Risk-Risk Analysis and SRM: Moving Beyond Misunderstanding

Risk-risk analysis (RRA), sometimes called “multi-risk analysis,” is a framework for comparing how policy options change risks – reducing some risks while potentially increasing others, or shifting them across populations.¹ All too often, decision-making is siloed, focusing narrowly on one risk or opportunity. By adopting a broad scope that explicitly considers multiple risks and trade-offs, RRA widens policy analysis beyond a narrow focus toward a more comprehensive or holistic analysis of multiple outcomes in complex systems.

Further, RRA can go beyond evaluation of one policy option or intervention to compare the multiple risks associated with alternative future scenarios in which alternative decisions are pursued. A comprehensive RRA seeks to help decision makers account for multiple policy paths and their interactions, indirect effects, distributional consequences, and dynamic system responses, even though many of these complexities can be difficult to assess fully in practice. RRA thus helps overcome siloed thinking, advancing more holistic analyses of complex systems.² The RRA framework is well established and has been used to improve policy analysis in food safety, transportation, mental health, environmental protection, and many other domains.

In the evaluation of strategies to address climate change, RRA can help policymakers and the public better understand the implications of multiple paths forward.³ Although climate policy options such as deep reduction of greenhouse gas emissions, large-scale carbon dioxide removal, widespread adaptation, and SRM might each or jointly reduce climate risks, they could also introduce new risks, both climate and non-climate related.⁴ RRA provides a systematic approach to identifying these multiple risks, comparing their importance, and developing policy options to reduce overall risk.

Many of the recent critiques of RRA as applied to SRM adopt a narrow interpretation of RRA as a static, technocratic comparison between the risks of SRM and the risks of climate change without SRM.^5,6 This leads to the mistaken view that RRA inherently privileges SRM over other climate policy options, overemphasizes quantifiable risks while discounting qualitative ones, and disregards the importance of public values and ethics. But these are misunderstandings of RRA.

Here we examine several critiques of applying RRA to SRM and clarify important differences between narrower and broader conceptions of RRA, focusing on four dimensions: the policy options to be evaluated, the risks to be considered, the means for comparing options, and the implications of including SRM in an analysis.

Critique #1: The mistaken view that applying RRA to SRM inherently ignores other climate policy options.

Some critics worry that applying risk-risk analysis to SRM implicitly narrows the policy conversation by focusing attention on SRM while sidelining other possible responses to climate change. Actually, a well-designed RRA does the opposite: it compares multiple options and their diverse impacts, rather than narrowly focusing on any single option or impact in isolation.

RRA does not frame climate policy as a binary choice between deploying SRM and enduring worsening climate change. RRA does not inherently compare SRM risk only against climate risk. Instead, RRA analyzes the multiple risks affected by multiple policy options: it encourages evaluation of a broad set of pathways, expanding the space of options rather than narrowing it. These pathways may include more ambitious mitigation of greenhouse gas emissions, large-scale carbon dioxide removal, widespread adaptation, SRM, and combinations of these strategies within a larger policy portfolio.

Each option carries its own profile of risks and potential benefits, which may interact, substitute for, or reinforce one another. Different interventions may also reshape incentives, institutions, technological development, geopolitical dynamics, and future policy choices, thereby influencing subsequent risks and responses in dynamic ways. Just as SRM may have these effects, so too may ambitious greenhouse gas mitigation or carbon dioxide removal. This is why RRA emphasizes evaluating them together, recognizing that no single intervention will be sufficient or free of trade-offs. By comparing multiple risks across multiple options, RRA helps ensure that important choices are not obscured and unfamiliar risks are not overlooked.⁷

Critique #2: The concern that RRA overemphasizes quantifiable risks and understates qualitative ones.

Some critics of RRA assert that it is impractical to compare the risks of SRM with those of climate change, especially across social, political, and environmental dimensions. But RRA can explicitly consider such diverse risks, including those that are not easily quantified. The sociopolitical risks of SRM, such as mitigation displacement, international conflict, termination shock, and governance failure, may be harder to quantify, but must still be taken seriously and compared along with biophysical risks that are more amenable to quantification.

RRA calls for all of these risks to be included in analysis, helping decision makers and the public overcome siloed neglect of important impacts, while also recognizing the challenge of analyzing some risks, and motivating improved methods for understanding and assessing them.³ A core strength of RRA is its ability to identify unintended effects and illuminate trade-offs among risks that differ widely in nature, uncertainty, and measurability. Indeed, recent work employing RRA has prominently emphasized the geopolitical risks and governance challenges of SRM.⁷

Critique #3: The misconception that RRA is technocratic and omits public values and ethics.

Some critics worry that structured risk analysis can crowd out ethical reflection. Yet, values and ethics are integral to RRA. Indeed, reducing risk is itself an ethical commitment.⁸ Identifying and mitigating harms, especially for vulnerable communities, is not a retreat from moral reasoning but an expression of it. Because policy choices inevitably involve complex and interacting risks, simple moral rules that may initially appear attractive can overlook important trade-offs. Structured comparison helps make those trade-offs visible so they can be debated openly.

The RRA framework compares not only the probability and consequence of each risk but also their timing, uncertainty, distribution across communities, valuation, and acceptability.⁹ Decisions about SRM confront important uncertainties and contested values. RRA is not a prescriptive decision rule, nor does it impose a single metric or value system. It supports diverse evaluative approaches, including cost–benefit analysis, multi-criteria analysis, precautionary reasoning, justice-oriented frameworks, and goal-based approaches.¹⁰

Some critiques propose participatory inclusion as an alternative to structured policy analysis such as RRA. But RRA and meaningful participatory inclusion are not in conflict. Rather, they are mutually supportive. RRA informs public deliberation by identifying who may be affected and how. Hence RRA is actually necessary for successful democratic participation. Without a systematic framework to identify multiple impacts comprehensively, it would be unclear which groups need to be included; an ostensibly participatory process might just privilege the most visible risks or the loudest voices (or the leanings of the process organizer) while neglecting impacts that are less prominent or that disproportionately affect marginalized groups. Indeed, overcoming the problem of “omitted voices” and “disregard” is one of the foundational goals of RRA.^7,11

Critique #4: The claim that conducting RRA on SRM is an implicit endorsement of SRM.

A fourth critique suggests that analyzing the risks of SRM implicitly legitimizes or endorses it. This interpretation conflates analysis with advocacy. Nothing in the RRA framework assumes that SRM is desirable or inevitable. Indeed, RRA studies of SRM have helped draw attention to the potential risks of SRM.³

Excluding SRM from RRA, or precluding RRA of SRM, does not eliminate the possibility that SRM might be pursued (by someone, whether collectively or unilaterally). Ignoring risks in complex systems does not make them disappear. Indeed, avoiding the careful evaluation offered by RRA may instead increase the risk of unilateral, hasty, and poorly governed SRM deployment. Structured comparison of multiple risks and options is especially important when policy choices may have global consequences and long time horizons. By making competing options, risks, uncertainties, and assumptions more explicit, RRA supports more informed, transparent, and accountable decision-making and governance.

As the world surpasses 1.5°C of anthropogenic global warming, and as interest in SRM rises, options for SRM must be evaluated with careful expertise, ethics, democratic participation, and precautionary scrutiny. Risk-risk analysis (RRA) helps highlight the multiple benefits, risks, trade-offs, and uncertainties involved, supporting more comprehensive understanding, more inclusive participation, and more transparent and sensible decision-making.

Far from favoring SRM or any one policy option, appropriately broad formulations of RRA help guard against unexamined assumptions, neglected impacts, omitted voices, policy polarization, and hasty decisions. By incorporating sociopolitical as well as biophysical risks, RRA enables more inclusive and informed governance.

Choosing not to evaluate SRM through structured multi-risk comparison will not eliminate its potential harms – it will only make them harder to anticipate and mitigate.