While volcanoes and other natural processes release 0.28 to 0.36 gigatonnes of carbon dioxide per year, DCO said, human activity released more than 37 gigatonnes in 2018 alone, according to AFP. In total, annual human emissions are 40 to 100 times greater than those of volcanoes, DCO explained in a press release.

"Climate sceptics really jump on volcanoes as a possible contender for top CO2 emissions but it's simply not the case," Professor of Volcanology and Petrology and Ron Oxburgh Fellow in Earth Sciences at Queens' College, Cambridge Marie Edmonds told AFP.

The studies didn't just focus on anthropogenic carbon releases. They provided a general account of where all of the Earth's carbon is stored and how it moves through the environment, as BBC News explained. What they found is that the vast majority of Earth's 1.85 billion gigatonnes of carbon is below ground, with two thirds in the core. Only 43,500 billion tonnes (approximately 47,951 U.S. tons) are above ground in the oceans, land and atmosphere. This represents just two-tenths of one percent of Earth's carbon.

The researchers also investigated geological history in order to understand how carbon has moved through the Earth's systems over time. They found that, for the most part over the past 500 million years, the planet has drawn down as much carbon into the ground as it has released, maintaining balance. However, there were a few notable exceptions, as Eos explained:

In the past 500 million years, four volcanic eruptions created large igneous provinces (LIPs) that each released massive quantities of CO2 over tens of thousands of years. These LIPs caused the above-ground quantity of CO2 to spike to about 170% of its steady state value, which led to warmer surface conditions, more acidic oceans, and mass extinctions.

Likewise, large impact events, including the Chicxulub impact 65 million years ago, released large quantities of carbon from the subsurface into the atmosphere.

The Chicxulub impact is the event that likely drove the dinosaurs to extinction, and what's worrying is that human activity is actually releasing carbon dioxide at a slightly higher rate today, Eos reported.

"It's really revealing that the amount of carbon dioxide we're emitting in a short time period is very close to the magnitude of those previous catastrophic carbon events," Dr. Celina Suarez from the University of Arkansas told BBC News. "A lot of those ended in mass extinctions, so there are good reasons why there is discussion now that we might be in a sixth mass extinction."

While Earth's systems did eventually rebalance after past catastrophic carbon releases, that did not happen quickly.

"Climate deniers always say that Earth always rebalances itself," Suarez told AFP. "Well, yes it has. It will rebalance itself, but not on a timescale that is of significance to humans."

While the research is another sobering reminder of the severity of the climate crisis, it did uncover some potentially life-saving information: Volcanoes often discharge certain gasses before they erupt.

"A shift in the composition of volcanic gases from smelly (akin to burnt matches) sulphur dioxide (SO2) to a gas richer in odorless, colorless CO2 can be sniffed out by monitoring stations or drones to forewarn of an eruption—sometimes hours, sometimes months in advance," DCO explained. "Eruption early warning systems with real-time monitoring are moving ahead to exploit the CO2 to SO2 ratio discovery, first recognized with certainty in 2014."