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“IPAT” is shorthand for a formula, first proposed in the 1970s by Commoner, Ehrlich and Holdren, that has long been used in discussing environmental impacts of human action:
In the IPAT formula, the population sets the scale of the overall impact, modified by changing patterns of affluence and technology.
The IPAT-S scenario scripting language takes the IPAT formula as a starting point, although as a model-building language it offers much more. Also, models do not have to take the IPAT form to implement them in IPAT-S: see the Sample Scripts page for examples.
There has been some debate over the IPAT formula. My belief is that many of the disagreements come from a mistaken application of the IPAT formula as a model. Instead, it is best thought of as a heuristic framework for thinking about interactions between society and the environment. It is a useful reminder that the scale of environmental impacts generally grows with the scale of human activities, but that societies can mitigate – or aggravate – their impact, depending on how they use resources (the technology factor in the IPAT equation). More discussion is available in the IPAT links on the Resources page.
Despite its popularity and usefulness, critics of the IPAT equation have pointed out a real drawback, even as a heuristic framework: the meaning of the “technology” factor is not obvious. As defined by the formula, it is the ratio of environmental impact per unit of economic output. Such a factor could either increase or decrease for many reasons, including both technology and consumption choices.
Thus, the IPAT identity has been due for revision since it was introduced in the 1970s. In 2002, researchers at Rockefeller University’s Program for the Human Environment proposed a new ImPACT Identity intended to remedy the shortcomings of IPAT as a conceptual framework for analyzing sustainability issues.
The Rockefeller University paper introduces a rich set of examples of how the ImPACT identity could be applied. These examples fit very neatly into the IPAT-S syntax. Interested users can see how the ImPACT examples translate into IPAT-S.