In a stable climate system, there is a fundamental balance between the solar radiation energy reaching the Earth and the reflected shortwave solar radiation and emitted longwave radiation energy leaving the Earth. The transfer of radiative energy within the Earth-atmosphere-ocean system is a complex dynamic process. Remote sensing of Earth’s radiation budget (ERB) from space is the most effective way to monitor the climate system’s radiative energy balance, verify progress toward global carbon sinks and carbon neutrality, and track large-scale climate changes. Achieving these goals requires precise, continuous, quantitative remote sensing of incoming solar radiation, reflected shortwave radiation, and emitted longwave radiation from multiple locations outside Earth’s atmosphere. Human activities can significantly alter surface albedo and atmospheric composition. Changes in surface albedo directly affect the absorption of shortwave radiation, while the increase in atmospheric greenhouse gases enhances the greenhouse effect, hindering the escape of longwave radiation energy. Most of this energy remains trapped in the atmosphere and hydrosphere, disrupting Earth’s radiative energy balance. The longwave and shortwave radiation measurements help quantify Earth’s radiation energy imbalance (EEI), with an average of 0.50?1.00 W/m² from 2005 to 2025, derived from satellite-based observations and ocean heat content measurements, and are associated with unprecedented warming in the 21st century. This imbalance, driven by increased greenhouse gases trapping longwave radiation, results in over 90% of excess heat being absorbed by oceans, exacerbating sea-level rise and extreme weather events. By continuously improving the accuracy of instrument observations and calibration, and optimizing algorithms for multi-source data analysis and fusion, the future direction of Earth’s radiation budget remote sensing lies in advancing spatiotemporally continuous monitoring of the true magnitude of Earth’s radiation energy imbalance from outside the atmosphere. Furthermore, ERB data shed light on the roles of clouds and aerosols. Clouds can cool the planet by reflecting sunlight or warm it by trapping heat, with their net effect depending on type and structure. Aerosols act as cloud condensation nuclei, influencing precipitation and radiation scattering. In essence, space measurements validate models, detect trends, and inform policy on climate mitigation. As of 2025, ongoing data from CERES and emerging satellites underscore ERB’s role in addressing global warming, emphasizing the need for sustained orbital monitoring to safeguard Earth’s habitability.

The Clouds and the Earth’s Radiant Energy System (CERES) offers the longest continuous record of outgoing longwave and reflected shortwave radiation. However, achieving complete global spatial sampling of Earth’s diurnal cycle remains a challenge. This typically requires combining geostationary satellite data, which interpolates the 24-h cycle, with polar-orbiting satellite data to derive a global Earth’s radiation energy imbalance. To address these limitations, the Space Science Center at the Institute for Advanced Study, Shenzhen University, is leading a pathfinder ERB experiment that will monitor outgoing longwave and reflected shortwave radiation using the Chang’e-7 lunar orbiter. The experiment will test the feasibility of monitoring Earth’s radiation budget from the Moon. If successful, Moon-based ERB measurements could provide a stable, long-term, highly accurate platform for global climate monitoring, overcoming traditional satellite limitations and greatly improving our understanding of Earth’s radiation energy imbalance. The Moon-based ERB (MERB) experiment is an international collaboration, with Dr. Mustapha Meftah and Dr. Alain Sarkissian from UVSQ/LATMOS contributing to instrument validation, calibration, characterization, and scientific data analysis. The MERB flight model is being ground-calibrated in a traceable radiometry laboratory at Shenzhen University. A 2.2-m-diameter, 2.0-m-long vacuum chamber is being set up within a Class 1000 cleanroom. This chamber integrates a Sun simulator, a deep-space background radiation blackbody, a terrestrial longwave radiation blackbody, and an integrating sphere light source with eight distinct wavelength bands. The spectral and radiometric responses of the total and longwave channels are calibrated against these traceable radiation targets. The MERB qualification model has successfully passed all environmental and vibration tests. The flight model has been manufactured and integrated into the Chang’e-7 orbiter, which is scheduled for launch in 2026.

Earth’s radiation energy imbalance is a crucial climate variable that constrains the global rate of climate change. While polar-orbiting and geostationary satellites remain the primary platforms for monitoring Earth’s radiation energy imbalance, a MERB experiment provides a valuable complement. Leveraging a unique and stable vantage point from Earth’s natural satellite, the Moon, this experiment greatly enhances Earth’s radiation energy imbalance monitoring, not only in tracking global trends but also in determining its absolute value with greater accuracy.