6.3.11 (HL)—Geoengineering

Geoengineering is deliberate large-scale intervention in Earth's climate system. Some methods alter incoming radiation and treat warming symptoms; others remove carbon dioxide and address part of the cause.

Approach	Examples	What remains unresolved
Solar-radiation intervention	space mirrors, stratospheric aerosols, brighter clouds	atmospheric CO2 and ocean acidification remain; rainfall and termination risks
Carbon removal	ocean fertilization, BECCS, direct air capture, biomass carbon storage	permanence, land/energy demand, ecological effects and monitoring

Compare mechanism, speed, permanence, high cost, uncertain impacts, limited trials, political consent and geopolitical conflict. Fast cooling is not the same as solving the cause.

Reflecting sunlight could lower temperature while ocean acidification continues; durable CO2 removal tackles both forcing and acidification more directly but is constrained.

Geoengineering is not a proven substitute for reducing emissions; potential benefit and system-wide risk must both be evaluated.