The Royal Swedish Academy of Sciences has awarded a share of this year’s Nobel Prize in Physics to Klaus Hasselmann in acknowledgment of his contribution to ‘the physical modelling of Earth’s climate, quantifying variability and reliably predicting global warming’. Among Prof. Hasselmann’s long list of outstanding achievements, ESA also recognises him as one of the ‘fathers’ of ESA’s first Earth observation mission, ERS-1, which has been key to understanding our changing planet and which paved the way to modern techniques in observing Earth from space.