Climate Disasters and Intergenerational Equity: A Fiscal Rule for Sustainable Development

Climate disasters threaten intergenerational equity by exposing future generations to rising risks. We develop a model in which a government learns about disaster risk and enforces a sustainability criterion requiring expected social welfare to be non-decreasing over time. This criterion—similar to the principle underlying the UN Sustainable Development Goals—can be decentralized through state-contingent fiscal instruments: when perceived disaster risk is high, the constraint binds and government raises a consumption tax to finance investment subsidies for resilience. Such a fiscal rule leads to intergenerational-welfare smoothing and improves asset valuations despite adverse climate news due to commitments to future resilience. Compared with a government that adopts a social discount rate lower than households’, the sustainability-constraint rule responds to disaster risk and is better aligned with observed consumption-based climate-resilience taxes, such as those implemented in Greece and Spain.