Put simply, in rainy regions, the models sometimes assume that heat waves or dry air make rivers rise—even when no rain falls. In snowy regions, they often treat PET as the main trigger for snowmelt, instead of temperature. These patterns are not physically realistic.

The study also raises concerns about long-term climate projections made using state-of-the-art AI methods. As global temperatures rise, the relationships among rain, snow, temperature and evaporation will change. If models are built on flawed logic, their predictions for future water availability could be unreliable.