For over a century, the Southern Ocean has served as a crucial buffer, silently absorbing vast amounts of carbon dioxide and heat produced by human activity. This process has delayed the most severe effects of global warming , helping to stabilise Earth’s climate. Yet, new research suggests this balance may not last. Scientists warn that once humanity significantly reduces fossil fuel emissions, the Southern Ocean could release its stored heat in a massive ‘burp,’ reversing progress and reigniting global warming. This delayed release, potentially lasting more than a century, highlights how the ocean’s hidden processes could continue to influence the planet’s temperature long after carbon emissions fall, complicating efforts to restore climate stability.
Scientists warn the Southern Ocean could release trapped heat after emissions stop
According to a new study by German climate scientists, when global greenhouse gas emissions finally reach net zero and the planet begins to cool, the Southern Ocean is expected to unleash an enormous and sudden release of trapped heat. This event could temporarily reverse any progress made in cooling the planet.
The prediction arises from a well-established climate modelling framework that integrates data on atmospheric energy and moisture balance, ocean circulation, sea ice dynamics, land biosphere, and ocean biochemistry. By simulating an idealised future scenario, the researchers examined how the Earth’s systems might respond to centuries of emissions followed by rapid decarbonisation.
How the Southern Ocean traps and later releases hidden heat
In the model, human activity continues to drive greenhouse gas emissions for roughly 70 more years until carbon dioxide levels double. Then, either through human innovation or an unforeseen collapse in emissions, global output sharply declines. Over several centuries, net-negative emissions lead to gradual planetary cooling.
However, even as the atmosphere begins to cool, the ocean continues to absorb heat for some time. This is because the surface temperature of the atmosphere decreases slowly, and deep ocean layers remain insulated from rapid changes. Furthermore, as sea ice melts, the ocean absorbs more solar radiation since the reflective white surface that once bounced sunlight back into space is greatly reduced.
During the warming phase, heat accumulates deep within the ocean. This occurs partly because warmer surface waters sink and mix with cooler layers below, distributing heat throughout the depths. Before industrialisation, the Southern Ocean naturally lost heat through upwelling currents that brought cold water to the surface. However, climate change has disrupted this circulation, trapping more heat beneath the surface.
When the surface eventually cools, this stored heat does not simply disappear. Instead, it is gradually released back into the atmosphere, a process that Frenger and her team describe as a “global atmospheric warming unrelated to CO₂ emissions.”
The Southern Ocean’s heat ‘burp’ could trigger another century of global warming
Lead researcher Dr Ivy Frenger of the GEOMAR Helmholtz Centre for Ocean Research explained that this delayed release of heat could cause global temperatures to rise again at rates comparable to the warming experienced during the industrial era. This secondary warming phase could last more than a century, meaning that even after achieving negative emissions, humanity might still face a prolonged period of rising temperatures.
Their model visualises this as a clear “burp” phase—a grey-shaded section in temperature projections showing renewed warming after centuries of cooling.
The effects of this oceanic heat release would not be evenly spread across the planet. According to the study, the most severe and persistent warming would occur in the Southern Hemisphere. This poses particular risks for nations in the global south, many of which are already more vulnerable to climate-related disasters such as droughts, extreme storms, and food insecurity.
Southern Ocean heat release may delay global cooling
The researchers emphasise that these findings question a key assumption in global climate policy that the amount of CO₂ emitted directly correlates with long-term warming. If the Southern Ocean releases stored heat long after emissions fall, then the benefits of climate action may take far longer to materialise than anticipated.
Also Read | Astronauts reveal how a matchstick burns in space and why its flame turns into a floating blue sphere
Scientists warn the Southern Ocean could release trapped heat after emissions stop
According to a new study by German climate scientists, when global greenhouse gas emissions finally reach net zero and the planet begins to cool, the Southern Ocean is expected to unleash an enormous and sudden release of trapped heat. This event could temporarily reverse any progress made in cooling the planet.
The prediction arises from a well-established climate modelling framework that integrates data on atmospheric energy and moisture balance, ocean circulation, sea ice dynamics, land biosphere, and ocean biochemistry. By simulating an idealised future scenario, the researchers examined how the Earth’s systems might respond to centuries of emissions followed by rapid decarbonisation.
How the Southern Ocean traps and later releases hidden heat
In the model, human activity continues to drive greenhouse gas emissions for roughly 70 more years until carbon dioxide levels double. Then, either through human innovation or an unforeseen collapse in emissions, global output sharply declines. Over several centuries, net-negative emissions lead to gradual planetary cooling.
However, even as the atmosphere begins to cool, the ocean continues to absorb heat for some time. This is because the surface temperature of the atmosphere decreases slowly, and deep ocean layers remain insulated from rapid changes. Furthermore, as sea ice melts, the ocean absorbs more solar radiation since the reflective white surface that once bounced sunlight back into space is greatly reduced.
During the warming phase, heat accumulates deep within the ocean. This occurs partly because warmer surface waters sink and mix with cooler layers below, distributing heat throughout the depths. Before industrialisation, the Southern Ocean naturally lost heat through upwelling currents that brought cold water to the surface. However, climate change has disrupted this circulation, trapping more heat beneath the surface.
When the surface eventually cools, this stored heat does not simply disappear. Instead, it is gradually released back into the atmosphere, a process that Frenger and her team describe as a “global atmospheric warming unrelated to CO₂ emissions.”
The Southern Ocean’s heat ‘burp’ could trigger another century of global warming
Lead researcher Dr Ivy Frenger of the GEOMAR Helmholtz Centre for Ocean Research explained that this delayed release of heat could cause global temperatures to rise again at rates comparable to the warming experienced during the industrial era. This secondary warming phase could last more than a century, meaning that even after achieving negative emissions, humanity might still face a prolonged period of rising temperatures.
Their model visualises this as a clear “burp” phase—a grey-shaded section in temperature projections showing renewed warming after centuries of cooling.
The effects of this oceanic heat release would not be evenly spread across the planet. According to the study, the most severe and persistent warming would occur in the Southern Hemisphere. This poses particular risks for nations in the global south, many of which are already more vulnerable to climate-related disasters such as droughts, extreme storms, and food insecurity.
Southern Ocean heat release may delay global cooling
The researchers emphasise that these findings question a key assumption in global climate policy that the amount of CO₂ emitted directly correlates with long-term warming. If the Southern Ocean releases stored heat long after emissions fall, then the benefits of climate action may take far longer to materialise than anticipated.
Also Read | Astronauts reveal how a matchstick burns in space and why its flame turns into a floating blue sphere
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