Ice age thermostat prevented extreme climate cooling

March 14, 2017

Atmospheric CO2 concentrations swung over a range of 100 ppm (parts per million, by volume) during the ice ages. The exact processes behind this variation have been difficult to pinpoint, but it is known that changes in the storage of carbon by photosynthetic organisms played an important role.

"When we took a close look at measurements from ice cores, we noticed that atmospheric CO2 concentrations hovered close to 190 ppm during much of the past 800,000 years, but very rarely fell any lower," said Sarah Eggleston, a researcher at the Institut of Environmental Science and Technology (ICTA-UAB) and co-author of the study. "This was surprising, because it suggests that these very low CO2 concentrations were quite stable. What's more, we know that CO2 was often very high in the distant geological past, but we have no evidence that CO2 concentrations were ever lower than 190 ppm."

"We know that, over hundreds of thousands of years, CO2 is regulated by slowly reacting with exposed rocks" explained Eric Galbraith, lead author of the study and an ICREA professor at ICTA-UAB. "But this would be too slow to explain the stability during periods of only a few thousand years, as we see in the ice cores. So it must have been some other mechanism that kicked in at very low CO2."

The authors suggest that it was most likely the biosphere that maintained habitable temperatures, since at very low CO2 levels, plants and phytoplankton struggle to photosynthesize. Slower growth of these organisms would have meant less carbon in the soils and deep ocean leaving more in the atmosphere, and preventing CO2 concentrations from falling further. This might have prevented extreme cooling that would have led to Earth freezing over as a 'snowball'.

However, the study did not reveal a corresponding regulation during the warm portions of the ice age cycles, suggesting that the Earth does not have a similar mechanism to prevent rapid warming.
-end-


Universitat Autonoma de Barcelona

Related Carbon Articles from Brightsurf:

The biggest trees capture the most carbon: Large trees dominate carbon storage in forests
A recent study examining carbon storage in Pacific Northwest forests demonstrated that although large-diameter trees (21 inches) only comprised 3% of total stems, they accounted for 42% of the total aboveground carbon storage.

Carbon storage from the lab
Researchers at the University of Freiburg established the world's largest collection of moss species for the peat industry and science

Carbon-carbon covalent bonds far more flexible than presumed
A Hokkaido University research group has successfully demonstrated that carbon-carbon (C-C) covalent bonds expand and contract flexibly in response to light and heat.

Metal wires of carbon complete toolbox for carbon-based computers
Carbon-based computers have the potential to be a lot faster and much more energy efficient than silicon-based computers, but 2D graphene and carbon nanotubes have proved challenging to turn into the elements needed to construct transistor circuits.

Cascades with carbon dioxide
Carbon dioxide (CO(2)) is not just an undesirable greenhouse gas, it is also an interesting source of raw materials that are valuable and can be recycled sustainably.

Two-dimensional carbon networks
Lithium-ion batteries usually contain graphitic carbons as anode materials. Scientists have investigated the carbonic nanoweb graphdiyne as a novel two-dimensional carbon network for its suitability in battery applications.

Can wood construction transform cities from carbon source to carbon vault?
A new study by researchers and architects at Yale and the Potsdam Institute for Climate Impact Research predicts that a transition to timber-based wood products in the construction of new housing, buildings, and infrastructure would not only offset enormous amounts of carbon emissions related to concrete and steel production -- it could turn the world's cities into a vast carbon sink.

Investigation of oceanic 'black carbon' uncovers mystery in global carbon cycle
An unexpected finding published today in Nature Communications challenges a long-held assumption about the origin of oceanic black coal, and introduces a tantalizing new mystery: If oceanic black carbon is significantly different from the black carbon found in rivers, where did it come from?

First fully rechargeable carbon dioxide battery with carbon neutrality
Researchers at the University of Illinois at Chicago are the first to show that lithium-carbon dioxide batteries can be designed to operate in a fully rechargeable manner, and they have successfully tested a lithium-carbon dioxide battery prototype running up to 500 consecutive cycles of charge/recharge processes.

How and when was carbon distributed in the Earth?
A magma ocean existing during the core formation is thought to have been highly depleted in carbon due to its high-siderophile (iron loving) behavior.

Read More: Carbon News and Carbon Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.