The ocean is struggling to breathe as it absorbs our excess heat and carbon

Science · Published 7 October 2026 Swipe more like this →

In short: The world's oceans act as a massive planetary regulator, absorbing 90% of excess heat and a quarter of human-caused CO2. However, this vital service is under threat. As waters warm and acidify, the very mechanisms that keep our climate stable may begin to fail, creating a dangerous feedback loop.

The ocean's capacity to regulate the climate relies on its role as a primary carbon reservoir, storing approximately 38,000 billion tonnes of carbon. By absorbing about 23% of human-caused CO2 emissions, the oceans mitigate the pace of global warming. However, scientists are concerned that as anthropogenic CO2 emissions continue, these carbon sequestration routes could shift from being a sink to becoming a source, potentially accelerating climate change.

Since 1970, the ocean's mean temperature has been climbing at a mean rate of 0.11°C every decade. This warming triggers thermal expansion—where seawater becomes less dense and expands—which has been responsible for over one-third of observed sea level rise in recent decades. Additionally, melting ice sheets in Greenland and Antarctica pose a significant threat to global sea levels, while melting sea ice reduces the planet's albedo, or ability to reflect sunlight, leading to further warming.

Beyond temperature, the chemistry of the sea is changing. As more CO2 dissolves in the water, the ocean becomes more acidic, a process that can weaken the external skeletons of corals and the shells of mollusks and crustaceans. These shifts disrupt ocean currents, such as the Atlantic Meridional Overturning Circulation (AMOC), which redistribute heat and nutrients. Such disruptions threaten marine ecosystems, from Arctic algae to coral reefs, and could ultimately impact the food security of billions of people and coastal communities worldwide.

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