Uncertainty and unintended consequences run rampant throughout climate change. Our changing climate itself is largely a product of unanticipated and unintended consequences of industrialization. Scientists are uncertain about the relative contributions of different causes of climate change and the likely magnitude, speed, and location of the many likely effects. New technologies shift the landscape of future scenarios and of feasible policy alternatives, but much remains unknown about their likely effectiveness and possible unintended impacts. Economists are unsure about the economic consequences of climate change or of proposed policy solutions. Human behavior is unpredictable. Distributive impacts are unclear, both within and between countries. The range of possible impacts complicates adaptation planning.

Uncertainties affect the ways people see problems and evaluate alternatives. Professionals face different problems in the face of uncertainty. Scientists must decide how to communicate uncertainties in their work and how to reduce uncertainties through additional research. Philosophers disagree about the right thing to do in a given context. Policy makers from the local to the international levels to must assess the need for action and the merits of different policy options, and how much uncertainty can be tolerated for any given option. Judges and lawyers are faced with decisions about assigning and allocating responsibility when causal links are extremely complex and causes are spatially and temporally distant from effects. Corporate and environmental advocates see different challenges and opportunities in the uncertainties. All interests use and manipulate uncertainties to support their interests, often relying upon uncertainty to cloak the values and interests that lie at the heart of debates over climate policy..

Uncertainty can result from lack of information or from disagreement about what is known or even knowable. Some uncertainties may be reducible through further research but others are inherent in the complexities of the climate change problem. The types of uncertainties are related to the level and types of risks that may be tolerated under various policy options.

This paper will begin with an overview of sources of uncertainty in climate science and science policy and some of the ways that scientists, philosophers, judges, and policy makers deal with uncertainty. Scientists and others have developed conventions for portraying uncertainty in results and portraying them to lay audiences. Philosophy provides theories about rights and duties and how responsibility for consequences may depend on contextual factors such as degrees of understanding. Law has devised procedures to manage uncertainty including burdens of proof and rules of evidence. Different decision rules such as the precautionary principle have been applied to policy decisions involving uncertainty. Insights from these fields will be used to analyze the ethical dimensions of attributing responsibility under conditions involving uncertainty, such as those presented within the context of climate change, and how policy makers might improve the ways they deal with uncertainties. Issues to be addressed include how uncertainty affects the allocation of responsibility, how uncertainties of different types of risks should be balanced, how the geographical and economic distribution of risks should be considered, how uncertainties can lead to bad decisions and unintended consequences, and the importance of portraying and managing uncertainties in climate science and climate policy. Recommendations will be made as to how scientists and policy makers might portray and manage uncertainties in order to illuminate the policy process and allow decision makers to focus attention on different values and interests at the core of climate policy debates. Adding a clearer consideration of values and interests to the science of climate change will allow decision makers to reach better informed, fairer, and more resilient decisions regarding both the mitigation of and adaptation to climate change.