During summer, a large portion of sea ice in the Arctic is typically covered with meltwater. We present a simple model for the evolution of melt ponds on permeable sea ice that both fits observations and allows us to understand the behavior of melt ponds in a way that is often not possible with more complex models. We use this model to show that pond coverage will increase under global warming. This work is important as melt ponds affect the overall reflectance of sea ice.