## 2 Importance of ERB at TOA and EEI Measurements for the Next Decades
Other influences include regional changes such as a reduction in Saharan dust affecting North Atlantic warming, the radiative effects of wildfires (e.g., a \(-0.18\) Wm\({}^{-2}\) effective radiative forcing between 2014 and 2022 [32]), and potential modulation of local energy fluxes due to ocean circulation changes (e.g., Atlantic Meridional Overturning Circulation, AMOC) and the so-called Cold Ocean-Warm Land (COWL) effect [33]. Overall, the observed acceleration in EEI reflects a complex interplay of anthropogenic forcing, feedback mechanisms, and natural variability. Understanding how reductions in aerosols contribute to warming via cloud changes remains a key challenge. The temperature peak of 2023 likely results from a combination of factors--GHGs, aerosols, volcanic activity, solar variability, El Nino-Southern Oscillation (ENSO) dynamics, and transient ocean-land interactions. Whether the net EEI is directly linked to this temperature peak remains an open question that requires further investigation. Monitoring EEI is therefore essential for quantifying the rate of global warming and tracking heat accumulation in the climate system [3]. It is a key metric for validating climate models and improving projections of future scenarios. Moreover, EEI helps disentangle the contributions of different forcing agents, such as GHGs, aerosols, and natural variability, and serves to guide mitigation and adaptation policies by directly measuring changes in Earth's energy state [34]. EEI leads to heat accumulation in the atmosphere, oceans, and land, thereby accelerating cryospheric melt [5]. As a result, this energy surplus drives global temperature increases, sea-level rise, and the growing intensity and frequency of extreme weather events (IPCC, 2021). Despite the fundamental role of EEI in governing the climate system, the ERB observational capacity is rapidly declining as essential satellite missions are decommissioned [35]. To avoid potential gaps and setbacks, since the 2010s, we have actively pursued alternative observation strategies based on the use of small satellites (Uvsq-Sat constellation) to complement measurements made by CERES. We now look forward to the timely implementation of the Libera mission (named after the Roman goddess [PERSON], who is sometimes associated with fertility and, on rare occasions, identified with [PERSON]), which is scheduled for launch in late 2027 aboard NOAA's Joint Polar Satellite System-3. This mission will be able to conduct observations in parallel with the Uvsq-Sat NG demonstrator, which was launched into orbit in March 2025. The data provided by these satellites over short time periods are also highly valuable. In addition to these efforts, the Earth Radiation Measurement (ERM) instruments flow aboard the Fengyun-3 (FY-3) series of Chinese satellites since 2008 [36; 37] have provided continuous broadband and spectral measurements, contributing to long-term monitoring of the Earth's radiation budget. Furthermore, the Moon-based Earth Radiation Budget (MERB) instrument aboard Chang'e-7 [38] will enable complementary observations of Earth's radiation budget from the Moon starting in 2026-2027. These insights underscore the critical importance of maintaining and enhancing high-precision satellite observations to disentangle the intricate drivers of Earth's radiative energy balance and improve projections of future climate change. Indeed, continuing existing missions and proposing new ones reduce the likelihood of data gaps. This continuity is also essential for supporting the validation of datasets such as ERA5, the fifth-generation global reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). While ERA5 does not assimilate ERB measurements, these observations are widely used by the ECMWF and other major climate modeling and reanalysis centers to independently evaluate and improve the accuracy of atmospheric, land, and oceanic variables estimated at high temporal and spatial resolution.