Heat stored in the Earth system: where does the energy go?

Author(s)

Karina von Schuckmann, Lijing Cheng, Matthew D. Palmer, James Hansen, Caterina Tassone, Valentin Aich, Susheel Adusumilli, Hugo Beltrami, Tim Boyer, Francisco José Cuesta-Valero, Damien Desbruyères, Catia Domingues, Almudena García-García, Pierre Gentine, John Gilson, Maximilian Gorfer, Leopold Haimberger, Masayoshi Ishii, Gregory C. Johnson, Rachel Killick, Brian A. King, Gottfried Kirchengast, Nicolas Kolodziejczyk, John Lyman, Ben Marzeion, Michael Mayer, Maeva Monier, Didier Paolo Monselesan, Sarah Purkey, Dean Roemmich, Axel Schweiger, Sonia I. Seneviratne, Andrew Shepherd, Donald A. Slater, Andrea K. Steiner, Fiammetta Straneo, Mary-Louise Timmermans, Susan E. Wijffels

Abstract

Human-induced atmospheric composition changes cause a radiative imbalance at the top of the atmosphere which is driving global warming. This Earth energy imbalance (EEI) is the most critical number defining the prospects for continued global warming and climate change. Understanding the heat gain of the Earth system – and particularly how much and where the heat is distributed – is fundamental to understanding how this affects warming ocean, atmosphere and land; rising surface temperature; sea level; and loss of grounded and floating ice, which are fundamental concerns for society. This study is a Global Climate Observing System (GCOS) concerted international effort to update the Earth heat inventory and presents an updated assessment of ocean warming estimates as well as new and updated estimates of heat gain in the atmosphere, cryosphere and land over the period 1960–2018. The study obtains a consistent long-term Earth system heat gain over the period 1971–2018, with a total heat gain of 358±37 ZJ, which is equivalent to a global heating rate of 0.47±0.1 W m−2. Over the period 1971–2018 (2010–2018), the majority of heat gain is reported for the global ocean with 89 % (90 %), with 52 % for both periods in the upper 700 m depth, 28 % (30 %) for the 700–2000 m depth layer and 9 % (8 %) below 2000 m depth. Heat gain over land amounts to 6 % (5 %) over these periods, 4 % (3 %) is available for the melting of grounded and floating ice, and 1 % (2 %) is available for atmospheric warming. Our results also show that EEI is not only continuing, but also increasing: the EEI amounts to 0.87±0.12 W m−2 during 2010–2018. Stabilization of climate, the goal of the universally agreed United Nations Framework Convention on Climate Change (UNFCCC) in 1992 and the Paris Agreement in 2015, requires that EEI be reduced to approximately zero to achieve Earth's system quasi-equilibrium. The amount of CO2 in the atmosphere would need to be reduced from 410 to 353 ppm to increase heat radiation to space by 0.87 W m−2, bringing Earth back towards energy balance. This simple number, EEI, is the most fundamental metric that the scientific community and public must be aware of as the measure of how well the world is doing in the task of bringing climate change under control, and we call for an implementation of the EEI into the global stocktake based on best available science. Continued quantification and reduced uncertainties in the Earth heat inventory can be best achieved through the maintenance of the current global climate observing system, its extension into areas of gaps in the sampling, and the establishment of an international framework for concerted multidisciplinary research of the Earth heat inventory as presented in this study. This Earth heat inventory is published at the German Climate Computing Centre (DKRZ, www.dkrz.de, last access: 7 August 2020) under the DOI doi.org/10.26050/WDCC/GCOS_EHI_EXP_v2 (von Schuckmann et al., 2020).

Organisation(s)

Department of Meteorology and Geophysics

External organisation(s)

European Centre for Medium-Range Weather Forecasts (ECMWF), Mercator Ocean International, Chinese Academy of Sciences (CAS), Met Office, Columbia University in the City of New York, Weltorganisation für Meteorologie (WMO), UN, University of California, San Diego, St. Francis Xavier University, James J. Howard Marine Sciences Laboratory, Memorial University of Newfoundland, Institut français de recherche pour l'exploitation de la mer (IFREMER), National Oceanography Centre Southampton, University of Tasmania, Karl-Franzens-Universität Graz, Meteorological Research Institute - Japan Meteorological Agency, Universität Bremen, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Eidgenössische Technische Hochschule Zürich, University of Leeds, Yale University, Woods Hole Oceanographic Institution

Journal

Earth System Science Data

Volume

12

Pages

2013–2041

No. of pages

29

ISSN

1866-3508

DOI

https://doi.org/10.5194/essd-12-2013-2020

Publication date

09-2020

Peer reviewed

Yes

Austrian Fields of Science 2012

105204 Climatology, 105206 Meteorology

Keywords

Sustainable Development Goals

SDG 13 - Climate Action

Portal url

https://ucrisportal.univie.ac.at/en/publications/463a20e9-5ac8-4eab-bf8d-01328146124d