with a model by which to study the effects of a proposed geoengineering project.
Philippe Bourseiller / Getty Images

Proponents of geoengineering as a way to mitigate the effects of global warming have been dealt a blow, with a study in the journal Nature concluding that one of the most favoured methods will do more harm than good.

The widespread use of stratospheric aerosols has been seen as perhaps the most promising geoengineering prospect. In a journal editorial published in 2016 a team of atmospheric scientists called it “arguably the best understood (practical) geoengineering method” available, and recommended a lot more research to better model its effects.

In principle, the approach is simple and elegant. The idea is to release trillions and trillions of tiny airborne bubbles made of sulfate into the upper atmosphere. The result would be an effective reflector shield, bouncing back a significant portion of incoming solar radiation, thereby reducing its heating effect on Earth.

To better model this, a team led by Jonathan Proctor of the University of California, Berkeley, in the US, turned to real life events – namely the 1982 eruption of the El Chichón volcano in Mexico and the 1991 explosion of Mount Pinatubo in the Philippines.

Both eruptions spewed vast amounts of sufate aerosol precursors into the air. Proctor and his colleagues gathered records and investigated the after-effects of the blasts, comparing aerosol levels with incoming solar radiation and crop yields in the affected areas.

What they found was troubling. The heavy aerosol shield resulted in less sunlight reaching farmland and produced a negative effect on a wide variety of crops, including maize, rice, soy and wheat.

Modelling the effects of a global aerosol geoengineering deployment, the researchers found that the projected damage to crop yields roughly balanced the estimated decline in temperatures.

One of the main expected benefits of large-scale geoengineering is ensuring the continued production of food crops. Proctor’s team found that stratospheric aerosols, far from bringing about such a result, significantly worsened the problem.

  1. https://www.nature.com/articles/s41586-018-0417-3
  2. https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016EF000418
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