KISS (Keep It Simple, Stupid!) is advice often given in presentation-skills training. The KISS principle is, in my view, also a good idea when presenting information about Earth’s climate because keeping it simple is vital for transparency. I hope that anyone can understand what this model does and what its assumptions are.
KISS is set up to test two hypotheses:
1. Carbon dioxide levels are rising in the atmosphere because human activities are putting it there.
2. The global mean temperature is rising because carbon dioxide levels are rising.
KISS allows you to compare predictions, based on these assumptions, to what really happened. If the model and data match reasonably well, this is evidence in favour of the hypotheses. If they don’t match, the hypotheses are flawed. The idea is that you play with the model, get your head around its very simple assumptions, and then make your own mind up about whether you believe the hypotheses.
If you do accept that the model works, KISS can then be used to make predictions about future climate change. In particular, how late can we leave it before we have to begin reversing the ever-increasing human production of CO2?
If you’re interested in the fine details of the calculations, download the html-file and look at it with a text editor. All the science is in lines 718-728 and 731-746. In fact, the key lines are 722-724 and line 737. That’s it, 4 lines of code! I told you it was simple.