Chains of volcanoes have helped to stabilise temperatures on Earth during its history, both emitting and removing carbon dioxide from the atmosphere, a new study has shown.
The researchers caution that nature will not "step in" to solve human-caused climate change, and our emissions are far greater than those caused by volcanoes.
But an artificial version of the "weathering" by which volcanoes remove CO2 from the atmosphere could become an important tool in battling climate change, they believe.
Natural breakdown and dissolution of rocks at Earth's surface is called chemical weathering.
Products of weathering (elements like calcium and magnesium) are flushed via rivers to the oceans, where they form minerals that lock up CO2.
This feedback mechanism regulates atmospheric CO2 levels (and the world’s climate) over long periods.
Dr Tom Gernon, associate professor in Earth science at the University of Southampton, says "In this respect, weathering of the Earth's surface serves as a geological thermostat. But the underlying controls have proven difficult to determine due to the complexity of the Earth system."
The team constructed a novel "Earth network", incorporating machine-learning algorithms and plate tectonic reconstructions to monitor how volcanoes have contributed to carbon on our planet.
The team found that continental volcanic arcs were the most important driver of weathering intensity over the past 400 million years.
Today, continental arcs comprise chains of volcanoes in, for example, the Andes in South America, and the Cascades in the US.
These volcanoes are some of the highest and fastest-eroding features on Earth. Because the volcanic rocks are fragmented and chemically reactive, they are rapidly weathered and flushed into the oceans.
Dr Gernon said: "Unfortunately, the results do not mean that nature will save us from climate change.
"Today, atmospheric CO2 levels are higher than at any time in the past 3 million years, and human-driven emissions are about 150 times larger than volcanic CO2 emissions.
"The continental arcs that appear to have saved the planet in the deep past are simply not present at the scale needed to help counteract present-day CO2 emissions."
Artificially enhanced rock weathering – where rocks are pulverised and spread across land to speed up chemical reaction rates – could play a key role in safely removing CO2 from the atmosphere.
The team's findings suggest that such schemes may be deployed optimally by using calc-alkaline volcanic materials (those containing calcium, potassium and sodium) like those found in continental arc environments.
Gernon said: "This is by no means a silver bullet solution to the climate crisis – we urgently need to reduce CO2 emissions in line with IPCC mitigation pathways, full stop.
"Our assessment of weathering feedbacks over long timescales may help in designing and evaluating large-scale enhanced weathering schemes, which is just one of the steps needed to counteract global climate change."
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