Ocean heat content
Published (reviewed and quality assured)
Justification for indicator selection
The World Ocean is the dominant component of the Earth’s heat balance. Oceans cover roughly 72 % of the planet’s surface, and water has a heat uptake capacity that is around 20 times greater than that of the atmosphere. About 90 % of the total warming caused by climate change is manifested in increased global heat content. Hence, a precise estimate of Ocean Heat Content (OHC) is essential for understanding the role of oceans in past climate change, and for assessing future climate change. OHC is defined as the integrated temperature change times the density of sea water, times specific heat capacity from the surface down to the deep ocean. Estimates of it are made based on temperature measurements or on reanalyses made using a combination of models and observations.
Changes in heat content also cause the ocean to expand or contract, thereby changing sea level regionally and globally. This thermosteric effect has contributed about one quarter to global sea-level rise since 1993.
- IPCC, 2013. Climate Change: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change[Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.
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.
Key policy question
What is the trend in the heat content of the global ocean?
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
EEA data references
- No datasets have been specified here.
External data references
- Ocean heat content calculated based on observations made in the upper 700 m and 2000 m of the water column
Data sources in latest figures
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
Short term work
Work specified here requires to be completed within 1 year from now.
Long term work
Work specified here will require more than 1 year (from now) to be completed.
Responsibility and ownership
EEA Contact InfoTrine Christiansen
Frequency of updates
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)