Having been down a similar route with my own simple model which replicates HADsstV3 to a Pearson R^2 of 0.9 for monthly data, I’m happy to put up this model which achieves an accuracy of R^2=0.95 for smoothed data, using a slightly different technique. Sunspot numbers are a major component in this model by Andrew McRae, although so far as I can tell there is no integration to simulate ocean heat retention as there is with my own effort. Hopefully, he’ll make the spreadsheet available for sharing to interested parties:
I was inspired by the work of Dan Pangburn and decided to try to create a simple climate model using the external solar magnetic forcing and internal 60yr ocean cycle as the main factors, with a bit of CO2 thrown in just so it doesn’t feel left out.
The results were quite… interesting.
Here is a screen shot of the model output compared to measurements, plus a few background details in the caption of which I’m sure all of you are already aware but I wanted to write the caption for a potentially wider audience.