If policy needs ethics, we might expect to find holes or gaps in allegedly “pure” policy arguments. This leads us to the second strand of hostility, which aims to sidestep ethics through direct appeals to science.
One strategy involves presenting climate goals as “derived” from science. For instance, much climate policy is based around objectives such as keeping global temperature rise below 2°C, or cumulative anthropogenic emissions below a trillion tons, and so on. Consequently, many implicitly assume that climate goals are “value free,” so that the need to discuss ethics disappears from view.
Unfortunately, philosophers of science typically argue that the practice of science is not “value free” in the relevant sense.3 The 2°C threshold for “dangerous” climate change provides a useful illustration. Procedurally, it “has emerged nearly by chance, and evolved in a somewhat contradictory fashion: policymakers have treated it as a scientific result, scientists as a political issue.”4 Substantively, the target makes implicit decisions about tradeoffs that need to be justified. For example, if two degrees would sink small island states and fry Africa, then its intelligibility as capturing the goal of avoiding dangerous climate change requires defense.
More generally, attempts to justify the two degrees threshold also raise ethical questions. To illustrate, consider one early rationale. Apparently, the target’s first appearance came in a marginal comment by the economist, William Nordhaus, who thought it “reasonable to argue that the climatic effects of carbon dioxide should be kept within the normal range of long-term climatic variation.”5 This rationale is not obviously ethically defensible. For instance, suppose someone made the parallel proposal to limit the fatalities caused by a new industrial toxin to the maximum number of deaths caused by naturally occurring diseases (such as cholera). Such a benchmark would be ethically problematic for numerous reasons: it allows additions to the total number of fatalities; it assumes that we have the right to inflict deaths comparable to those occurring naturally; it does not consider our duties to reduce both natural and human-caused fatalities; etc. Nordhaus’s rationale for two degrees raises similar objections. Consequently, it does not justify the threshold as a narrowly “scientific” or “pure policy” goal.6