Human activity churns out up to 100 times more carbon each year as all volcanoes, according to a decade-long study that also estimated the entire amount of the element on Earth.

The Deep Carbon Observatory, a 500-strong international team of scientists, released a series of papers outlining how carbon is stored, emitted and reabsorbed by natural and man-made processes.

They found that human carbon dioxide emissions drastically outstrip the contribution of volcanoes – which belch out gas and are often fingered as a major climate change contributor – to current warming rates.

The findings, published in the journal Elements, showed just 0.2 percent of Earth’s total carbon is above the surface in oceans, the land, and in our atmosphere.

The rest – a staggering 1.85 billion billion tonnes – is stored in our planet’s crust, mantle and core, providing scientists with clues as to how Earth formed billions of years ago.

By measuring the prominence of certain carbon isotopes in rock samples around the world, the scientists were able to create a timeline stretching back 500 million years to map how carbon moved between land, sea and air.

They found that in general the planet self-regulated atmospheric levels of carbon dioxide, a key greenhouse gas, over geological timeframes of hundreds of thousands of years.

The exceptions to this came in the form of “catastrophic disturbances” to Earth’s carbon cycle, such as immense volcanic eruptions or the meteor strike that killed off the dinosaurs.

“In the past we see that these big carbon inputs to the atmosphere cause warming, cause huge changes in both the composition of the ocean and the availability of oxygen,” said Marie Edmonds, Professor of Volcanology and Petrology and Ron Oxburgh Fellow in Earth Sciences at Queens’ College, Cambridge.

The team estimated that the Chicxulub impact 66 million years ago, which killed off three-quarters of all life on Earth, released between 425 and 1,400 billion tonnes of CO2.

Man-made emissions in 2018 alone topped 37 billion tonnes.

“The amount of CO2 pumped into the atmosphere by anthropogenic [manmade] activity in the last 10 to 12 years is equivalent to the catastrophic change during these events we’ve seen in Earth’s past,” Edmonds said. (AFP)