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What risks do experts highlight in geoengineering proposals?
Executive Summary
Experts converge on a concise set of core risks posed by geoengineering proposals: uncertain physical side‑effects, governance and geopolitical hazards, and moral‑hazard or policy diversion from emissions cuts. Leading reviews and position statements warn that interventions like solar‑radiation management (SRM) and large‑scale carbon‑dioxide removal (CDR) could cool temperatures while leaving critical problems—such as ocean acidification and ecosystem damage—unaddressed, and could precipitate abrupt, damaging outcomes if halted or mismanaged [1] [2] [3] [4].
1. Why scientists fear 'termination shock' and abrupt shocks to society
Experts repeatedly flag the risk of an abrupt halt to SRM as among the most dangerous single outcomes: a rapid rebound warming called termination shock that could outpace adaptation capacities and trigger cascading ecological and social crises. Multiple analyses describe this mechanism as a global catastrophic risk because SRM suppresses warming by offsetting radiative forcing without removing CO₂; stopping injections would expose ecosystems and infrastructure to rapid warming at rates far faster than historical baselines, producing high climate‑velocity events and extinction risks [2] [5] [4]. The literature emphasizes that termination shock is not merely hypothetical but flows directly from how SRM functions, making long‑term governance, durable commitments, and fail‑safe planning central to any credible assessment [2] [6].
2. Regional winners and losers: unequal climate side‑effects and equity questions
Geoengineering models show uneven regional impacts on temperature and precipitation that create distributional winners and losers, stoking ethical and geopolitical disputes about who controls interventions and who bears harms. Studies and policy statements highlight risks such as altered monsoons, African drought risk, intensified North Atlantic hurricane activity, and Amazon dieback under uneven or unilateral deployment, stressing that regional climate trade‑offs could aggravate food security and displacement in vulnerable regions [1] [4] [7]. Scientific uncertainties about spatial patterns of change make it difficult to predeclare "safe" parameter ranges; consequently, experts call for inclusive governance and explicit attention to environmental justice and Indigenous rights to avoid reproducing or amplifying historical inequalities [3] [7].
3. Physical side‑effects: ozone, ecosystems, and marine chemistry left behind
Beyond temperature metrics, experts identify distinct biophysical side‑effects that SRM cannot prevent and in some cases may exacerbate. Probable hazards include stratospheric ozone depletion at high latitudes, modified diffuse versus direct radiation altering plant productivity, and continued ocean acidification because SRM does not remove atmospheric CO₂; these changes carry implications for human health, agricultural yields, and marine ecosystems that remain poorly quantified [5] [4]. Peer reviews call out the insufficient ecological coupling in many climate models: while temperature responses are modeled, downstream impacts on biodiversity, ecosystem services, and atmospheric chemistry are largely uncharted, creating large error bars on any risk–benefit calculation [4] [8].
4. Governance gaps, geopolitics, and the specter of 'rogue' deployment
Analysts underscore that current governance frameworks are inadequate to manage experiments or deployment given SRM’s transboundary effects and CDR’s land‑use implications, creating high risks of international friction. The Carnegie review and other analyses outline three governance‑amplified hazards: unilateral or "rogue" deployment by states or private actors, a weakening of multilateral cooperation as actors rely on technological fixes rather than emissions diplomacy, and legal ambiguity over liability for cross‑border harms [2] [6]. These governance deficits interact with technical uncertainty to produce systemic destabilization risks: poorly coordinated interventions could cascade into economic, security, and ecological failures far beyond the climate system itself [2] [3].
5. The moral‑hazard problem and the imperative of comparative risk assessment
A central non‑technical concern is moral hazard: the political or psychological tendency for SRM research or the mere prospect of deployment to reduce urgency on mitigation and emissions reductions. Multiple sources warn that relying on geoengineering as an "insurance policy" can institutionalize delay, creating an overshoot risk where society becomes dependent on interventions whose side‑effects accumulate and whose termination would be catastrophic [9] [2]. Experts therefore insist on robust, transparent, quantitative comparisons of risks and benefits—covering mortality, air‑pollution trade‑offs, ecological damage, and governance costs—before allowing field experiments to scale [8] [3].