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.
   3. It demands extreme precision, launch capacity, and energy.
   4. Costs are enormous, it is hard to maintain, and it has no real-world trials.
2. Marine Cloud Brightening
   1. Fine sea-salt particles are sprayed into low marine clouds to make them whiter and more reflective.
   2. It produces a short-term, regional cooling effect, mostly over oceans.
   3. So far only very limited small-scale field tests exist, such as trials over Australia's Great Barrier Reef around 2020.
   4. Risks include unpredictable rainfall and other regional atmospheric changes.

Carbon Dioxide Removal: Taking CO₂ Back Out of the Air

1. Ocean Fertilization
   1. Adding iron, nitrogen, or phosphorus stimulates phytoplankton growth.
   2. Phytoplankton absorb CO₂ during photosynthesis and later sink to the ocean floor.
   3. The oceans already store roughly 38,000 gigatonnes of carbon, making them a major long-term sink.
   4. Algal blooms from fertilization may disrupt ecosystems.
   5. Decaying blooms can create dead zones through oxygen depletion.
   6. The long-term stability of the stored carbon is uncertain.
2. Direct Air Capture (DAC)
   1. Machines capture CO₂ directly from ambient air.
   2. The captured CO₂ is stored underground or used industrially.
   3. It has a high energy demand and is currently very expensive.
   4. It remains promising because it can create negative emissions.
3. Bioenergy with Carbon Capture and Storage (BECCS)
   1. Biomass is grown, burned for energy, and the resulting CO₂ is captured and permanently stored.
   2. It produces energy while removing atmospheric CO₂.
   3. It needs large land areas, competing with agriculture and biodiversity.
4. Biochar
   1. Biomass is partially burned into charcoal and buried, locking carbon into soils.
   2. Soil fertility improves, but the climate impact depends on scale and land availability.
5. Enhanced Weathering
   1. Crushed silicate rock is spread over land or coasts to speed up its natural reaction with CO₂.
   2. The reaction locks carbon into stable carbonate minerals.
   3. It requires vast quantities of mined and crushed rock, which is energy-intensive.

Advantages: Why Geoengineering Is Even Considered

1. Some SRM methods offer rapid temperature reduction, useful in a climate emergency.
2. It provides a backup plan if emissions cuts fail or come too slowly.
3. It could protect vulnerable ecosystems, for example by slowing coral bleaching.
4. CDR methods can deliver long-term CO₂ removal if deployed at global scale.

Disadvantages and Risks: Why It Is No Substitute for Cutting Emissions

1. There is high scientific uncertainty about regional climate impacts.
2. SRM can trigger unintended consequences.
   1. Monsoons can be disrupted.
   2. Agriculture can fail in affected regions.
   3. Drought and flood cycles can intensify.
3. SRM does not reduce CO₂, so two problems continue.
   1. Ocean acidification continues because atmospheric CO₂ is unchanged.
   2. Warming rebounds rapidly if SRM stops, a danger known as termination shock.
4. Costs of development, deployment, and maintenance are high.
5. Political hesitancy and conflicting national interests slow any agreement.
6. There is a risk of geopolitical conflict if one nation alters the climate unilaterally.
7. Relying on geoengineering can weaken the will to cut emissions, a problem called moral hazard.

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