An energy budget framework to understand mechanisms of land–ocean warming contrast induced by increasing greenhouse gases Part I: Near-equilibrium state

Abstract Modeling studies have shown that surface air temperature (SAT) increase in response to an the atmospheric CO 2 concentration is larger over land than ocean. This so-called land–ocean warming contrast, φ , defined as land–mean SAT change divided by ocean-mean change, a striking feature of global warming. Small heat capacity unlikely sole cause because land-ocean contrast found equilibrium state doubling experiments. Several different mechanisms been proposed explain but comprehensive understanding has not yet obtained. In Part I this study, we propose framework diagnose based on energy budgets at top atmosphere and for atmosphere, which enables decomposition contributions from effective radiative forcing (ERF), climate feedback, capacity, transport anomaly . Using framework, analyzed abrupt quadrupling using 15 Coupled Model Intercomparison Project Phase 6 (CMIP6) Earth system models. near-equilibrium (years 121-150), 1.49 ± 0.11, primarily induced difference ERF capacity. We ERF, tend cancel each other, leading small inter-model spread compared large individual components. without contribution, are major contributors shows weak negative correlation with sensitivity.