The Pilot Lab Exascale Earth System Modelling (PL-ExaESM) is a "Helmholtz-Inkubator Information & Data Science" project which aims to lay the foundation for new breakthroughs in earth system modelling (ESM) on future exascale computer architectures. There is increased societal demand for very high-resolution simulations of our environment as well as a better integration of the information value chain, from observations to coupled simulations and impact assessments. Recent technology trends, which lead to more heterogeneous HPC architectures and rapidly growing data volumes, require fundamentally new programming paradigms and call for a coherent strategy for creating next-generation earth system models based on close collaboration between domain scientists and computer experts.