Ocean heat content
- The warming of the World Ocean accounts for approximately 93 % of the warming of the Earth system during the last 6 decades.
- An increasing trend in the heat content in the uppermost 700 m depth of the World Ocean is evident over the last 6 decades. Recent observations show substantial warming also of the deeper ocean (between 700 m and 2 000 m depth).
- Further warming of the oceans is expected with projected climate change, but quantitative projections of ocean heat content are not available.
What is the trend in the heat content of the global ocean?
Ocean heat content calculated based on observations made in the upper 700 m of the water column
Note: Ocean heat content is defined as the integrated temperature change times the density of seawater, times specific heat capacity from the surface down to the deep ocean.
- Ocean heat content calculated based on observations made in the upper 700 m and 2000 m of the water column provided by National oceanic and atmospheric administration (NOAA)
The warming of the World Ocean accounts for approximately 90 % of the warming of the Earth during the last 6 decades [i].
Figure 1 shows that the heat content of the World Ocean has increased since around 1970. The linear trend over the whole time series 1955–2010 of the uppermost 700 m and 2 000 m layer was 0.27 Wm-2 and 0.39 Wm-2 (per unit area of the World Ocean), respectively. Two thirds of the observed increase of global heat content has occurred in the upper 700 m of the ocean, with increases in the layers below 700 m depth accounting for the remaining one third [ii]. Heat content has increased in all major sea basins of the World Ocean, in particular in the Atlantic Ocean.
Several global ocean data assimilation products are available to compare observation-based estimates with independent reanalysis data. Global and basin-scale heat content warming trends in the upper 700 m of the ocean computed from a set of global ocean reanalyses fall within the range of the most recent observation-based estimates derived using different methods [iii].
Projections of OHC are very uncertain and are hence not included here.
[i] John A. Church et al., „Revisiting the Earth’s sea-level and energy budgets from 1961 to 2008“, Geophysical Research Letters 38, Nr. 18 (September 16, 2011), doi:10.1029/2011GL048794; J. Hansen et al., „Earth’s energy imbalance and implications“, Atmospheric Chemistry and Physics 11, Nr. 24 (Dezember 22, 2011): 13421–13449, doi:10.5194/acp-11-13421-2011; S. Levitus et al., „World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010“, Geophysical Research Letters 39, Nr. 10 (Mai 17, 2012), doi:10.1029/2012GL051106.
[ii] J.E. Dore et al., „Physical and biogeochemical modulation of ocean acidification in the central North Pacific“, Proceedings of the National Academy of Sciences 106 (2009): 12235–12240., doi:10.1073/pnas.0906044106; S. Levitus u. a., „Global ocean heat content 1955–2008 in light of recently revealed instrumentation problems“, Geophysical Research Letters 36, Nr. 7 (April 11, 2009), doi:10.1029/2008GL037155; Levitus et al., „World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010“; Sarah G. Purkey and Gregory C. Johnson, „Warming of global abyssal and deep southern ocean waters between the 1990s and 2000s: Contributions to global heat and sea level rise budgets“, Journal of Climate 23, Nr. 23 (Dezember 2010): 6336–6351, doi:10.1175/2010JCLI3682.1.
[iii] John M. Lyman et al., „Robust warming of the global upper ocean“, Nature 465, Nr. 7296 (Mai 2010): 334–337, doi:10.1038/nature09043; Simona Masina u. a., „Global ocean re-analyses for climate applications“, Dynamics of Atmospheres and Oceans 52, Nr. 1–2 (September 2011): 341–366, doi:10.1016/j.dynatmoce.2011.03.006.
Indicator specification and metadata
Observed change in global ocean heat content
Ocean heat content (Joule)
Policy context and targets
In April 2013 the European Commission presented the EU Adaptation Strategy Package (http://ec.europa.eu/clima/policies/adaptation/what/documentation_en.htm). This package consists of the EU Strategy on adaptation to climate change /* COM/2013/0216 final */ and a number of supporting documents. One of the objectives of the EU Adaptation Strategy is Better informed decision-making, which should occur through Bridging the knowledge gap and Further developing Climate-ADAPT as the ‘one-stop shop’ for adaptation information in Europe. Further objectives include Promoting action by Member States and Climate-proofing EU action: promoting adaptation in key vulnerable sectors. Many EU Member States have already taken action, such as by adopting national adaptation strategies, and several have also prepared action plans on climate change adaptation.
The European Commission and the European Environment Agency have developed the European Climate Adaptation Platform (Climate-ADAPT, http://climate-adapt.eea.europa.eu/) to share knowledge on observed and projected climate change and its impacts on environmental and social systems and on human health; on relevant research; on EU, national and subnational adaptation strategies and plans; and on adaptation case studies.
No targets have been specified.
Related policy documents
Climate-ADAPT: Mainstreaming adaptation in EU sector policies
Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored
Climate-ADAPT: National adaptation strategies
Overview of activities of EEA member countries in preparing, developing and implementing adaptation strategies
DG CLIMA: Adaptation to climate change
Adaptation means anticipating the adverse effects of climate change and taking appropriate action to prevent or minimise the damage they can cause, or taking advantage of opportunities that may arise. It has been shown that well planned, early adaptation action saves money and lives later. This webportal provides information on all adaptation activities of the European Commission.
EU Adaptation Strategy Package
In April 2013 the European Commission adopted an EU strategy on adaptation to climate change which has been welcomed by the EU Member States. The strategy aims to make Europe more climate-resilient. By taking a coherent approach and providing for improved coordination, it will enhance the preparedness and capacity of all governance levels to respond to the impacts of climate change.
Methodology for indicator calculation
Ocean heat content is defined as the integrated temperature change times the density of seawater, times specific heat capacity from the surface down to the deep ocean. It is calculated here base on observations from the upper 700 metres of ocean water.
The warming of the world ocean since 1955 is estimated using different kinds of observational data: historical data not previously available, additional modern data, correcting for instrumental biases of bathythermograph data, and correcting or excluding some Argo float data.
Methodology for gap filling
- Levitus et al. 2012: World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010 S. Levitus, J. I. Antonov, T. P. Boyer, O. K. Baranova, H. E. Garcia, R. A. Locarnini, A. V. Mishonov, J. R. Reagan, D. Seidov, E. S. Yarosh and M. M. Zweng (2012): World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010. Geophysical Research Letters 39(10). doi:10.1029/2012GL051106
Data sets uncertainty
Ocean temperature data are sparse in the polar and subpolar regions of the world. In general, however, changes related to the physical and chemical marine environment are better documented than biological changes because links between cause and effect are better understood and often time series of observations are longer. For example, systematic observations of both sea-level and sea surface temperature were started around 1880 and are today complemented by observations from space that have high resolution in time and geographical coverage and by Argo floats that also automatically measure temperature and salinity below the ocean surface.
Further information on uncertainties is provided in Section 1.7 of the EEA report on Climate change, impacts, and vulnerability in Europe 2012 (http://www.eea.europa.eu/publications/climate-impacts-and-vulnerability-2012/)
No uncertainty has been specified
Ocean heat content calculated based on observations made in the upper 700 m and 2000 m of the water column
provided by National oceanic and atmospheric administration (NOAA)
Climate change (Primary topic)
Coasts and seas
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CLIM 044
Contacts and ownership
EEA Contact InfoTrine Christiansen
EEA Management Plan2012 2.0.1 (note: EEA internal system)
Frequency of updates
For references, please go to www.eea.europa.eu/soer or scan the QR code.
This briefing is part of the EEA's report The European Environment - State and Outlook 2015. The EEA is an official agency of the EU, tasked with providing information on Europe's environment.
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