Earths natural weathering system removes millions of tons CO2

Natural processes on land and in the ocean already remove carbon dioxide from the air, but they do not work in isolation. A new paper argues that these processes must be seen as one connected system, a weathering continuum that stretches from high terrain to the deepest seabed and controls how much CO2 is locked away over time.

This perspective matters because many climate ideas aim to speed up weathering to pull more CO2 from the atmosphere. If the pieces of the chain are tightly linked, pushing on one part can tug on another in ways that help or hurt the total carbon removed.

Why linking land and ocean matters

Dr. Gerrit Trapp-Müller of the Georgia Institute of Technology led the study, which was completed during his time at Utrecht University.

The team brings reactions in soils, rivers, coasts, and marine sediments into one model so we can view the whole system, not just scattered parts.

In this framework, the direction and size of a local flux depend on the material’s origin, how it has been transported and altered, and the surrounding conditions. That is a practical shift, because it changes how we should place, size, and verify interventions meant to boost carbon removal.

How silicate weathering stores CO2

At the center is silicate weathering – the set of reactions where acidic water breaks down silicate minerals, releasing cations and bicarbonate that ultimately store carbon as carbonate minerals.

Over geologic time, silicate weathering acts as a negative feedback that steadies climate by consuming more CO2 as temperatures rise.

This thermostat effect is real but slow on human timescales. It scales with factors such as temperature, runoff, rock type, and how quickly fresh mineral surfaces are exposed.

Oceans can release CO2

There is a twist called reverse weathering. In marine sediments, the formation of authigenic clays can consume alkalinity, release acidity, and shift carbon back toward the atmosphere.

When reactions that consume alkalinity dominate parts of the chain, the net sink can shrink or even flip. That means the ocean side of the system can throttle what the land side achieves.

Not all settings pull equal weight. Recent work highlights deltas and beaches as marine weathering hotspots that can shape the balance between forward and reverse reactions along the transport path from rivers to the shelf and beyond.

Studies in delta muds, using both field data and models, show that where the sediment comes from and how it was deposited determine whether chemical reactions add or remove alkalinity – and by how much – at different depths and over time. These factors decide whether the area is a strong sink or only a weak one.

How much CO2 weathering removes

So how much carbon does chemical weathering handle today. A global analysis finds total CO2 consumption by chemical weathering near 237 million metric tons of carbon per year, with silicates accounting for roughly 63 percent of that budget, on the order of 149 million tons of carbon annually.

Within the silicate share, basaltic terrains have an outsized impact, contributing on the order of 25 to 35 percent of the silicate weathering CO2 sink because they weather quickly where runoff is high.

That concentration of flux in a small fraction of the landscape explains why placement of interventions matters so much.

How we could boost weathering

Analyses suggest that spreading finely crushed silicate rock on croplands could remove on the order of 0.5 to 2.0 billion tons of CO2 per year, comparable to other land-based options if done at scale and with the right logistics.

This is a large range, and it depends on climate, soils, farm practices, and supply chains.

Recent evaluations also warn that removal efficiency varies widely and can be overestimated if you ignore side fluxes, carbonate dynamics, or downstream processes in the ocean that offset gains on land. Measuring the whole chain is not optional, it is the only way to know the real net.

The future of weathering research

“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,” said Trapp-Müller.

Treating weathering as one system forces three practical habits. Site selection should consider downstream coupling, monitoring must track products beyond the field edge, and models need to include both forward and reverse reactions across environments.

Future studies may map which river basins, coastlines, and sedimentary settings deliver the biggest net gains once ocean processes are included. That includes quantifying how fast material moves along the conveyor from hills to seabed and how reaction balances change en route.

The new perspective also invites better stress tests for proposed projects, from agricultural basalt applications to coastal alkalinity additions, against the actual carbon accounting of the full chain. 

The study is published in the journal Nature Geoscience.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–