I have historical observation, historical simulation and future simulation. Using the delta method of downscaling, I have downscaled 5 general circulation models (GCMs). I basically referred this article "https://www.nature.com/articles/s41597-019-0343-8" where they have also used perfect sibling approach to evaluate downscaled GCMs. I have not been able to understand how to apply perfect sibling approach to my case. Could anyone help me how to use perfect sibling approach? I'd appreciate if anyone could help with examples and not share the articles because I have read so many articles related to perfect sibling and I have not been able to apply to my case. I am really thankful for your genuine help.