Buggy benefits of more fundamental climate models

A defining attribute of global-storm resolving models is that modelling is replaced by simulation.  In addition to overloading the word “model”  this avails the developer of a much larger variety of tests, and brings about a richer interplay with their intuition.  This has proven helpful in identifying and correcting many mistakes in global-storm resolving models that traditional climate models find difficult to identify, and usually compensate by “tuning.”  It also means that storm-resolving models are built and tested in a fundamentally different way than are traditional climate models. In this talk I will review the development of ICON as a global storm resolving model to illustrate how this feature, of trying to simulate rather than model the climate system, has helped identify a large number of long-standing bugs in code bases inherited from traditional models; how this can support open development; and how sometimes these advantages also prove to be buggy.