IB Environmental systems and societies 6.3E Geoengineering Notes

Geoengineering: Treating the Symptoms of Climate Change, Not the Cause

1. Geoengineering is the deliberate, large-scale intervention in Earth's climate system.
2. It aims to reduce the impacts of climate change, but it treats the symptoms, not the root cause of rising greenhouse gas emissions.
3. Solar Radiation Management (SRM) reflects sunlight away from Earth to cool the surface.
   1. SRM methods include stratospheric aerosol injection, space mirrors, and marine cloud brightening.
4. Carbon Dioxide Removal (CDR) removes CO₂ directly from the atmosphere.
   1. CDR methods include ocean fertilization, direct air capture, BECCS, biochar, and enhanced weathering.
5. All options involve high uncertainty about their side effects.
6. All options carry high costs and rely on limited real-world trials.
7. All options raise strong governance and geopolitical questions about who decides to deploy them.

Solar Radiation Management: Reflecting Sunlight to Cool the Planet

1. Stratospheric Aerosol Injection (SAI)
   1. Reflective sulfate aerosols are released into the stratosphere, mimicking a volcanic eruption.
   2. The aerosols scatter sunlight back into space, lowering surface temperatures.
   3. They are delivered by aircraft, balloons, or artillery.
   4. Cooling potential is high, but the effect is temporary, lasting roughly 1 to 3 years per injection.
   5. It can reduce rainfall and raise regional drought risk, threatening agriculture.
   6. It has uncertain effects on monsoons and ozone chemistry.

The Sunshade Analogy for SAI

Two More SRM Methods: Space Mirrors and Marine Cloud Brightening

1. Space Mirrors and Solar Shields
   1. Large mirrors placed in space block or deflect sunlight before it reaches Earth.
   2. Cutting solar input by even a small percentage would produce global cooling.