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

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, https://www.dkrz.de/, last access: 7 August 2020) under the DOI https://doi.org/10.26050/WDCC/GCOS_EHI_EXP_v2 (von Schuckmann et al., 2020)

Heat stored in the Earth system 1960–2020: where does the energy go?

The Earth climate system is out of energy balance, and heat has accumulated continuously over the past decades, warming the ocean, the land, the cryosphere, and the atmosphere. According to the Sixth Assessment Report by Working Group I of the Intergovernmental Panel on Climate Change, this planetary warming over multiple decades is human-driven and results in unprecedented and committed changes to the Earth system, with adverse impacts for ecosystems and human systems. The Earth heat inventory provides a measure of the Earth energy imbalance (EEI) and allows for quantifying how much heat has accumulated in the Earth system, as well as where the heat is stored. Here we show that the Earth system has continued to accumulate heat, with 381±61 ZJ accumulated from 1971 to 2020. This is equivalent to a heating rate (i.e., the EEI) of 0.48±0.1 W m−2. The majority, about 89 %, of this heat is stored in the ocean, followed by about 6 % on land, 1 % in the atmosphere, and about 4 % available for melting the cryosphere. Over the most recent period (2006–2020), the EEI amounts to 0.76±0.2 W m−2. The Earth energy imbalance is the most fundamental global climate indicator that the scientific community and the public can use as the measure of how well the world is doing in the task of bringing anthropogenic climate change under control. Moreover, this indicator is highly complementary to other established ones like global mean surface temperature as it represents a robust measure of the rate of climate change and its future commitment. We call for an implementation of the Earth energy imbalance into the Paris Agreement's Global Stocktake based on best available science. The Earth heat inventory in this study, updated from von Schuckmann et al. (2020), is underpinned by worldwide multidisciplinary collaboration and demonstrates the critical importance of concerted international efforts for climate change monitoring and community-based recommendations and we also call for urgently needed actions for enabling continuity, archiving, rescuing, and calibrating efforts to assure improved and long-term monitoring capacity of the global climate observing system. The data for the Earth heat inventory are publicly available, and more details are provided in Table 4.</p

Formation of large sulfide mineral deposits along fast spreading ridges. Example from off-axial deposits at 12°43′N on the East Pacific Rise

Submersible investigations with Nautile near the 13°N hydrothermal field on the EPR were made in 1992. We selected diving areas based on deep towed side scan sonar imaging. Close to a pit-crater at the top of a young seamount 2 km east of the axial ridge we discovered one of the largest (70 m high and 200 m in diameter) sulfide mounds formed at a fast spreading ridge (12 cm/yr). Despite an overlap in composition between axial and off-axial deposits the general trend reflects real differences in compositions. Off-axis deposit differs from axial deposits by the scarcity of zinc sulfides and cobalt and selenium enrichment. Sulfur isotope variation is minimal for the off-axis seamounts and suggests that sulfides precipitated from unmodifed end-member hydrothermal solutions. Axial sulfides have a broader range due to reduction of seawater sulfate at mixing fronts between hydrothermal and seawater solutions along the axial graben fault system. Lead isotopic compositions of sulfides are in two overlapping but distinct fields indicating different Pb sources and separate convective systems for the seamount and the axial deposits. Our observations suggest that the plumbing system is stable and centred on a shallow localised magma chamber under the seamount. This configuration is by far more efficient than unstable axial processes to create, during several hydrothermal episodes, major sulfide deposits near a fast spreading ridge. Off-axis seamounts are localised areas with high magmatic budget able to drive and focus hydrothermal systems at the same place for a long time. Other known occurrences of sulfides related to seamounts are at less than 11 km from the ridge axis. Thus we suggest that off-axial volcanoes close to the ridge are first order targets to discover active or inactive large deposits along fast- to medium-spreading ridges

Model derived uncertainties in deep ocean temperature trends between 1990-2010 (dataset)

Dataset for plotting the figures in the Garry et al. (2019) article "Model derived uncertainties in deep ocean temperature trends between 1990-2010" published in the Journal of Geophysical Research: Oceans. Requires Python 2.7.The article associated with this dataset is located in ORE at: http://hdl.handle.net/10871/35491We construct a novel framework to investigate the uncertainties and biases associated with estimates of deep ocean temperature change from hydrographic sections, and demonstrate this framework in an eddy-permitting ocean model. Biases in estimates from observations arise due to sparse spatial coverage (few sections in a basin), low frequency of occupations (typically 5-10 years apart), mismatches between the time period of interest and span of occupations, and from seasonal biases relating to the practicalities of sampling during certain times of year. Between the years 1990 and 2010, the modeled global abyssal ocean biases are small, although regionally some biases (expressed as a heat flux into the 4000 - 6000 m layer) can be up to 0.05 W/m². In this model, biases in the heat flux into the deep 2000 - 4000 m layer, due to either temporal or spatial sampling uncertainties, are typically much larger and can be over 0.1 W/m² across an ocean. Overall, 82% of the warming trend deeper than 2000 m is captured by hydrographic section-style sampling in the model. At 2000 m, only half the model global warming trend is obtained from observational-style sampling, with large biases in the Atlantic, Southern and Indian Oceans. Biases due to different sources of uncertainty can have opposing signs and differ in relative importance both regionally and with depth, revealing the importance of reducing temporal and spatial uncertainties in future deep ocean observing design.Natural Environment Research CouncilEuropean Research Counci

Model derived uncertainties in deep ocean temperature trends between 1990-2010 (dataset)

Dataset for plotting the figures in the Garry et al. (2019) article "Model derived uncertainties in deep ocean temperature trends between 1990-2010" published in the Journal of Geophysical Research: Oceans. Requires Python 2.7.The article associated with this dataset is located in ORE at: http://hdl.handle.net/10871/35491We construct a novel framework to investigate the uncertainties and biases associated with estimates of deep ocean temperature change from hydrographic sections, and demonstrate this framework in an eddy-permitting ocean model. Biases in estimates from observations arise due to sparse spatial coverage (few sections in a basin), low frequency of occupations (typically 5-10 years apart), mismatches between the time period of interest and span of occupations, and from seasonal biases relating to the practicalities of sampling during certain times of year. Between the years 1990 and 2010, the modeled global abyssal ocean biases are small, although regionally some biases (expressed as a heat flux into the 4000 - 6000 m layer) can be up to 0.05 W/m². In this model, biases in the heat flux into the deep 2000 - 4000 m layer, due to either temporal or spatial sampling uncertainties, are typically much larger and can be over 0.1 W/m² across an ocean. Overall, 82% of the warming trend deeper than 2000 m is captured by hydrographic section-style sampling in the model. At 2000 m, only half the model global warming trend is obtained from observational-style sampling, with large biases in the Atlantic, Southern and Indian Oceans. Biases due to different sources of uncertainty can have opposing signs and differ in relative importance both regionally and with depth, revealing the importance of reducing temporal and spatial uncertainties in future deep ocean observing design.Natural Environment Research CouncilEuropean Research Counci