O seminário do Departamento de Ciências Atmosféricas do IAG/USP terá como tema: "Climate prediction and numerical analysis: questions of practical importance", com apresentação do Dr. Francisco de Melo Virissimo (London School of Economics and Political Science, United Kingdom).
Modern research in climate change relies on Earth System Models (ESMs), which are highly complex and nonlinear mathematical representations of the planet Earth. Since ESMs are too complicated to be tractable analytically, we must rely on computers to extract useful information from them. Numerically solving these models is a highly complex task, with two key practical consequences.
First, being complex and nonlinear, ESMs require the use of several numerical schemes and involves different computational strategies to accommodate for the multiplicity of scales and components present. These numerical choices vary from model and is also dependent on the user needs, as well as the computational resources available to them.
Secondly, being chaotic means that the solution of any initial value problem (IVP) is sensitive to finest detail of the IVP’s computational representation, meaning that the system’s state (or climate) can only be characterised as a distribution – therefore requiring an ensemble of simulations instead of a single one. This also means that different numerical approximations could lead to differences in the resulting distributions, particularly in shape and extreme values. This is important as it can cause ambiguity in our interpretation of future climate projections. Despite that, this issue has been largely neglected in both climate and mathematical literatures.
In this talk, I will review and discuss the use of numerical schemes in ESMs and their individual components. Using a conceptual and low-dimensional representation of the climate system, I will also present some preliminary results illustrating how different numerical methods affect the resulting climate distribution. In addition to the uncertainties from initial condition, parameter and model formulation, this study suggests a fourth level of “structural” uncertainty in climate modelling – in the numerical formulation. This has implications to the design and interpretation of climate ensembles, which brings climate change research to the core of 21st century applied numerical analysis research.
This talk will be kept as self-contained as possible and will be tailored to a non-expert audience. Hence, everyone with an interest in the subject is welcome, regardless of their academic level and/or background.
Haverá transmissão pelo canal do Departamento de Ciências Atmosféricas: https://www.youtube.com/@AtmosferaIAGUSP/live