Chapter 01 · Climate & transitionClimate & Greenhouse Gas Emissions
Climate engineering / geoengineering
Definition
The deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change (Royal Society, 2009). Two distinct families are conventionally grouped under the term: carbon dioxide removal (CDR), which lowers atmospheric CO₂ (afforestation, direct air capture, enhanced weathering, ocean alkalinity), and solar radiation modification (SRM), which reflects sunlight to cool the planet without addressing CO₂ levels (stratospheric aerosol injection, marine cloud brightening, cirrus cloud thinning).
References
Canonical definition; CDR vs SRM categories with divergent risk profiles; governance recommendations.
Technique inventory (SAI, MCB, cirrus cloud thinning, ocean methods); CCT's limited research status; solar geoengineering scope.
Overview
What it means
The Royal Society's landmark framing still organises the debate: CDR addresses the root cause but works slowly and is now treated as a mitigation complement embedded in net-zero pathways; SRM could cool quickly but masks rather than fixes the problem — it does nothing for ocean acidification, risks termination shock if stopped, alters regional weather with uneven winners and losers, and raises unresolved governance questions (who may deploy, who is liable for side effects).
Cirrus cloud thinning — seeding high ice clouds to let more heat escape to space — is among the less-researched SRM proposals, with uncertain feasibility. Critics (CIEL and others) argue speculative geoengineering risks delaying emissions cuts — the "moral hazard" objection — and note that unilateral deployment incentives grow as impacts worsen.
Governance remains thin: research moratoria debates under the CBD and London Protocol touch some techniques; no comprehensive international regime exists.
How it is used
IPCC scenarios embed CDR at scale while excluding SRM from policy baselines; governments fund research programmes and, in some jurisdictions, restrict outdoor experiments; the term anchors debates on climate emergency "break-glass" options and solar-geoengineering governance proposals.
Why it matters
Geoengineering frames the hardest question in climate policy — whether societies should (or can governably) manipulate the climate system itself if mitigation falls short.