【地球工学】火山噴火から着想を得た成層圏を覆い隠す試みは農業に悪影響を及ぼす

Injecting aerosols into the stratosphere to counter climate change could do as much damage to crop yields as it would protect them from rising temperatures, reports a paper published in this week’s Nature.

Stratospheric veils are a geoengineering concept in which aerosols would be artificially injected into the stratosphere to help reduce the amount of sunlight reaching the Earth, countering the effects of climate change. It has been suggested that this solar radiation management technique would benefit agriculture by reducing the heat stress to crops and thereby increasing yields.

Jonathan Proctor and colleagues studied the aftermath of two major volcanic events - the 1982 eruption of El Chichon in Mexico and the explosion of Mount Pinatubo in the Philippines. Both events saw considerable quantities of sulfate aerosol precursors thrust into the stratosphere, and helped inspire the veil concept in the first place. They analyzed aerosol levels, solar irradiation data and recorded crop yields, and find 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.)

The authors also model the Earth system, and show 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. As such, they conclude that geoengineering efforts based on stratospheric aerosols would fail to mitigate the threat that climate change poses to global agriculture and food security.