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World income grows fast without verifiable climate-change impacts on the economy. The growth spell can end if climate impacts turn real but this can take decades to learn. We develop a tractable stochastic climate-economy model with a hidden-state impact process to evaluate the contributions of the expanding economy and changing impact beliefs to the social cost of carbon. Taking a dataset of estimates for the social cost as a representation of beliefs, we assess how robust climate policies are to the delays of hard information. The carbon price should rise with income to the next century, even without observed impacts. The carbon price should grow faster than the economy as long as climate warming is not enough for generating impacts that are informative about the true social cost.

We consider a model of cake-eating with private information. The model captures phenomena such as trust and "security of supply" in resource-use relationships. It also predicts supply shocks as an equilibrium phenomenon: privately informed sellers have incentives to reveal resource scarcity too late, through a supply disruption, after which they exploit the consumers' inability to immediately adjust demand. Two puzzles that a standard exhaustible-resource theory cannot explain are resolved: sellers have an incentive to overstate their resources rather than emphasize scarcity, and consumers can switch to alternatives before exhausting the resource thereby leaving socially valuable resource in the ground.

I define "generous sustainability" as a combination of two conditions: neither instantaneous maximin income nor attainable maximin income should decrease over time. I provide a formal definition and study applications to an AK economy, a Ramsey economy, and a Climate Economy. Generosity is shown to impose substantially stronger conditions on current actions compared to existing sustainability concepts. As a rule of thumb, generosity requires that GHG emissions are limited to levels that do not cause irreversible system damages if some group of people systematically value these systems.

Should public assets such as infrastructure, education, and the environment earn the same return as private investments? The long-term nature of public investments provides commitment to current preferences, which justifies lower than private returns for time-inconsistent decision markers. An institutionalized (i.e., exogenous) rule demanding equalized comparable returns removes the bias and implements the standard cost-benefit requirement. We show that such a stand-alone rule has no general welfare content: it implements Pareto efficiency if and only if preferences are time-consistent. Efficiency requires rules not only for the composition of investments but also for overall savings. Without supplementary rules for savings, accepting lower returns for long-term public assets is welfare improving.