The scientists created a simple model to predict how glaciers in the European Alps gain or lose ice each year. They used only monthly rainfall and temperatures as inputs. The model was tested on 15 glaciers with known data and performed well. It was then used on other glaciers without data and still worked effectively. By applying the model to all glaciers in the Alps, they were able to show how changes in temperature and rainfall have affected glacier ice over the past 200 years.