Even if humans stop emitting greenhouse gases, the ocean would begin releasing the heat it has accumulated for decades.
The Southern Ocean has long served as one of the climate buffers most vital areas on Earth, absorbing enormous amounts of heat and carbon dioxide generated by human activity.
But a new paper published in AGU Advances suggests that once greenhouse gas emissions finally decline, this ocean safety net could trigger a warming wave powerful and prolonged.
Researchers at the Helmholtz GEOMAR Center for Ocean Research in Germany used a comprehensive climate modeling framework to simulate a long term scenario: Greenhouse gas emissions continue to rise for approximately another 70 years, until atmospheric CO₂ levels double, after which emissions decline rapidly and global temperatures begin to cool over several centuries.
But even with the drop in atmospheric CO₂, models show that the ocean continues to absorb heat for many years. This happens because surface temperatures drop slowly and because the Southern Ocean, already warm and free of sea ice, becomes more efficient in absorbing solar radiation, losing less heat to the atmosphere.
After centuries of cooling, the system reaches a tipping point. The deep ocean begins to release stored heat like a “burp”, driving a new peak in global temperatures that has lasted for a century. Lead author Ivy Frenger describes the phenomenon as global atmospheric warming “not related to CO₂ emissions”, but rather caused by the delayed release of ocean heat. The projected rate of warming is comparable to increases caused by human action over the past century.
In practice, the buffer capacity of the Southern Ocean is temporary and its eventual reversal could prolong the climate crisis long after emissions have reached negative levels. Warming will likely be unevenly distributed, with the strongest and most persistent impacts falling on the Southern Hemisphere. Many of the countries most vulnerable to climate change are located in this region, which increases concerns about the amplification of inequalities, says the .
These simulations suggest that even if humanity rapidly reduces emissions, the climate system could continue to warm for centuries due to feedback effects stored in the deep ocean. The authors warn that the models represent simplified scenarios, but similar results across different modeling approaches reinforce the conclusion.
