A Simple Integrated Assessment Model (SIAM) For the last decade I have had the privilege of teaching a third year class called Climate and Society. We cover a wide range of issues as you might imagine, but one thing I try and cover is the structure of Integrated Assessment Models (IAMs) and their role in the climate debate. My motive here is not to train up a generation of modellers, although some are bitten by the bug, but rather to expose the students to probably the most important way we conceptualise and negotiate on climate change, and from there attempt to empower them through having some understanding of the IAM world view. I approach this by getting the students to build their own IAM. In the main these students don’t have any formal economics, and their climate science is relatively qualitative. So we pare down the complexity more than I’ve seen any others attempt, in order to make the material accessible and transparent to us math/modelling phobes. The result will hopefully offend the economic/IAM orthodoxy but be illuminating for those wanting to sift through some of the entrails of the IAM world. The current product is a handout that you work your way through with the aim of incrementally building an IAM from scratch in a spreadsheet, using say OpenOffice™ or Excel™. However, before diving into the construction process we walk through the science in order to set out the structure and open up some relevant discussions. One of the end games is to calculate the cost of carbon in several ways, not to offer definitive estimates of this, but to attempt to illustrate where such estimates derive from, and the blend of assumptions and choices wrapped up in these numbers. None of this is particularly polished, although it has benefitted from a number of revisions over the years. This is particularly so for the spreadsheet model offered below, which is meant to resemble what the students themselves produce having gone through the process. If you have any thoughts or feedback to improve things please feel free to email me, but let's not get too lost in the detail. SIAM PART 1: Introduction and model description SIAM PART 2: Construction and scenario development SIAM PART 3: Costing carbon SIAM SPREADSHEET MODEL Andrew Jarvis, January 2021