I=PAT
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Impact = Population x Affluence x Technology is a rule-of-thumb designed to describe the key relationships of environmental impact. It is, obviously, a simplification, but it importantly describes that if population increases, affluence (consumption) or technology (efficiency) must balance out this change. In this way, the relationship clearly describes that unless these factors are kept in check, the environmental impact will increase.
Example applications
The argument around I=PAT in the 1970s between Commoner, Ehrlich and Holdren revolved around recognising the effect of a growing population on the environment. In recent decades, as material consumption has increased significantly, the focus has moved to a reliance on techno-fixes to solve the rapid growth of both ‘P’ and ‘A’.
Steps
In a given system or problem, identify the variables for P, A, and T. The units for these variables will determine the units for I.
Key concepts
- an overview of the I=PAT equation and the relationships between the variables
- an example comparing two similar scenarios, such as the impact between plastic or reusable shopping bags
- advice to the student engineer on how to use the IPAT framework to select options that reduce the impact of a system
Core resources
Similar tools…
There are links in the IPAT equation to the behaviour in Jevon’s paradox.