specific contexts, adaptation generally is cost-effective . The Global Commission on Adaptation estimated the benefits and costs of five illustrative investments and found benefit-cost ratios ranging from 2:1 to 10:1. However, it also noted that 'actual returns depend on many factors, such as economic growth and demand, policy context, institutional capacities and condition of assets' . A review of ex-ante cost-benefit analyses for 19 adaptation-focused projects in Africa financed by the Green Climate Fund  shows benefit-cost ratios in a similar range. Using a 10% discount rate, as used by many of GCF's accredited entities, the benefit-cost ratio for individual projects ranges from 0.9:1 to 7.3:1, the median benefit-cost ratio is 1.8:1 and total ratio across all 19 projects is 2.6:1. When using lower discount rates, as some entities do for climate projects, the benefit-cost ratio is even higher, reflecting the front-loaded costs and back-loaded benefits of many adaptation investments. Using a 5% discount rate, the overall benefit-cost ratio of the GCF projects is 3.5:1, with a range from 1:1 to 11.5:1 and a median ratio of 2.4:1 . In addition, many proposals have activities for which further benefits were not estimated due to the difficulty of attributing benefits directly to the intervention. The benefits of adaptation measures for infrastructure and others with clear market impacts are often easier to estimate than for policy interventions and where markets may not exist, such as ecosystem services .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report