Given the scope of the climate challenge and the slow pace of mitigation, there is growing interest in the potential for adaptation measures to reduce climate impacts. However, adaptation and mitigation are complementary, not interchangeable. Adaptation occurs at different scales than mitigation, adaptive capacity varies greatly across sectors and regions, and beyond certain limits, adaptation is likely to be infeasible. Thus, the idea of “reaching the 2°C target” with 3°C of warming but “1°C of adaptation” is not realistic.

Most integrated assessment models (IAMs) of climate economics fail to acknowledge these issues. They seek to find optimal tradeoffs between mitigation and adaptation based on inadequate representations of the climate system, climate change and its impacts, and adaptation. In general, IAMs tend to under-estimate climate damages, over-estimate the amount of adaptation that will occur and therefore under-estimate the costs and potential benefits of adaptation. The results are particularly misleading when considering policy options under extreme climate change.

While it is possible – and worthwhile – to address the weaknesses in some IAMs, policy-makers should recognize that these models have inherent limitations and the results will always be shaped by the underlying assumptions. Alternative approaches, such as risk-based frameworks and co-benefits analyses, may be more useful when designing policy or formulating negotiating positions.

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