Climate Uncertainty, Real Possibilities and the Precautionary Principle

Abstract

A challenge faced by defenders of the precautionary principle is to clarify when the evidence that a harmful event might occur suffices to regard this prospect as a real possibility. Plausible versions of the principle must articulate some epistemic threshold, or de minimis requirement, which specifies when precautionary measures are justified. Critics have argued that formulating such a threshold is problematic in the context of the precautionary principle. First, this is because the precautionary principle appears to be ambiguous about the distinction between risk and uncertainty: should the principle merely be invoked when evidential probabilities are absent, or also when probabilities have low epistemic credentials? Secondly, defenders of the precautionary principle face an aggregation puzzle: in judging whether or not the de minimis requirement has been met, how should first-order evidential probabilities and their second-order epistemic standing be aggregated? This article argues that the ambiguity can be resolved, and the epistemological puzzle can be solved. Focusing on decisions in the context of climate uncertainty, I advance a version of the precautionary principle that serves as a plausible decision rule, to be adopted in situations where its main alternative—cost–benefit analysis—does not deliver.

Climate Change, Uncertainty, and Policy

“…Some proponents advise to stick with the expected utility approach and try to estimate probabilities as well as possible (Broome, 2012). Critics might argue that in contexts of deep uncertainty this either invites false precision, or leads to paralysis in decision-making, as there is no expert consensus regarding the appropriate probability estimates (Hopster, 2021).…”

“…An element that many operationalizations have in common is their reliance on a decision tripod, which consists of a damage condition, an epistemic condition and a proposed remedy (Steel, 2014). Precautionary decisions may be defensible if the envisioned damage is great, its occurrence constitutes a realistic possibility, and the remedy is effective in preventing this possibility from actualizing (Hopster, 2021).…”

Future value change: Identifying realistic possibilities and risks

“…In doing so, they fail to focus on highlighting what (from a risk perspective) are the most salient possibilities among these: the outliers and extremes, the tipping points and the catastrophes that may ensue. Hence, from a normative point of view, climate modellers should have a distinct focus on highlighting possibilities of substantial harm -provided, of course, that these possibilities satisfy the epistemic standard of being realistic (Hopster, 2021a). Axiological futurists should not fall into the same trap.…”