Research press release





今回、Jonathan Proctorたちは、1982年に起こった2つの大規模な火山事象(メキシコのエルチチョン火山の噴火とフィリピンのピナトゥボ山の噴火)の影響を調べた。いずれの火山事象においても多量の硫酸塩エアロゾルの前駆体が成層圏に注入されており、これが最初に成層圏ベールを発想する上で役立った。Proctorたちは、エアロゾル濃度、日照データ、および作物収量の記録を調べて、太陽光が反射して宇宙空間に散乱する量が増えると、C3作物(低温で湿潤な気候で光合成の効率が高くなるイネ、ダイズ、コムギなど)とC4作物(高温で晴天に恵まれた気候で光合成の効率が高くなるトウモロコシなど)の収量に悪影響が及ぶことを明らかにした。


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.

doi: 10.1038/s41586-018-0417-3

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