Last updated August 9, 2018 at 9:10 am
Scientists go back to the volcanic source to raise questions about solar radiation management technique.
A veil of stratospheric sulfate aerosols circles the Earth in the months following the 1991 eruption of Mount Pinatubo. Credit: Jonathan Proctor and Solomon Hsiang.
US scientists have questioned the potential of “stratospheric veils” to counter climate change after having a more detailed look at the incidents that inspired the idea in the first place.
They now believe that injecting aerosols into the stratosphere could do as much to damage crop yields as it would to protect them from rising temperatures.
A team led by Jonathan Proctor from the University of California, Berkeley, investigated the aftermath of two major volcanic eruptions: El Chichón in Mexico in 1982 and Mount Pinatubo in the Philippines in 1991.
Both events saw considerable quantities of sulfate aerosol precursors thrust into the stratosphere, seeding the idea for a new solar radiation management technique that would benefit agriculture by reducing the heat stress to crops, thereby increasing yields.
Negative effect on yields
However, when Proctor and colleagues analysed aerosol levels, solar irradiation data and recorded crop yields they found that the increased scattering of sunlight back into space had a negative effect on the yields of both C3 crops (such as rice, soy or wheat, which photosynthesize more efficiently in hot, sunny climates) and C4 crops (including maize, which is more efficient in cool, wet climates).
They also modelled the Earth system and found that under a global stratospheric veil the beneficial effect to crop yields from the resultant cooling would be essentially negated by the loss in crops due to the reduction in sunlight.
“Applying our yield model to a solar radiation management scenario based on stratospheric sulfate aerosols, we find that projected mid-twenty-first century damages due to scattering sunlight caused by solar radiation management are roughly equal in magnitude to benefits from cooling,” they write in a paper published in Nature.
“This suggests that solar radiation management – if deployed using stratospheric sulfate aerosols similar to those emitted by the volcanic eruptions it seeks to mimic – would, on net, attenuate little of the global agricultural damage from climate change.
“Our approach could be extended to study the effects of solar radiation management on other global systems, such as human health or ecosystem function.”
