Climate change impacts can be measured as an economic cost (Smith et al., 2001:936-941).
Climate change impacts particularly susceptible to market impacts, that is impacts that are linked to market transactions and directly affect GDP. Monetary measures of non-market impacts, e.g., impacts on human health and ecosystems, are more difficult to calculate.
Other difficulties with impact estimates are listed below:
Socioeconomic trends: Future predictions of development affect estimates of future climate change impacts, and in some instances, different estimates of development trends lead to a reversal from a predicted positive, to a predicted negative, impact (and vice versa)Knowledge gaps: Calculating distributional impacts requires detailed geographical knowledge, but these are a major source of uncertainty in climate models.
Vulnerability: Compared with developed countries, there is a limited understanding of the potential market sector impacts of climate change in developing countries.
Adaptation: The future level of adaptive capacity in human and natural systems to climate change will affect how society will be impacted by climate change. Assessments may under- or overestimate adaptive capacity, leading to under- or overestimates of positive or negative impacts.