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How does geoengineering aim to influence Earth’s climate?

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Illustration of various geoengineering techniques to address climate change, including carbon capture and storage methods like artificial trees, industrial scrubbers, and deep ocean CO2 storage, as well as solar reflectance strategies such as sulfur aerosols, reflective crops, cloud whitening, and orbital mirrors. The scene shows these interventions applied to land, sea, and atmosphere, with labeled features explaining each process. — Geoengineering Various geoengineering proposals designed to increase solar reflectance or capture and store carbon.

Geoengineering refers to the large-scale, intentional manipulation of Earth’s climate processes to achieve a specific benefit, such as mitigating global warming. Because these interventions involve modifying complex global systems that are not yet fully understood, they carry inherent risks and remain a subject of significant scientific and ethical debate.12

Proposals to influence the climate generally fall into two distinct categories:

Increasing Solar Reflectance

These methods aim to reduce the heating effect of sunlight by increasing the amount of solar radiation reflected back into space. By altering Earth’s heat budget, these techniques could potentially offset rising temperatures, though they do not address the underlying concentration of greenhouse gases. Proposed techniques include:1
* Stratospheric sulfur injection: Creating an aerosol layer of sulfur in the stratosphere to scatter incoming sunlight, mimicking the cooling effects observed after major volcanic eruptions.34
* Surface and cloud modification: Increasing ground-level albedo, whitening marine clouds, or deploying orbital sunshades to reflect solar energy.4

Carbon Removal

These approaches seek to address the root cause of global warming by extracting carbon dioxide (CO₂) from the atmosphere and storing it elsewhere. This is considered more comprehensive as it could counteract both rising temperatures and ocean acidification. Methods include:1
* Biological and artificial sequestration: Techniques such as ocean fertilization to promote phytoplankton growth, biochar production, and the use of "artificial trees" or scrubbing towers to capture CO₂.56

Rigorous evaluation and testing are essential before any such schemes are implemented to avoid unintended ecological consequences.1