1. Solar Radiation Management (SRM) Strategies
Stratospheric Aerosol Injection
Inspired by volcanic eruptions (e.g., Mount Pinatubo’s 0.5°C global cooling in 1991), this approach involves dispersing reflective particles like sulfuric acid or calcium carbonate at 20 km altitude. Key developments:
- SCoPEx Project: Harvard’s 2023 controlled balloon experiment released 2 kg of CaCO₃ in Sweden, showing 95% predicted reflectivity but raised ozone layer concerns.
- Modeling Outcomes: A 2023 Nature Climate Change study warns that equatorial SRM could reduce Sahel rainfall by 30%, threatening food security for 135 million people.
Marine Cloud Brightening
Enhancing cloud reflectivity by spraying seawater aerosols. The University of Washington’s 2022 MACE trial (Marine Atmospheric Cloud Experiment) demonstrated a 10% albedo increase over 500 km² using drone-dispersed 0.3µm particles. Challenges include salt crystallization consistency and regional climate disruption risks.
Space-Based Reflectors
Proposals like MIT’s 2023 “space bubbles” concept—inflatable SiO₂ shields at Lagrange points—could block 1.8% solar radiation. Estimated costs: $10 trillion over 30 years, with 0.1% annual maintenance leakage potentially catastrophic.
2. Carbon Dioxide Removal (CDR) Technologies
Direct Air Capture (DAC)
- Climeworks’ Orca Plant (Iceland): Captures 4,000 tons CO₂/year using amine filters, mineralizing it underground. Costs: 600/ton(2023),projectedtodropto600/ton(2023),projectedtodropto200/ton by 2030.
- U.S. Federal Support: 45Q tax credits now offer $180/ton for DAC storage, spurring 32 new projects in 2023.
Bioenergy with Carbon Capture (BECCS)
Drax Power Station (UK) combines biomass combustion with amine scrubbing, achieving 94% capture efficiency. However, a 2023 Science study found large-scale BECCS could require 40% of global cropland, threatening biodiversity.
Enhanced Weathering
Grinding silicate rocks (e.g., olivine) to accelerate CO₂ absorption. Project Vesta’s 2023 Caribbean trial spread 1,300 tons of olivine sand, capturing 370 tons CO₂ but causing a 15% pH drop in local waters, killing coral larvae.
3. Ocean-Based Interventions
Iron Fertilization
Adding iron to HNLC (High-Nutrient Low-Chlorophyll) oceans to boost phytoplankton blooms. The 2022 LOHAFEX II experiment triggered a 1,200 km² algal bloom capturing 6,000 tons CO₂, but 80% decomposed within weeks, releasing methane.
Artificial Upwelling
Using wave-powered pumps to bring nutrient-rich deep water to the surface. China’s 2023 South China Sea trial increased fish biomass by 25% but caused hypoxia at 200m depths.
Alkalinity Enhancement
Adding crushed limestone to oceans to counteract acidification. California’s 2023 pilot raised pH by 0.3 units along 10 km coastline but increased turbidity, reducing seagrass photosynthesis by 40%.
4. Governance and Ethical Challenges
The Moratorium Dilemma
The UN Convention on Biological Diversity’s 2022 non-binding SRM moratorium is challenged by:
- Private ventures: Make Sunsets’ 2023 unauthorized sulfur dioxide launches from Mexico.
- National interests: India’s draft National Geoengineering Policy (2024) reserves SRM as a heatwave emergency option.
Transboundary Impacts
Climate models show SRM in the Northern Hemisphere could:
- Delay monsoon onset in Asia by 18 days (Geophysical Research Letters, 2023).
- Increase Amazon drought frequency by 35% (Nature Communications, 2023).
Moral Hazard
A 2023 survey of 12,000 policymakers revealed 61% view geoengineering as a “distraction from emissions cuts,” with CDR funding increasing fossil fuel “bridging” rhetoric by 200% since 2020.
5. Emerging Innovations
Electrochemical CDR
UC Berkeley’s 2023 “battery” converts CO₂ into formate using copper catalysts, achieving 92% efficiency at $50/ton scalability.
Biochar Carbon Removal
Locking CO₂ in pyrolyzed plant matter. The 2023 EBC (European Biochar Certificate) market traded 200,000 tons credits, but lifecycle analyses show 20% net removal after transport emissions.
Cryosphere Preservation
- Arctic Ice Management: Proposals to pump seawater onto thinning ice to enhance reflectivity. 2023 MIT simulations show 0.2°C global cooling potential but require 8,000 wind-powered pumps at $500 billion/year.
- Glacier Geoengineering: Swiss PERMOS project’s 2023 reflective geotextile covers preserved 75% of Gurschen Glacier volume, yet costs $8/m² limit scalability.
6. Equity and Justice Considerations
Vulnerable Nations
The Alliance of Small Island States (AOSIS) 2023 resolution demands veto power over SRM deployment after studies showed 50% higher tropical storm risks with mid-latitude aerosol injection.
Indigenous Rights
A 2023 Harvard-NREL study found 83% of U.S. DAC projects are planned on Native lands without consultation, violating UNDRIP Article 29.
Intergenerational Ethics
Modeling shows SRM termination shock—if abruptly stopped—could cause 0.3°C/year warming, 10x faster than current rates (Earth’s Future, 2023), disproportionately burdening future generations.
Conclusion
Climate engineering technologies present a double-edged sword: potentially critical for limiting warming to 1.5°C yet fraught with ecological and geopolitical risks. As the IPCC’s 2023 AR7 report allocates 300 pages to CDR/SRM analysis—triple previous assessments—the coming decade demands rigorous international governance frameworks balancing innovation, equity, and precautionary principles. Whether humanity can responsibly “hack” the climate system remains an open question with civilizational stakes.
