2. PASCAL’S WAGER. The costs of climate extinction outweigh the benefits of rejecting science.

Naomi Oreskes makes a compelling case for the trustworthiness of science, its social, value-laden, and fallible character, and the conditions for objectivity. She also reveals the rather effective diversion created in public debates by many climate change skeptics. In most cases, skeptics no longer question the overwhelming, credible scientific evidence on anthropogenic, risky climate change. Instead, they argue against particular economic or social implications of potential political responses to climate change. While they balk at the idea of engaging in open dialogue about their concerns as to the various possible (political) responses to climate change, they simply deny that the latter is a scientific problem. They urge the academic community to continuously clarify the science. And even when the science of climate change is accepted they deny the severity of damages caused by climate change. The recent SCC estimate of the Trump administration is one such example. Furthermore, according to their view, evidence-based research can never reduce the uncertainties to such an extent as to allow for the implementation of climate policies.

The often-intractable conflicts about climate policy are thus not necessarily rooted in a lack of trust in climate science—but rather in disagreement on the design of climate policies.3 Any reasonable answer to this crucial question is dependent on disputed ethical values, concepts of intergenerational and intragenerational justice, preferences, and interests (as Oreskes rightly points out). But the estimates of social science concerning the costs of action and inaction, the co-benefits and unintended societal side effects of climate policy must figure prominently too in such an answer. Natural science and technology alone cannot determine appropriate climate policies. Stubbornly insisting on the facts of climate science to counter skepticism just makes environmental controversies worse.4 Due to her emphasis on criteria for the trustworthiness of natural science Oreskes does not answer sufficiently the question as to the conditions—if at all5—under which the policy assessments provided by scientific experts can both be trustworthy and legitimate, particularly given the highly disputed value judgments involved. Therefore, we need to reflect about these integrated, transdisciplinary assessments of complex socioeconomic and political aspects. How can we specify, apply, and perhaps amend Oreskes's convincing criteria for trustworthiness to provide guidance also for the social sciences in these cases?

Oreskes does not highlight the indeterminateness of climate policy. Rather she presents a simplified version of Pascal's Wager6 as applied to climate policy (see table 1). Oreskes suggests that ambitious climate policy would be beneficial even if the science supporting anthropogenic climate change turned out to be wrong. A risk-neutral decision-maker would choose ambitious climate policy, if p > C / (V-E). In other words, ambitious climate policy is a no-regret option irrespective of the probability of climate change if the mitigation costs are negative due to the co-benefits of climate action. Such benefits include reduced local air pollution after phasing out coal or less dependency on fossil fuel imports. In contrast to Oreskes, the Trump administration has discounted the damages (V) to such an extent that investments in ambitious climate policy cannot be evaluated as beneficial for US society, even if the probability of dangerous climate change is very high.

The payoffs in the climate policy wager are not merely givens that result from a state of nature—they should be understood as an emergent outcome of a social learning process. Most experts would evaluate Oreskes's no-regret argument for ambitious climate policy as overly optimistic.7 It is, however, equally pessimistic for Trump to ignore the damages of climate change for humankind as a whole by discounting future climate damages to an excessive degree —particularly when their partly irreversible character is taken into account. Rational decision-makers would choose to reduce emissions both immediately and considerably. They would launch a societal learning process designed to adapt climate policies according to new insights about future damages and mitigation costs as well as other effects and risks associated with these policies. Such a social learning process would draw on evidence from ex-post policy analysis to determine which policy instruments worked and which did not. Recent analyses of the EU ETS8 are examples of such studies. The iterative nature of the learning process is conducive to making incremental, yet successful steps in climate policy on various governance levels while avoiding irreversible lock-in effects. If democratic societies want to tackle climate change as a serious risk for current and future societies they need to engage in rational discussions and learning processes about alternative, available solutions and their (often uncertain) implications. Such discussions must include an examination of the specific risks and the pros and cons of different policy

pathways as well as interdependencies with different policy fields, governance levels, and time scales. A scenario in which human-induced climate change transpires to be a mistaken hypothesis would then be only one of many different possible scenarios—though a rather extreme and unlikely one, as Oreskes herself suggests.

Salient examples of difficult climate policy issues include: the evaluation and comparison of climate damages in different regions; appropriate prices on CO2 emissions for different countries; the sector(s) that should be affected by a carbon pricing scheme; the specific distributional effects of carbon pricing on different social groups; policies that could soften the blow of the side effects of bioenergy, such as food insecurity, deforestation, and endangered biodiversity; the timing and size of subsidies for renewables; the socially acceptable location of wind-power turbines; the benefits and the risks of nuclear energy; the appropriate volume of international technology transfer; the potential and risks of negative emission technologies (carbon dioxide removal) or solar radiation management; and the employment effects of a rapid diffusion of electric cars.

Several ineffective and inefficient climate policy decisions have already been made precisely because such questions were not answered well. The complexity of these questions requires serious, integrated assessments to facilitate a learning process about the available policy pathways. This presupposes collaborative, scientific explorations of the various societally relevant ramifications of different pathways from different disciplinary perspectives and viewpoints.9 A more complex version of Pascal's Wager on climate policy is needed particularly when assuming the irreversibility of some climate damages. The burden of proof in risk societies thus mainly lies on assessments of policies to show that a particular climate policy choice is better than its viable alternatives. Such an assessment has to consider a policy's overall effects, side effects, and co-benefits that must be gauged against the backdrop of Sustainable Development Goals and other policy goals or values. Jointly with the stakeholders and decision-makers involved, scientific experts would act as cartographers of policy alternatives while decision-makers remain the navigators.10 We highly appreciate Oreskes's thoughts concerning the trustworthiness of (climate) science. Yet we stress the need for more focus on the policy assessments to facilitate a better public debate about different solutions and their implications.