The interest shown by policy makers and economists in the precautionary principle indicates the importance of model uncertainty in global warming policy. I show that through robust control, policy makers can implement the precautionary principle to regulate a stock pollutant, and I analyze its...

This paper analyzes optimal fiscal policy with ambiguity aversion and endogenous government spending. We show that, without ambiguity, optimal surplus-to-output ratios are acyclical and that there is no rationale for either reduction or further accumulation of public debt. In contrast, ambiguity...