From Complexity to Simplicity and Back

Abstract

The Nobel Prize of 2021 highlighted the importance of understanding the complex dynamical processes that govern the evolution of Earth’s climate. Two of the Nobel laureates, Syukuro Manabe and Klaus Hasselmann pioneered the creation of a robust theoretical and mathematical framework for using a hierarchy of models of varying complexity to study a variety of questions, the most important of which may be: how do we quantify the effects of human activities on the Earth’s climate? Three main contributions of Manabe and Hasselmann on which this article focuses are: (i) simple radiative-convective models that study, among other factors, the effect of changes of CO2 concentration; (ii) a methodology to derive simpler, stochastic climate models from more complex, coupled models for the weather; and (iii) mathematical techniques called fingerprinting that quantify the human impact on the climate.