Alternative Types of Ambiguity and their Effects on Climate Change Regulation.

This paper focuses on different types of ambiguity that affect climate change regulation. In particular, we analyze the effects of the interaction among three types of agents, namely, the decision-maker (DM), the climate change experts, and the society, on the probabilistic properties of green-house gas (GHG) emissions and the formation of environmental policy. These effects are analyzed under two types of ambiguity: "deferential ambiguity" and "preferential ambiguity". Deferential ambiguity refers to the uncertainty that the experts face concerning whose forecast (scenario) the DM will defer to. Preferential ambiguity stems from the potential inability of the DM to correctly discern the society's preferences about the desired change of GHG emissions. This paper shows that the existence of deferential and preferential ambiguities have significant effects on GHG emissions regulation.

Ambiguity aversion, modern Bayesianism and small worlds.

The central question of this paper is whether a rational agent under uncertainty can exhibit ambiguity aversion (AA). The answer to this question depends on the way the agent forms her probabilistic beliefs: classical Bayesianism (CB) vs modern Bayesianism (MB). We revisit Schmeidler's coin-based example and show that a rational MB agent operating in the context of a "small world", cannot exhibit AA. Hence we argue that the motivation of AA based on Schmeidler's coin-based and Ellsberg's classic urn-based examples, is poor, since they correspond to cases of "small worlds". We also argue that MB, not only avoids AA, but also proves to be normatively superior to CB because an MB agent (i) avoids logical inconsistencies akin to the relation between her subjective probability and objective chance, (ii) resolves the problem of "old evidence" and (iii) allows psychological detachment from actual evidence, hence avoiding the problem of "cognitive dissonance". As far as AA is concerned, we claim that it may be thought of as a (potential) property of large worlds, because in such worlds MB is likely to be infeasible.