Carbon dioxide levels in the atmosphere have risen an extra 15 parts per million since 1960 due to the declining ability of the land and sea to soak up excess CO2
By Michael Le Page
19 August 2025
Wildfires, like this one in Greece, are blunting Earth’s natural carbon sink
Thanassis Stavrakis/AP Photo/Alamy
Climate change is increasingly affecting the ability of Earth’s natural carbon sinks to soak up excess carbon dioxide, and this means more of this greenhouse gas emitted by human activity is staying in the atmosphere, leading to further warming.
These feedback effects are responsible for about 15 per cent of the increase in CO2 levels since 1960, according to Pierre Friedlingstein at the University of Exeter at the UK.
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The land and oceans have been acting as carbon sinks, soaking up nearly half of all the excess CO2 humans have been pumping out. For instance, higher CO2 can boost plant growth, meaning more CO2 is taken up by vegetation. But as the world warms, extreme heat, droughts and wildfires can increasingly counteract this CO2 fertilisation effect.
Friedlingstein is involved in the Global Carbon Project, which is trying to work out exactly how much CO2 is being emitted, how much is absorbed by various sources and how this is changing over time. He and his team had previously used climate models to estimate that the land sink would be taking up 27 per cent more CO2 were it not for feedbacks such as droughts.
Their latest estimate now puts it at 30 per cent, Friedlingstein told the Exeter Climate Conference last month. Meanwhile, the ocean sink would be taking up 6 per cent more CO2 were it not for feedbacks, he said.