UN warns warming is weakening the ocean’s ability to absorb carbon
A new UN-backed assessment says climate change has already reduced the ocean’s capacity to absorb carbon by approximately six percent, raising concerns ahead of COP31.
Photo credit and license
Photo: Buckshop / Wikimedia Commons, CC BY 4.0; contextual photograph (February 2026). · Image source · License: CC BY 4.0A report highlighted by the United Nations on 29 October 2026 warns that the ocean is becoming less effective at absorbing carbon as the planet warms. The assessment, prepared through cooperation between the UN Environment Programme and the UN climate secretariat, says climate change has already reduced ocean carbon-absorption capacity by approximately six percent.
The ocean plays a central role in slowing global warming. It absorbs around 30 percent of carbon dioxide emissions caused by human activity and about 90 percent of the excess heat trapped by greenhouse gases, according to the UN. Those functions have come under increasing strain as temperatures rise.
Warmer water, changes in ocean chemistry, shifts in circulation and damage to marine ecosystems can affect how carbon moves between the atmosphere, the surface and deeper waters. If the sea absorbs a smaller share of emissions, more carbon dioxide may remain in the atmosphere, compounding pressure on the climate.
The estimate is a warning about a changing planetary system, not a claim that the ocean has stopped taking up carbon. The strength of this natural sink varies by region and over time, and projections depend on how emissions and ocean conditions evolve.
The report arrived ahead of the COP31 climate conference in November. Its central message is that reducing greenhouse-gas emissions remains essential, while improved monitoring and protection of marine ecosystems can help researchers and governments understand the changes already under way.
