How harmful are restrictions on adapting to climate change?

▶ Adaptation restrictions will affect the level and composition of climate change. ▶ Assuming optimal adaptation will lead to suboptimal mitigation policies. ▶ Mitigation can compensate for some adaptation restrictions but not all. ▶ Mitigation strategies should be flexible to respond to adaptation restrictions. The dominant assumption in economic models of climate policy remains that adaptation will be implemented in an optimal manner. There are, however, several reasons why optimal levels of adaptation may not be attainable. This paper investigates the effects of suboptimal levels of adaptation caused by different types of adaptation restrictions, on the composition and level of climate change costs and on welfare. We find that especially restrictions to the effectiveness of adaptation at more extreme levels of climate change can be very harmful. Furthermore we show that the potential of mitigation to offset suboptimal adaptation varies from being essential in case adaptation becomes ineffective at higher temperature increases, to being largely ineffective in case of short-term inaction. However, in all cases the short-term recommendation is to increase mitigation levels slightly above what is normally recommended, and to keep mitigation policies flexible enough to be able to respond when adaptation restrictions become more prominent. It is clear that by reducing adaptation restrictions, in combination with adjusting the optimal level of mitigation may keep the costs of adaptation restrictions limited, and thus generally it is very harmful to ignore existing restrictions on adaptation when devising (efficient) climate policies.