Scientists estimate Earth's total carbon store (DCO)

[Gordon_R]

https://www.bbc.com/news/science-environment-49899039

There are 1.85 billion, billion tonnes of carbon on Earth, with more than 99% of it resident beneath our feet.

Scientists from the Deep Carbon Observatory (DCO) project have spent 10 years assessing the "reservoirs and fluxes" of the chemical element.

In other words, they worked out where carbon is held and in what form, and how it moves through the Earth system.

The findings will help understand the limits of life on our planet and in the forecasting of volcanic eruptions.

"This work really came out of the realisation that much of the carbon that we are concerned about for climate change is only a tiny fraction of our planet's carbon. More than 90% of it is actually in the interior of the Earth - in the crust, in the mantle and the core," said Prof Marie Edmonds from Cambridge University, UK.

"Very little was known about its form, how much there was, and how mobile it is. And, obviously, this all has huge importance for both the climate of the Earth, but also the habitability of our surface environment," the DCO collaborator told BBC News.

The accounting was a painstaking process that included monitoring gas emissions from major volcanoes and examining the deep-sea muds that are drawn, or subducted, into the Earth's interior at tectonic plate boundaries.

Through the use of lab experiments and models, the team was then able to simulate the likely stores and flows of carbon.

Just two-tenths of 1% of Earth's total carbon - about 43,500 billion tonnes - is judged to be above the planet's surface, in the oceans, on land, and in the atmosphere. Everything else is in the deep reservoir, with two-thirds of the total contained within the core.

In a fascinating exercise, the DCO attempted to describe how this inventory has changed through time. Working with the University of Sydney, it has reconstructed the history of plate tectonics - to in effect replay the movie of the Earth's inner workings.

This revealed that the planet's carbon budget through much of the last billion years has been in a relatively steady state. Put another way, the carbon that has been drawn down into the Earth's interior is roughly equal to what has been outgassed to the atmosphere through the likes of volcanoes.

Every now and then, however, there have been major catastrophic perturbations in this cycle.

These disturbances were the result of asteroid impacts or prolonged, large-scale volcanism that put substantial volumes of carbon dioxide into the atmosphere - leading to warming, acidified oceans, and even mass extinctions.

The suspicion, of course, is that we are now in another of these great perturbations.

Over the past 100 years, carbon emissions from human activities such as through the burning of fossil fuels have been 40 to 100 times greater than our planet's geologic carbon emissions.

"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 pervious catastrophic carbon events," said Dr Celina Suarez from the University of Arkansas

"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."

 

[Gordon_R]

Background reading: https://en.wikipedia.org/wiki/Deep_Carbon_Observatory

In 2007, Robert Hazen, a Senior Staff Scientist at the Carnegie Institution’s Geophysical Laboratory (Washington, DC, USA) spoke at the Century Club in New York, on the origins of life on Earth and how geophysical reactions may have played a critical role in the development of life on Earth. Jesse Ausubel, a faculty member at Rockefeller University and Program Director at the Alfred P. Sloan Foundation, was in attendance and later sought out Hazen's book, Genesis: The Scientific Quest for Life’s Origins.

After two years of planning and collaboration, Hazen and colleagues officially launched the Deep Carbon Observatory (DCO) in August 2009, with its secretariat based at the Geophysical Laboratory of the Carnegie Institution of Washington, DC. Hazen and Ausubel, along with input from over 100 scientists invited to participate in the Deep Carbon Cycle Workshop in 2008, expanded their original idea. No longer focused solely on the origin of life on Earth, the group instead clarified their position to further human understanding of Earth, carbon, that critical element, had to take center stage.

 

[Zoomzoom]

Human ancestors not to blame for ancient mammal extinctions in Africa

New research disputes a long-held view that our earliest tool-bearing ancestors contributed to the demise of large mammals in Africa over the last several million years. Instead, the researchers argue that long-term environmental change drove the extinctions, mainly in the form of grassland...

phys.org

New research disputes a long-held view that our earliest tool-bearing ancestors contributed to the demise of large mammals in Africa over the last several million years. Instead, the researchers argue that long-term environmental change drove the extinctions, mainly in the form of grassland expansion likely caused by falling atmospheric carbon dioxide (CO2) levels.

"The key factor in the Plio-Pleistocene megaherbivore decline seems to be the expansion of grasslands, which is likely related to a global drop in atmospheric CO2 over the last five million years," says John Rowan, a postdoctoral scientist from University of Massachusetts Amherst. "Low CO2 levels favor tropical grasses over trees, and as a consequence savannas became less woody and more open through time. We know that many of the extinct megaherbivores fed on woody vegetation, so they seem to disappear alongside their food source."

Low CO2 bad. High CO2 good! CO2 makes plants GROW!!!!