Keep Factually independent
Whether you agree or disagree with our analysis, these conversations matter for democracy. We don't take money from political groups - even a $5 donation helps us keep it that way.
What is geoengineering and its scientific basis?
Executive Summary
Geoengineering describes deliberate, large-scale interventions in Earth’s climate system divided into two scientifically distinct families: Carbon Dioxide Removal (CDR), which seeks to extract and store CO₂ from the atmosphere, and Solar Radiation Management (SRM), which aims to reduce incoming solar energy to cool the planet. The scientific basis for both rests on established climate physics—greenhouse gases trap longwave radiation and changing shortwave or longwave fluxes alters global temperature—but the viability, side-effects, costs, and governance implications remain highly uncertain and contested across recent analyses and institutional reviews [1] [2] [3].
1. The sharp split: Two rival technocratic approaches with very different promises and problems
Geoengineering is consistently framed in the literature as a bifurcated field: CDR and SRM, each anchored to different physical mechanisms and policy roles. CDR methods aim to remove atmospheric CO₂ and thereby reduce the radiative forcing that drives long‑term warming; examples include afforestation, bioenergy with carbon capture and storage, ocean-based approaches, and engineered direct air capture [3] [1]. SRM methods attempt rapid cooling by altering Earth’s shortwave budget—proposals include stratospheric aerosol injection and marine cloud brightening that increase albedo or reflectivity. The two approaches are not interchangeable: CDR addresses the root cause (elevated CO₂) and is potentially permanent but expensive and scale-limited, while SRM can produce faster, cheaper temperature reductions but does not remove CO₂, risks regional climate disruption, and requires continuous deployment [1] [4].
2. The physics is simple; the outcomes are not—models show promise and peril
The scientific basis rests on radiative balance: adding greenhouse gases traps outgoing longwave radiation, warming the climate; removing CO₂ or reducing incoming solar energy affects that balance and changes global mean temperature. Earth system models and coordinated experiments—such as GeoMIP referenced in reviews—have quantified that SRM can offset mean surface warming relatively quickly, while model intercomparisons also reveal substantial regional shifts in precipitation, atmospheric circulation, and extreme event patterns if SRM is applied or abruptly halted [1] [2]. CDR’s modeled outcomes demonstrate a more direct path to lowering radiative forcing, but models flag scale, cost, and ecological limits: the removal rates needed to meet stringent temperature targets exceed current technological deployment and could compete with land and ocean uses [1] [3].
3. Risks identified by recent institutional reviews: ozone, hydrology, ethics, and social disruption
Multiple recent analyses underscore non‑trivial environmental and societal risks. Stratospheric aerosol approaches could degrade ozone, alter precipitation patterns and produce acid deposition; marine interventions and large-scale ocean fertilization have documented ecological side‑effects and low efficacy in long-term carbon storage. CDR pathways such as large-scale afforestation or BECCS impose land‑use and biodiversity tradeoffs, while engineered CDR technologies face cost and energy constraints [2] [5] [3]. Authors also highlight governance, equity, and ethical dilemmas: unilateral SRM deployment by wealthy actors could impose cross-border climate consequences, and the research agenda itself risks political capture or premature normalization of technological fixes in lieu of emissions reduction [5] [6].
4. Where researchers agree—and where they diverge—on plausibility and policy timing
Scientific consensus recognizes the theoretical feasibility of both families of interventions but diverges sharply on readiness and desirability. Reviews emphasize that CDR is conceptually less risky and more aligned with long‑term climate stabilization, yet current CDR capacity is orders of magnitude below what would be required for aggressive targets, making scale-up dependent on policy, finance, and technological breakthroughs [1] [4]. In contrast, SRM technical studies show potential for rapid temperature moderation, but the uncertainty in regional impacts, termination shock, and governance has led many scientists and policy analysts to call for strict limits on deployment and robust international oversight [2] [3]. This divergence frames the policy debate: CDR is often positioned as a complement to emissions cuts, while SRM is framed as an emergency or stopgap with profound trade-offs.
5. Recent timelines and the research frontier: cautious experimentation, not operational programs
Recent publications through 2025 document an expanding but cautious research agenda: controlled field experiments, improved climate models, and governance studies are increasing, particularly for CDR pathways and limited SRM process studies; major scientific bodies have repeatedly urged research under strict oversight rather than deployment [2] [3]. The literature from 2009 to 2025 maps a trajectory from conceptual exploration [7] to more granular risk assessments and governance proposals in the 2020s [3] [2]. Across these sources, the prevailing recommendation is clear: invest in knowledge, clarify legal and ethical guardrails, and prioritize deep emissions reductions, while treating large‑scale geoengineering deployment as a last resort given the unresolved scientific and societal uncertainties [6] [2].