AI summaryⓘ
The authors discuss how Earth System Models (ESMs), which simulate the global climate, require more computing power as they get more detailed and complex. They point out that while computers are getting more powerful, they are not becoming proportionally more energy efficient, which leads to higher energy use and carbon emissions. The paper looks at how the climate research community has started to measure the energy and carbon costs of their model simulations more carefully, moving from informal estimates in one project phase (CMIP6) to formal standards in the next (CMIP7). Using real simulations, the authors show how different ways of measuring energy use and carbon emissions affect the reported impact. They also suggest how to standardize these measurements for future climate modeling collaborations.
Earth System ModelsHigh-Performance ComputingModel Intercomparison ProjectsCarbon AccountingEnergy EfficiencyCMIP6CMIP7Climate SimulationComputational CostEnvironmental Impact
Authors
Sergi Palomas, Pablo Aparici, Gladys Utrera, Mario Acosta
Abstract
Earth System Models (ESMs) rely heavily on High-Performance Computing (HPC) resources to simulate global climate. As these models evolve, their computational demands continue to grow, driven by three factors: (1) finer spatial grid resolutions, (2) the integration of complex biogeochemical processes (e.g., atmospheric chemistry, interactive vegetation, land use, and ice sheets), and (3) larger climate ensembles to manage uncertainty. Historically, growth in peak computing performance (FLOP/s) has outpaced improvements in energy efficiency (FLOP/Watt), increasing total HPC power consumption. Despite the central role of Model Intercomparison Projects (MIPs) in climate research, quantifying their computational and environmental costs has received limited systematic attention. This paper examines the evolution of climate model carbon accounting from voluntary post-hoc estimation in the Coupled Model Intercomparison Project phase 6 (CMIP6) to standardized accounting under the newly established CMIP7 Task Team on Energy Consumption. Using high-resolution Destination Earth simulations on MareNostrum 5, we empirically evaluate how different accounting boundaries (operational, active-only, and embodied carbon) impact reported energy, carbon emissions, and financial costs. Finally, we outline key methodological considerations for standardizing energy and carbon accounting for Model Intercomparison Projects (MIPs).