Klaus Hasselmann (born 25 October 1931 in Hamburg)[1] is a leading German oceanographer and climate modeller. He is probably best known for developing the Hasselmann model[2][3] of climate variability, where a system with a long memory (the ocean) integrates stochastic forcing, thereby transforming a white-noise signal into a red-noise one, thus explaining (without special assumptions) the ubiquitous red-noise signals seen in the climate. He was awarded the 2021 Nobel Prize in Physics jointly with Syukuro Manabe and Giorgio Parisi for groundbreaking contributions to the "physical modeling of earth's climate, quantifying variability and reliably predicting global warming."[4]