When climate impact costs do not add up: do local policy assessments align with global macroeconomic insights? A case study of France

Climate change is expected to cause increasingly severe economic and social disruptions, making adaptation a key pillar of climate policy. Assessing the economic costs of climate impacts is essential to inform adaptation strategies, especially when these costs are used to calibrate the scale of adaptation investments and to weigh adaptation needs against other policy priorities. Yet, estimates of these costs vary widely across studies. Here we compare the estimated economic cost of climate change for France across two lines of evidence: international macroeconomic studies and national policy documents. We find that recent macroeconomic literature, especially econometric studies, produces much higher cost estimates than those that can be inferred from aggregating national policy assessments. This discrepancy can be attributed to methodological lag, limited sectoral coverage, lack of monetization, and the omission of cross-border effects. Besides, we also show that while the national institutional literature is extensive, many broad impact categories lack comprehensive quantification, and even fewer are monetized.