A recent study published last week in leading scientific journal Nature reveals that the natural weathering process of rocks may be contributing significant amounts of carbon dioxide (CO2) to the atmosphere, potentially on par with emissions from volcanoes.
This discovery challenges our understanding of the carbon cycle and its implications for climate change modeling, online magazine Popular Science commented.
While the concept of storing excess carbon in rocks as a climate change mitigation strategy has gained attention, it is not a straightforward solution.
Rocks can act as carbon sinks when certain minerals within them absorb CO2 during chemical weathering, countering the emissions from volcanoes.
However, the new study identifies an additional process in which rocks, primarily those thrust to the Earth’s surface during mountain-building events, can release CO2.
This release occurs when ancient seafloor rocks, containing organic carbon from long-deceased organisms, are exposed to oxygen and water upon reaching the Earth’s surface.
The carbon then reacts with oxygen, which results in CO2 being released into the atmosphere, turning these weathering rocks into sources of CO2 rather than carbon sinks.
To quantify this phenomenon, researchers used a tracer element called rhenium, which is released into water when organic carbon in rocks reacts with oxygen.
Their findings indicate that natural rock weathering of silicate materials releases approximately 68 megatons of CO2 per year, roughly equivalent to the emissions from heating and cooling buildings during extreme weather in the US in 2022.
“This is about 100 times less than present day human CO2 emissions by burning fossil fuels, but it is similar to how much CO2 is released by volcanoes around the world, meaning it is a key player in Earth’s natural carbon cycle”, study co-author and University of Oxford geochemist Professor Robert Hilton said in a statement.
The researchers note that these carbon release events may have varied throughout Earth’s history, potentially influencing global climate during periods of mountain formation.
Furthermore, they are investigating how human-caused climate changes and increased erosion could lead to an increase in this natural CO2 leak in the coming century.
“While the carbon dioxide release from rock weathering is small compared to present-day human emissions, the improved understanding of these natural fluxes will help us better predict our carbon budget”, Dr. Jesse Zondervan, who led the study at the Department of Earth Sciences at the University of Oxford, concluded.