Deep Carbon Observatory quantifies carbon emissions

The DCO revealed that volcanoes and volcanic regions emit 0.28 to 0.36 gigtonnes (Gt) of CO₂ per year. This compares to around 9.9 Gt of carbon emitted per year by human activity[i], through the burning of fossil fuels and forests.

“Today, the flux of anthropogenically-generated carbon, primarily from burning of fossil fuels that formed over millions of years, is contributing to a major perturbation to the carbon cycle,” the DCO’s findings from a 10-year study, published as a series of papers in Elements, reads.

“In order to understand the possible effects of this perturbation, there is a need for scientists to understand other catastrophic perturbations in Earth's history and to evaluate the sources and sinks of carbon in the Earth system.”

DCO has provided a total estimate of 1.85 billion Gt of carbon on Earth, about 0.2% of which – 43,500 Gt – is above the surface, in oceans, on land and in the atmosphere.

Around 37,000 Gt, or 85.1%, of this above-surface carbon is in the deep ocean; 6.9% is in marine sediments; 4.6% in the terrestrial biosphere; 2% in the surface ocean; and 1.4% in the atmosphere.

Over millions of years, the quantity of carbon emissions from mountain belts and tectonic plate boundaries has been fairly balanced with carbon returned to below Earth’s surface through subduction and other processes.

However, about four times over the past 500 million years this balance has been upended by the emergence of large volcanic events that degassed enormous volumes of carbon – up to 30,000 Gt or around 70% of today’s estimated 43,500 Gt above-surface carbon.

Such a carbon cycle imbalance can cause rapid global warming, changes to the silicate weathering rate, changes to the hydrologic cycle and overall rapid habitat changes that can cause mass extinction as the Earth rebalances itself.

Rice University geologist Cin Ty Lee said: “For billions of years, Earth seems to have found a balance between carbon subducted deep into the interior and carbon emitted from volcanoes – processes that help to stabilize climate and environment.

“But how stable is that incessant cycling? No natural law requires that the amount of carbon going down must exactly equal the carbon returned to the surface by volcanoes and other less violent means.

“No question is more central to the Deep Carbon Observatory than this balance between what goes down and what comes back up.”

The Deep Carbon Observatory, established in 2009, is a community of more than 1,000 scientists who share research on the Earth’s carbon composition.

The DCO will summarise the 10-year program and launch the next decade of deep carbon science at the National Academy of Sciences in Washington DC from October 24-26.

[i] le Quere and al., 2016

Read our interview with Robert H. Hazen, Executive Director of the Deep Carbon Observatory