Climate Change Feedback Loops Are Degrading Earth’s Carbon Sinks

Climate change is increasingly compromising the ability of the Earth’s natural carbon sinks to absorb excess carbon dioxide. This results in greenhouse gases emitted by human activity lingering in the atmosphere, contributing to further warming.

These feedback loops account for roughly 15% of the rise in CO2 levels since 1960, according to Pierre Friedlingstein from the University of Exeter, UK.

The land and oceans serve as carbon sinks, absorbing nearly half of the extra CO2 produced by humans. While higher CO2 levels can enhance plant growth, leading to greater CO2 uptake by vegetation, extreme temperatures, droughts, and wildfires associated with global warming can counteract this CO2 fertilization effect.

Friedlingstein is part of the Global Carbon Project, which aims to clarify the amounts of CO2 being emitted, how it is absorbed by different sources, and how this process evolves over time. Previously, his research team used climate models to project a 27% increase in land sinks in the absence of drought or other feedbacks.

His latest estimates have adjusted this figure to 30%, as he shared at the Exeter Climate Conference last month. He mentioned that ocean sinks also increase CO2 by 6% without feedback effects.

Together, land and oceans contribute over 15% of atmospheric CO2. Since 1960, CO2 levels have surged to around 100 parts per million (ppm), indicating that 15 ppm can be traced back to the feedback effects impacting the sinks. “The sink hasn’t collapsed, but its recovery is slow,” Friedlingstein noted.

There remains uncertainty regarding the sink’s capacity, as David Armstrong McKay from the University of Sussex has observed. “It aligns with expectations, but it’s not encouraging news that we’re marginally off what we projected,” McKay stated. “As warming intensifies, it will challenge land sinks’ adaptability to increased CO2, with extreme events like the recent El Niño-enhanced drought hampering the positive effects on vegetation growth.”

The pressing question is what will unfold next. With the rise in warming, droughts, and fires, research has indicated that land sinks have made minimal net CO2 contributions in the past two years.

This has raised concerns that the effectiveness of land sinks might significantly decrease in the near future, opposing the gradual decline most climate scientists anticipate.

Nonetheless, Friedlingstein referred to these short-term fluctuations as “blips” that may not accurately predict future trends. “What we should focus on is the long term,” he emphasized.