These models cannot, nor do they claim to, represent the real world. It is very important for potential users of IAMs to understand the limitations of these models before using the model results. The complexity of natural and social systems cannot be captured by IAMs. The full consequences of policies considered will not be known for decades or centuries. Over this span of time, many surprises will occur.
Scientific knowledge is incomplete or absent in many areas.
Values of human, animal, and plant life, health, and diversity are difficult to quantify. Acknowledging that IAMs are limited in scope does not dismiss their usefulness. IAMs are intended to be tools for furthering our understanding of the climate change problem and not predictive models of what might take place. As such, they can provide insights into the climate change problem that are not available through other analytical and decision-making tools. The MVA Usage Guide contains a detailed discussion on the limitations of climate change IAMs.