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Methane (CH4) is one of the most important trace gases in the atmosphere owing to its role as an exceedingly effective greenhouse gas and atmospheric pollutant. Better understanding of the global methane cycle and its interactions with the Earth system is therefore necessary for robust future projections of anthropogenic climate change and assessments of multi‐gas mitigation strategies. Here we present a newly developed methane emission‐driven Earth system model to simulate the global methane cycle fully interactively. We provide an evaluation of methane sources and sinks and a full‐cycle methane budget and its change over the historic period. We further evaluate the methane atmospheric abundance and lifetime against available observations. The new methane emission‐driven model simulates all the components of the methane cycle within observational uncertainty. We calculate a total present‐day (2000–2009 decadal average) methane source of 591 Tg(CH4) yr−1 with 197 Tg(CH4) yr−1 coming from wetlands. These sources are nearly balanced by the global methane sinks amounting to 580 Tg (CH4) yr−1; reaction of methane with the hydroxyl radical in the troposphere alone removes 525 Tg(CH4) yr−1. The imbalance between sources and sinks of 11 Tg(CH4) yr−1 represents the atmospheric methane growth rate and is in fairly good agreement with current best estimates of 5.8 Tg(CH4) yr−1 with a range of 4.9–6.6 Tg(CH4) yr−1. At present‐day the model shows a maximum systematic negative‐bias of approximately 200 ppb in the methane surface mole fraction. Plain Language Summary Methane is a very important greenhouse gas. The global methane cycle needs to be understood fully to accurately model the way methane affects climate change. We describe a new version of the UKESM1 Earth system model, UKESM1‐ems, that uses emissions of methane to drive the atmospheric chemistry. In case of emissions from global wetlands, such as bogs, swamps and tundra, the methane emissions are calculated by the model during runtime. Methane emissions react directly to changes in the modeled climate. UKESM1‐ems simulates the global cycle of methane from emissions via oxidation in the atmosphere to uptake at the surface more realistically. We also test the model against measurements from satellites and ground‐based stations to ensure the relevant processes in the model behave accurately. The comparison with observations shows that UKESM1‐ems performs well and represents an improvement in simulating important processes in climate and the Earth system. However, we also found that the methane concentration in the model is too low compared to observations for the period of the twentieth and early 21st century during which human activity, especially the use of fossil fuel, is dominating the methane cycle. Key Points A methane emission‐driven configuration of the UK community Earth system model UKESM1, UKESM1‐ems, has been developed In UKESM1‐ems global wetlands are interactively coupled to the atmosphere at every timestep via methane emissions The UKESM1‐ems performs well simulating the global methane cycle including feedbacks; the global budget compares well with observations

Emissions‐driven (prognostic CO2) simulations are essential for representing two‐way carbon‐climate feedback in Earth System Models. We present an emissions‐driven land–atmosphere coupled biogeochemistry (BGC) configuration (BGCLNDATM_progCO2) in version 2.1 of the Energy Exascale Earth System Model (E3SMv2.1). This is the first E3SM configuration that performs land‐atmosphere emission‐hindcasts. Here, we document its implementation, evaluate the model's performance against observations and other models, and propose a structured evaluation protocol for such emissions‐driven simulations. We conducted transient historical simulations (1850–2014) with BGCLNDATM_progCO2 and compare them to reference simulations—a land‐atmosphere coupled simulation without BGC and a standalone land simulation with BGC, both using prescribed CO2 concentrations—and to observations. BGCLNDATM_progCO2 overestimates atmospheric CO2 concentrations by 11–23 ppm yet stays within the 40‐ppm spread CMIP6 emission‐driven models and retains physical climate properties comparable to the reference runs. The CO2 biases are partly attributed to underrepresented oceanic CO2 uptake and inadequate representations of some terrestrial processes. In general, introducing prognostic CO2 did not change physical climate metrics at the global scale but had larger regional effects, particularly over land where spatially heterogeneous CO2 and prognostic leaf area index influenced surface energy balance. Finally, we propose a general evaluation protocol including spin‐up assessment, atmospheric CO2 benchmarking, physical climate evaluation, and land biogeochemical analysis to support scientific rigor and facilitate inter‐model comparisons. The new configuration lays the groundwork for future enhancements, including improved terrestrial biogeochemical processes, integrated marine biogeochemistry, and additional human–Earth system interactions. These developments advance E3SM toward fully coupled emissions‐driven simulations, enabling more accurate carbon–climate feedback projections and informing mitigation policy by providing physically consistent carbon‐budget metrics for mitigation scenarios. Plain Language Summary Understanding the impact of carbon dioxide (CO2) emissions on climate is vital for predicting future changes and crafting effective policies. Earth System Models (ESMs) are essential tools for simulating Earth's climate and assessing various influencing factors. In this study, we extended the Energy Exascale Earth System Model (E3SM)'s capabilities so that CO2 levels are calculated directly from human and natural emissions instead of being prescribed as a single global value. This extension allows for a more realistic representation of CO2 exchange between the atmosphere and land. We conducted historical simulations from 1850 to 2014 using this new development and compared results with observations and other models. Our model slightly overestimates atmospheric CO2 levels compared to measurements but is comparable to other models in capturing key climate features. To help other researchers build and test similar “emission‐driven” models, we created a step‐by‐step evaluation framework that checks CO2 behavior, climate variables, and land‐atmosphere interactions. Our work advances E3SM modeling by accurately representing how CO2 emissions affect Earth's systems. This enhancement lays the groundwork for modeling interactions between human‐Earth interactions, thereby enabling future studies that can inform mitigation and adaption. Key Points Implemented emissions‐driven land–atmosphere biogeochemistry in E3SMv2.1 (BGCLNDATM_progCO2), enabling prognostic CO2 simulations Established a structured evaluation protocol ensuring scientific rigor and facilitating inter‐model comparisons of model performance Emissions‐driven BGCLNDATM_progCO2 simulations maintain a physical climate similar to reference runs with prescribed CO2 concentrations

This study investigates the feasibility of obtaining high-temperature (2000–2200 °C) measurements using thermionic emission from a W–La2O3 cathode in a low-pressure argon glow discharge environment. Compared to a vacuum environment, the cathode emission characteristics and temperature variation patterns in a plasma environment exhibit significant differences. These differences arise primarily from the competitive interplay between the thermionic emission cooling (TEC) effect and the ion bombardment heating (IBH) effect. Among the discharge parameters (temperature, applied bias voltage, and background pressure), the applied bias voltage is the key factor influencing this competitive interplay. Consequently, the cathode surface temperature exhibits three distinct regions as a function of bias voltage: the TEC-dominated region (10–20 V), the transition region (20–40 V), where TEC and IBH are nearly in equilibrium, and the IBH-dominated region (40–60 V). The results indicate that by adjusting the discharge parameters to place thermionic emission in the transition region, the TEC and IBH effects can be mutually offset. Under these conditions, the cathode temperature can be unambiguously determined from the measured emission current using the modified Schottky equation. This approach simplifies the functional relationship between emission current and temperature (J–T), thereby enabling high-temperature measurements to be obtained.

The atmospheric carbon dioxide (CO 2 ) concentration has been increasing rapidly since the Industrial Revolution, which has led to unequivocal global warming and crucial environmental change. It is extremely important to investigate the interactions among atmospheric CO 2 , the physical climate system, and the carbon cycle of the underlying surface for a better understanding of the Earth system. Earth system models are widely used to investigate these interactions via coupled carbon-climate simulations. The Chinese Academy of Sciences Earth System Model version 2 (CAS-ESM2.0) has successfully fixed a two-way coupling of atmospheric CO 2 with the climate and carbon cycle on land and in the ocean. Using CAS-ESM2.0, we conducted a coupled carbon-climate simulation by following the CMIP6 proposal of a historical emissions-driven experiment. This paper examines the modeled CO 2 by comparison with observed CO 2 at the sites of Mauna Loa and Barrow, and the Greenhouse Gases Observing Satellite (GOSAT) CO 2 product. The results showed that CAS-ESM2.0 agrees very well with observations in reproducing the increasing trend of annual CO 2 during the period 1850–2014, and in capturing the seasonal cycle of CO 2 at the two baseline sites, as well as over northern high latitudes. These agreements illustrate a good ability of CAS-ESM2.0 in simulating carbon-climate interactions, even though uncertainties remain in the processes involved. This paper reports an important stage of the development of CAS-ESM with the coupling of carbon and climate, which will provide significant scientific support for climate research and China’s goal of carbon neutrality.