The Technologies to Change The Climate

Geoengineering refers to the intentional, large-scale technological manipulation of the Earth's climate system to counteract the effects of climate change (Parson & Keith, 2024). These technologies are generally grouped into two major categories:

​1. Solar Radiation Management (SRM)

​SRM technologies are designed to reflect a small fraction of the sun's energy back into space to cool the planet and offset the warming effect of greenhouse gases. These interventions do not remove carbon dioxide from the atmosphere, but rather mask the warming caused by it (Jinnah et al., 2019).

Technology	Mechanism
Stratospheric Aerosol Injection (SAI)	Injects tiny reflective particles (like sulfate aerosols or calcium carbonate) into the stratosphere. This mimics the cooling effect seen after large volcanic eruptions, where ejected ash and sulfur dioxide temporarily cool the Earth (Parson & Keith, 2024).
Marine Cloud Brightening (MCB)	Sprays fine particles of sea salt or other substances into low-lying marine clouds to make them whiter, which increases their reflectivity (or albedo), causing them to reflect more sunlight back into space (Jinnah et al., 2019).
Cirrus Cloud Thinning	Aims to reduce the number of high-altitude cirrus clouds. These clouds trap heat escaping from the Earth (long-wave radiation), so thinning them could allow more heat to escape to space, resulting in a cooling effect (Parson & Keith, 2024).

2. Carbon Dioxide Removal (CDR)

​CDR technologies are designed to actively pull carbon dioxide (\text{CO}_2) out of the atmosphere and store it durably in geological, terrestrial, or ocean reservoirs. Unlike SRM, these methods address the root cause of climate change by reducing the concentration of greenhouse gases (Abegg et al., 2024; Nordahl et al., 2024).

Technology	Mechanism
Direct Air Carbon Capture and Storage (DACCS)	Chemical plants or huge industrial facilities use chemical processes (liquid solvents or solid sorbents) to capture \text{CO}_2 directly from ambient air. The captured \text{CO}_2 is then compressed and stored permanently in deep underground geological formations (Abegg et al., 2024).
Bioenergy with Carbon Capture and Storage (BECCS)	This process involves growing biomass (like energy crops), burning it for energy (electricity or heat), and then capturing the \text{CO}_2 emissions released during combustion and storing them underground (Abegg et al., 2024).
Enhanced Weathering	Spreading finely ground, naturally occurring silicate or carbonate rocks over large areas of land or the ocean. These minerals react chemically with \text{CO}_2 in the atmosphere or water to form stable carbonate solids, effectively locking the carbon away (Abegg et al., 2024).
Nature-Based Solutions (e.g., Afforestation/Reforestation, Biochar)	Planting trees absorbs \text{CO}_2 as the trees grow. Biochar is another method, where organic waste is heated in the absence of oxygen, creating a stable charcoal that is added to soil, locking away the carbon (Abegg et al., 2024).

References

​Abegg, M., Clulow, Z., Nava, L., & Reiner, D. M. (2024). Expert insights into future trajectories: assessing cost reductions and scalability of carbon dioxide removal technologies. Frontiers in Climate, 6.

Jinnah, S., Nicholson, S., Morrow, D. R., Dove, Z., Wapner, P., Valdivia, W., Thiele, L. P., McKinnon, C., Light, A., Lahsen, M., Kashwan, P., Gupta, A., Gillespie, A., Falk, R., Conca, K., Chong, D., & Chhetri, N. (2019). Governing climate engineering: A proposal for immediate governance of solar radiation management. Sustainability, 11(14), 3954.

Nordahl, S. L., Hanes, R. J., Mayfield, K. K., Myers, C., Baker, S. E., & Scown, C. D. (2024). Carbon accounting for carbon dioxide removal. One Earth, 7(10), 1494–1500.

Parson, E. A., & Keith, D. W. (2024). Solar geoengineering: History, methods, governance, prospects. Annual Review of Environment and Resources, 49, 337–366.