https://hal-insu.archives-ouvertes.fr/insu-03726968Ghil, MichaelMichaelGhilLMD - Laboratoire de Météorologie Dynamique (UMR 8539) - INSU - CNRS - Institut national des sciences de l'Univers - X - École polytechnique - ENPC - École des Ponts ParisTech - SU - Sorbonne Université - CNRS - Centre National de la Recherche Scientifique - Département des Géosciences - ENS Paris - ENS-PSL - École normale supérieure - Paris - PSL - Université Paris sciences et lettresReview article: Hilbert problems for the climate sciences in the 21st century - 20 years laterHAL CCSD2020[SDU] Sciences of the Universe [physics]POTHIER, Nathalie2022-07-28 14:15:462023-03-13 11:17:182022-07-28 14:15:49enJournal articleshttps://hal-insu.archives-ouvertes.fr/insu-03726968/document10.5194/npg-27-429-2020application/pdf1The scientific problems posed by the Earth's atmosphere, oceans, cryosphere - along with the land surface and biota that interact with them - are central to major socioeconomic and political concerns in the 21st century. It is natural, therefore, that a certain impatience should prevail in attempting to solve these problems. The point of a review paper published in this journal in 2001 was that one should proceed with all diligence but not excessive haste, namely "festina lente", i.e., "to hurry in a measured way". The earlier paper traced the necessary progress through the solutions of 10 problems, starting with "What can we predict beyond 1 week, for how long, and by what methods?" and ending with "Can we achieve enlightened climate control of our planet by the end of the century?" <P />A unified framework was proposed to deal with these problems in succession, from the shortest to the longest timescale, i.e., from weeks to centuries and millennia. The framework is that of dynamical systems theory, with an emphasis on successive bifurcations and the ergodic theory of nonlinear systems, on the one hand, and on pursuing this approach across a hierarchy of climate models, from the simplest, highly idealized ones to the most detailed ones. Here, we revisit some of these problems, 20 years later,<SUP>1</SUP> and extend the framework to coupled climate-economy modeling.