The Hub Talks: Observing the Earth (water and) energy cycle from space to understand climate change

Speaker: Dr. Meyssignac is a researcher at the Laboratoire d’Etudes en Géophysique et Océanographie Spatiale (LEGOS) and at the French Space National Center (CNES) in Toulouse, France. His research focuses on understanding the variations of the global Earth energy-water cycle at regional and global scales through high precision geodetic satellite observations and modelling approaches. He investigates processes leading to changes in the Earth energy budget, theEarth energy imbalance and the response of the energy-water cycle fluxes to greenhouse gases emissions. He is the author of more than 70 research articles and a lead author of the last IPCC report. He was awarded for his work the Christian Le Provost prize from the French national science academy in 2017 and theEGU/ESA Earth observation excellence award in 2021.  He is active in the World Climate Research Program (WCRP) as a leader of the Global Energy and Water Exchanges (GEWEX) Earth Energy Imbalance assessment and the Earth Energy imbalance trend case of the WCRP lighthouse activity on explaining and predicting Earth system change.

Abstract: At decadal and longer time scales, the Earth’s global energy cycle is governed by the difference between incoming solar radiation (TSI) and outgoing terrestrial radiation (OTR). The small but persistent imbalance between TSI and OSR —known as the Earth Energy Imbalance (EEI)—is the primary driver of long-term climate change. Constraining this imbalance with sufficient accuracy is critical for understanding EEI variations in time and predicting the climate system’s response to anthropogenic forcing. Satellite observations offer unprecedented global coverage and temporal continuity, making them indispensable for tracking the key components of the energy budget. However, achieving the required precision—on the order of tenths of a watt per square meter—remains a formidable challenge due to instrument calibration, orbital stability, sampling biases, and inter-sensor consistency.

This presentation reviews the main satellite-based datasets used to observe Earth’s radiative fluxes, ocean heat content, and surface temperature. It examines how this satellite data constrain both the magnitude and variability of EEI and the associated climate feedback. We highlight the limitations of current observing systems, the inconsistency among independent datasets, and the difficulties in closing the energy budget at global scale. Moreover, we discuss emerging efforts to integrate satellite altimetry (Sentinel 3 and 6), gravimetry (GRACE-FO and NGGM), and radiometry (CERES and ECO) to improve estimates of EEI, determine its drivers and constrain the global energy budget. We outline the key remaining observational gaps and scientific questions that must be addressed to understand the processes driving temporal variations in the global energy cycle in response to greenhouse gases. One significant gap concerns the lack of observations on the role of deep atmospheric convection and its interaction with tropical circulation in modulating climate feedback. This should be a priority in the coming decade, with missions such as EarthCARE, AOS, INCUS, and WIVERN expected to address this need.

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