[adgjlsfhk1]

there is a fairly major assumption being made here which is that none of the $20M cost is coming from Fortran. Part of the reason for porting the models is ease of development and if you make development easier, that $20m can go down pretty quickly.

[milancurcic]

As a real-world counter-example, CLiMA (Julia) lists 54 people on their Sci&Eng team, and the project has been going for several years now. It is far from production ready. Granted, they tackle everything at once (atmosphere, ocean, data assimilation, machine learning etc.). I'm a big fan of the project and wish it the best. This is to illustrate what a huge endeavor it is to build a system like this, regardless of the implementation language.

[milancurcic]

Developing projects like this in Fortran is not any more difficult than other languages. I can't speak to Julia because I don't understand it well enough, but in my experience writing this kind of code in Fortran is more natural and easier than in Python + numeric/array/accelerator libraries. The key unfulfilled need is to have Fortran compilers do offloading efficiently for you. Then, there's no comparison.