Functionality of Ice Line Latitudinal EBM Tenacity (FILLET). Protocol Version 1.0. A CUISINES intercomparison project

TL;DR

This paper introduces the FILLET protocol, a standardized intercomparison project for energy balance models (EBMs) used in exoplanet habitability studies, aiming to evaluate model robustness and improve consistency.

Contribution

It establishes a comprehensive intercomparison framework for EBMs, facilitating assessment of different parameterizations and their impact on climate modeling of exoplanets.

Findings

Expected variation in results due to different model parameterizations

Identification of robust climate features across models

Insights into model defects and useful parameterizations

Abstract

Energy balance models (EBMs) are one- or two-dimensional climate models that can provide insight into planetary atmospheres, particularly with regard to habitability. Because EBMs are far less computationally intensive than three-dimensional general circulation models (GCMs), they can be run over large, uncertain parameter spaces and can be used to explore long-period phenomena like carbon and Milankovitch cycles. Because horizontal dimensions are incorporated in EBMs, they can explore processes that are beyond the reach of one-dimensional radiative-convective models (RCMs). EBMs are, however, dependent on parameterizations and tunings to account for physical processes that are neglected. Thus, EBMs rely on observations and results from GCMs and RCMs. Different EBMs have included a wide range of parameterizations (for albedo, radiation, and heat diffusion) and additional physics, such as carbon cycling and ice sheets. This CUISINES exoplanet model intercomparison project (exoMIP) will compare various EBMs across a set of numerical experiments. The set of experiments will include Earth-like planets at different obliquities, parameter sweeps across obliquity, and variations in instellation and CO$_2$ abundance to produce hysteresis diagrams. We expect a range of different results due to the choices made in the various codes, highlighting which results are robust across models and which are dependent on parameterizations or other modeling choices. Additionally, it will allow developers to identify model defects and determine which parameterizations are most useful or relevant to the problem of interest. Ultimately, this exoMIP will allow us to improve the consistency between EBMs and accelerate the process of discovering habitable exoplanets.