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Natural weathering processes are removing CO₂ from the air in a wide range of environments across continents and oceans. Until recently, these "CO₂ vacuum cleaners" were often studied separately, without properly examining their complex interactions.

Now, an international team of Earth scientists is proposing an integrated vision of the many factors that influence the removal of atmospheric CO₂ from the highest mountain peaks to the deep ocean floor, including their various interactions. The so-called weathering continuum provides a much more complete picture of what controls and regulates the natural removal of CO₂, which could help in the development of enhanced weathering techniques.

The type of rock worn away by wind and water, the chemical reactions that break down rocks and convert them into soils and muds: all of this influences the rate at which CO₂ is removed naturally from the air and is stored in the soils or the ocean. The efficiency of these CO₂ vacuum cleaners has varied substantially in Earth's past, which had researchers puzzled for over a century.

Weathering continuum

Viewing the numerous chemical reactions of minerals on land and in the ocean as a single entity鈥攁 weathering continuum鈥攏ow emerges from a new research paper, published in Nature Geoscience, involving numerous experts from various disciplines.

"The main conclusion from our work is that the various CO₂ fluxes on land and in the ocean are very closely linked. This governs the efficiency of the removal of CO₂ from the atmosphere," says Dr. Gerrit Trapp-M眉ller, a postdoctoral researcher at the Georgia Institute of Technology and the lead author of the study, which he did when he was still affiliated with Utrecht University.

Previous research had already shown that it is possible that the natural weathering processes can practically come to a halt鈥攁nd sometimes even reverse, when the ocean starts to emit CO₂.

"Using the analogy of the vacuum cleaner, if intense vacuum cleaning has already filled up the device's storage unit, it eventually becomes less effective in cleaning鈥攁nd may even blow out the dust back into your apartment."

Reducing greenhouse effect

Compared to emissions from human activities, the natural processes that remove CO₂ are relatively slow. Could this new research help us harness these natural CO₂ vacuums to reduce the still increasing amounts of greenhouse gases in the atmosphere?

"Enhanced weathering" technologies could help to get somewhere close to the 1.5 or 2.0掳C targets of the Paris Agreement, agrees Trapp-M眉ller.

But he also cautions, "If weathering accelerates in some place, it can have consequences for the rest of the chain and the net amount of carbon stored."

The weathering continuum warns of the unforeseen consequences of enhanced weathering sites, but also provides guidance on how to harness the full potential of these techniques.