How much of global warming heat does the ocean absorb?

The ocean has taken up the large majority of the excess heat trapped in the climate system, far more than the atmosphere or land, which is why ocean heat content is a key indicator of global warming.

Will the ocean keep absorbing carbon dioxide indefinitely?

The ocean continues to absorb carbon, but its efficiency declines as surface waters warm and their chemistry becomes more saturated, so it cannot be relied upon to keep pace with rising emissions.

Ocean Heat and Carbon Uptake

The ocean has absorbed the overwhelming majority of the heat trapped by greenhouse gases and roughly a quarter of human carbon emissions, buffering the climate at the cost of warming, acidifying, and rising seas.

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Definition

Ocean heat and carbon uptake is the absorption and storage by the ocean of excess heat from the enhanced greenhouse effect and of carbon dioxide emitted by human activities, which together moderate the rate of climate change.

Scope

This topic covers the ocean's storage of heat and the measurement of ocean heat content, the air-sea exchange and interior storage of anthropogenic carbon dioxide, the physical and biological processes that draw heat and carbon into the deep ocean, and the implications and limits of the ocean as a climate buffer.

Core questions

How much of the planet's excess heat and human carbon emissions does the ocean absorb?
What processes carry heat and carbon from the surface into the deep ocean?
How is ocean heat content and the carbon sink measured and tracked?
What are the consequences and limits of the ocean's role as a climate buffer?

Key theories

Ocean as the dominant heat reservoir: Because water has a large heat capacity and the ocean is vast, it stores the great majority of the energy added to the climate system, so ocean heat content is the most reliable measure of global warming.
The oceanic carbon sink: Air-sea exchange and circulation carry a substantial fraction of anthropogenic carbon dioxide into the ocean interior, a sink quantified by basin-scale carbon surveys.

Mechanisms

Heat and carbon dioxide enter the ocean at the surface and are carried into the interior by mixing, subduction of surface waters, and the overturning circulation, while the biological pump adds to carbon storage. The large heat capacity and volume of the ocean let it absorb most of the climate system's excess energy, but uptake slows as surface waters warm and saturate with carbon.

Clinical relevance

Ocean heat and carbon uptake set the pace of surface warming and the size of the airborne fraction of emissions; they also drive ocean warming, acidification, deoxygenation, and thermal sea-level rise, making their monitoring central to tracking and projecting climate change.

History

Revelle and Suess showed in 1957 that the ocean takes up carbon dioxide but more slowly than its volume alone suggests; sustained observations, the global carbon survey synthesized by Sabine and colleagues in 2004, and the Argo float array have since quantified the ocean's heat and carbon uptake with growing precision.

Key figures

Roger Revelle
Christopher Sabine
Nicolas Gruber

Seminal works

sarmientoGruber2006
sabine2004

Frequently asked questions

How much of global warming heat does the ocean absorb?: The ocean has taken up the large majority of the excess heat trapped in the climate system, far more than the atmosphere or land, which is why ocean heat content is a key indicator of global warming.
Will the ocean keep absorbing carbon dioxide indefinitely?: The ocean continues to absorb carbon, but its efficiency declines as surface waters warm and their chemistry becomes more saturated, so it cannot be relied upon to keep pace with rising emissions.