Rising greenhouse gas concentrations and declining global aerosol emissions are causing energy to accumulate in Earth’s climate system at an increasing rate. Incomplete understanding of increases in Earth’s energy imbalance and ocean warming reduces the capability to accurately prepare for near term climate change and associated impacts. Here, satellite-based observations of Earth’s energy budget and ocean surface temperature are combined with the ERA5 atmospheric reanalysis over 1985–2024 to improve physical understanding of changes in Earth’s net energy imbalance and resulting ocean surface warming. A doubling of Earth’s energy imbalance from 0.6±0.2 Wm−2 in 2001–2014 to 1.2±0.2 Wm−2 in 2015–2023 is primarily explained by increases in absorbed sunlight related to cloud-radiative effects over the oceans. Observed increases in absorbed sunlight are not fully captured by ERA5 and determined by widespread decreases in reflected sunlight by cloud over the global ocean. Strongly contributing to reduced reflection of sunlight are the Californian and Namibian stratocumulus cloud regimes, but also recent Antarctic sea ice decline in the Weddell Sea and Ross Sea. An observed increase in near-global ocean annual warming by 0.1 ∘Cyr−1 for each 1 Wm−2 increase in Earth’s energy imbalance is identified over an interannual time-scale (2000–2023). This is understood in terms of a simple ocean mixed layer energy budget only when assuming no concurrent response in heat flux below the mixed layer. Based on this simple energy balance approach and observational evidence, the large observed near-global ocean surface warming of 0.27  ∘C from 2022 to 2023 is found to be physically consistent with the large energy imbalance of 1.85±0.2 Wm−2 from August 2022 to July 2023 but only if (1) a reduced depth of the mixed layer is experiencing the heating or (2) there is a reversal in the direction of heat flux beneath the mixed layer associated with the transition from La Niña to El Niño conditions. This new interpretation of the drivers of Earth’s energy budget changes and their links to ocean warming can improve confidence in near term warming and climate projections.

Distributed under a Creative Commons Attribution License 4.0 (CC BY). This is an open-access article distributed under the terms of the Creative Commons Attribution license , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Earth’s energy budget is sensitive to the spatial distribution of sea surface temperature and sea ice concentration (SIC) change, but the global radiative effect of changes in SIC spatial distribution has not been quantified. We show that SIC-induced radiation anomalies at the top of the atmosphere are sensitive to the location of SIC reduction in each season, which qualitatively explains how and why the effect of sea ice loss on Earth’s energy budget is determined by its spatial pattern. Idealized experiments indicate that SIC-induced surface warming is greater in the Arctic regions, resulting in a more negative Planck feedback. Global low-level cloud cover responses to Arctic and Antarctic SIC reduction are also distinct, leading to more negative SIC-cloud feedback in Arctic regions. SIC-induced albedo feedback is sensitive to latitude due to inhomogeneous solar radiation at the surface. As a result, the simulated radiative effect of SIC anomalies during 1980–2019 is dominated by variations in the spatial pattern of SIC. Effect of sea ice loss on Earth’s energy budget at the top of atmosphere depends on its spatial pattern. status released display-pdf yes is-olf no is-manuscript no is-preprint no is-journal-matter no is-scanned no is-retracted no Received 2024 Jul 1; Accepted 2025 Jan 28; Collection date 2025 Feb 28. INTRODUCTION Global warming is a result of imbalance in the Earth’s energy budget ( 1 ). In response to changes in greenhouse gases and aerosol concentration, the net radiative flux at the top of atmosphere (TOA) changes due to instantaneous radiative forcing and rapid adjustments, leading to an effective radiative forcing to the Earth’s climate system ( 1 , 2 ). Sea surface temperature (SST) and sea ice change gradually in response to radiative forcings, and corresponding changes in cloud properties, lapse rate, surface albedo, and humidity further change the Earth’s energy budget and provide feedbacks to the climate system ( 1 ). The magnitude of climate feedbacks depends on the spatial pattern and magnitude of the effective radiative forcing, leading to differences in forcing efficacies ( 3 – 5 ). Moreover, climate fluctuations alter the Earth’s energy budget by changing the spatial pattern of SST and sea ice. λ is a function of Δ T due to the state dependence of climate feedbacks ( 13 – 15 ), which can be approximated as a constant number when Δ T is not large (e.g., less than 1°). Land surface temperature responds rapidly to changes in radiative forcings and SST/sea ice, so it is not explicitly expressed in Eq. 1 . The importance of the SST pattern effect in the evolution of Earth’s energy budget has been demonstrated in previous studies, and the main mechanisms of how the SST pattern affects the Earth’s energy budget have been revealed ( 9 , 11 , 12 , 16 ). To quantify the radiative effect of SIC in the abrupt4xCO2 experiment, we design a set of abrupt4xCO2-SIC experiments with three individual atmosphere-only simulations driven by SIC of abrupt4xCO2 experiments and repeating climatological monthly mean SSTs from piControl experiments (table S1 and fig. S1). The total SIC-induced radiation change under CO 2 -induced warming is positive in our simulations ( Fig. 1, D to F ), which is consistent with the expectation that the radiative effect of CO 2 -induced SIC reduction warms the Earth system. 4 ), the SIC trend over these regions is small, so the contribution of the central Arctic Ocean to the trend of TOA fluxes is negligible; instead, the negative trend during this period is primarily induced by the SIC increase in the Antarctic regions. DISCUSSION Our findings show that the global climate effect of sea ice loss depends on its spatial pattern, and the SIC pattern effect is characterized by hemispheric asymmetry. SIC reduction in Arctic regions induces greater surface warming and a correspondingly greater radiative cooling effect due to the Planck feedback than the Antarctic regions. Cloud radiative effect changes are typically more positive when SIC reductions occur over lower latitude regions with smaller mean-state SIC and weaker lower tropospheric stability. SIC-induced albedo feedback is sensitive to latitude due to inhomogeneous solar radiation at the surface. As a result, numerical simulations indicate that the bulk radiative effect of SIC reduction with certain spatial patterns (e.g., trends during 1980–2008) could even cool Earth due to the hemispheric asymmetry of SIC change. Changes in sea ice thickness can affect the Earth’s energy budget by altering the surface albedo, and it is likely that the climate effects of sea ice

It is accepted that the climate on earth is changing due to a radiative energy imbalance at the top of the atmosphere, up to now this radiation imbalance has not been measured directly. The measurement is challenging both in terms of space-time sampling of the radiative energy that is leaving the earth and in terms of accuracy. The incoming solar radiation and the outgoing terrestrial radiation are of nearly equal magnitude – of the order of 340 W/m 2 – resulting in a much smaller difference or imbalance of the order of 1 W/m 2 . The only way to measure the imbalance with sufficient accuracy is to measure both the incoming solar and the outgoing terrestrial radiation with the same instrument. Based on our 30 year experience of measuring the Total Solar Irradiance with the Differential Absolute RADiometer (DIARAD) type of instrument and on our 10 year experience of measuring the Earth Radiation Budget with the Geostationary Earth Radiation Budget (GERB) instrument on Meteosat Second Generation, we propose an innovative constellation of Sun-earth IMBAlance (SIMBA) radiometer cubesats with the ultimate goal to measure the Sun-earth radiation imbalance. A first Simba In Orbit Demonstration satellite is scheduled for flight with QB50 in 2015. It is currently being developed as ESA's first cubesat through an ESA GSTP project. In this paper we will give an overview of the Simba science objectives and of the current satellite and payload development status. The Sun-earth Imbalance radiometer for a direct measurement of the net heating of the earth - INSU - Institut national des sciences de l'Univers Accueil Consulter Par date de rédaction, publication Consultation par type de publication Par unités de recherche Par domaine arXiv Guide utilisateur Documentation HAL Fiche Pratique × × × Loading... × Poster De Conférence Année : 2015 The Sun-earth Imbalance radiometer for a direct measurement of the net heating of the earth Steven Dewitte (1) , Özgür Karatekin (2) , Andre Chevalier (1) , Nicolas Clerbaux (1) , Mustapha Meftah (3) , Abdanour Irbah (3) , Tjorven Delabie (4) Afficher plus de détails 1 IRM - Institut Royal Météorologique de Belgique [Bruxelles] - Royal Meteorological Institute of Belgium (Avenue Circulaire 3, B-1180 Bruxelles - Belgique) 64715 "> IRM - Institut Royal Météorologique de Belgique [Bruxelles] - Royal Meteorological Institute of Belgium 2 ROB - Royal Observatory of Belgium = Observatoire Royal de Belgique (Ringlaan 3 1180 Brussels - Belgique) 90018 "> ROB - Royal Observatory of Belgium = Observatoire Royal de Belgique 3 STRATO - LATMOS (France) 391690 LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales (11 boulevard d'Alembert Quartier des Garennes 78280 - Guyancourt - France) 88261 UVSQ - Université de Versailles Saint-Quentin-en-Yvelines : UMR8190 (55 avenue de Paris - 78035 Versailles cedex - France) 81173 UPMC - Université Pierre et Marie Curie - Paris 6 : UMR8190 (4 place Jussieu - 75005 Paris - France) 93591 INSU - CNRS - Institut national des sciences de l'Univers : UMR8190 (INSU-CNRS 3 rue Michel-Ange, 75794 Paris Cedex 16 - France) 300045 CNRS - Centre National de la Recherche Scientifique : UMR8190 (France) 441569 "> STRATO - LATMOS 4 Production Engineering, Machine Design and Automation (Belgique) 418843 KU Leuven - Catholic University of Leuven = Katholieke Universiteit Leuven (Oude Markt 13 - bus 5005, 3000 Leuven - Belgique) 300656 "> Production Engineering, Machine Design and Automation Steven Dewitte Fonction : Auteur IRM - Institut Royal Météorologique de Belgique [Bruxelles] - Royal Meteorological Institute of Belgium Özgür Karatekin Fonction : Auteur ROB - Royal Observatory of Belgium = Observatoire Royal de Belgique Andre Chevalier Fonction : Auteur IRM - Institut Royal Météorologique de Belgique [Bruxelles] - Royal Meteorological Institute of Belgium Nicolas Clerbaux Fonction : Auteur IRM - Institut Royal Météorologique de Belgique [Bruxelles] - Royal Meteorological Institute of Belgium Mustapha Meftah Fonction : Auteur STRATO - LATMOS Abdanour Irbah Fonction : Auteur PersonId : 176046 IdHAL : abdanour-irbah ORCID : 0000-0003-3265-3148 IdRef : 031207707 STRATO - LATMOS Tjorven Delabie Fonction : Auteur Production Engineering, Machine Design and Automation Réduire la vue détaillée Résumé en It is accepted that the climate on earth is changing due to a radiative energy imbalance at the top of the atmosphere, up to now this radiation imbalance has not been measured directly. The measurement is challenging both in terms of space-time sampling of the radiative energy that is leaving the earth and in terms of accuracy. The incoming solar radiation and the outgoing terrestrial radiation are of nearly equal magnitude – of the order of 340 W/m 2 – resulting in a much smaller difference or imbalance of the order of 1 W/m 2 . The only way to measure the imbalance with sufficient accuracy is to measure both the incoming solar and the outgoing terrestrial radiation with the same instrument. Based on our 30 year experience of measuring the Total Solar Irradiance with the Differential Absolute RADiometer (DIARAD) type of instrument and on our 10 year experience of measuring the Earth Radiation Budget with the Geostationary Earth Radiation Budget (GERB) instrument on Meteosat Second Generation, we propose an innovative constellation of Sun-earth IMBAlance (SIMBA) radiometer cubesats with the ultimate goal to measure the Sun-earth radiation imbalance. A first Simba In Orbit Demonstration satellite is scheduled for flight with QB50 in 2015. It is currently being developed as ESA's first cubesat through an ESA GSTP project. The Sun-earth Imbalance radiometer for a direct measurement of the net heating of the earth. EGU General Assembly 2015 , Apr 2015, Vienna, Austria. pp.EGU2015-15259, 2015. ⟨insu-01145599⟩ Exporter BibTeX XML-TEI Dublin Core DC Terms EndNote DataCite Collections INSU UPMC CNRS LATMOS UVSQ