Atmospheric carbon dioxide greater 1.4 billion years ago

September 17, 2003

(Blacksburg, Va., September 18, 2003) -- Billions of years ago, there was a lot more greenhouse gas than today, and that was a good thing - else the Earth might be an icy ball.

How much greenhouse gas was there in the ancient atmosphere? A 1993 model by Jim Kasting of Pennsylvania State University estimates that carbon dioxide (CO2) levels in the Earth's early atmosphere must have been 10 times to as much as 10,000 times today's level, in order to compensate for the young (and fainter) sun. Now, a measurement of the fossil record using a new instrument has confirmed a portion of the model. Atmospheric CO2 level 1.4 billion years ago was at least ten to 200 times greater than today, according to the new research.

The findings are reported in the September 18, 2003, issue of Nature by Alan Jay Kaufman of the geology department at the University of Maryland and Shuhai Xiao of the geosciences department at Virginia Tech ("High CO2 levels in the Proterozoic atmosphere estimated from analyses of individual microfossils").

The researchers determined the CO2 level by using the carbon ion microprobe housed at the Carnegie Institute in Washington, D.C. They conducted their studies on the microscopic fossil Dictyosphaera delicata from Proterozoic shales in northern China. "This was a eukaryotic photosynthesizer - it had a nucleus and made organic matter from CO2 - about one-tenth of a millimeter in size," says Xiao. "It had the ability to become dormant in bad times, when it formed a robust wall to protect itself. That tough wall is what is preserved in the fossil record."

All modern eukaryotic photosynthesizers use a similar biochemical pathway to convert CO2 into organic matter. "We assume the old guy used the same biochemical pathway," says Xiao. Therefore, they would be able to measure the type of carbon in the fossil in order to determine the CO2 concentrations in the ocean and the atmosphere.

"We zapped into the fossil using a 10 micrometer ion beam, which destroys a small amount of the organic material and ejects carbon ions, which we analyzed," says Xiao.

The critical measure was the amount of carbon-12 (12C) versus carbon-13 (13C). D. delicata formed their organic wall from dissolved CO2 in the ocean. Carbon dioxide formed with 12C is preferred because it is lighter. The higher ratio of 12C in the tissue would indicate higher levels of CO2 available in the water. Since D. delicata lived in the surface ocean, which is at equilibrium with the atmosphere, the amount of CO2 in the atmosphere could also be calculated.

Carbon dioxide today is 350 parts per million (ppm) or .035 percent - compared to 270 ppm before industrialization - a less than 30 percent increase. But 1.4 billion years ago, CO2 was more than 10 to 200 times today's level.

"This gives us a geological context for CO2 evolution and climate change," says Xiao. While Kaufman and Xiao's study confirms the model, "We need more data points to fill the gaps and test the model for the first four billion years," Xiao says.

There are many data points to confirm the model from the last half billion years, but the Kaufman and Xiao study provide only the second data point between a half billion years ago and 4.5 billion years ago. Rob Rye at University of Southern California and colleagues looked at ancient soil from 2.7 billion years ago and determined there was barely enough CO2 to compensate for the weaker Sun - the lowest range of the Kasting model. "But there were probably significant amounts of other greenhouse gases, such as methane, 2.7 billion years ago," says Xiao.

The Earth's atmosphere became more oxidized by 2.2 billion years ago, after which methane became a less significant greenhouse gas, "But, by the period of our study, there was plenty of CO2," says Xiao.
Xiao and Kaufman began their collaboration at Harvard, where Kaufman was a post-doctoral associate while Xiao was a graduate student. The research was supported by NASA Exobiology, NSF Geology and Paleontology, and China Ministry of Science and Technology 973 programs. Xiao was a faculty member at Tulane University before joining the Virginia Tech faculty this fall.

Contact Dr. Xiao at 540-231-1366 or or Dr. Kaufman at 301-405-0395 or

There is also an article on this research in the News and Notes section of Nature and a University of Maryland news release with information from Dr. Kaufman will be available on that university's web site once the embargo lifts.

Virginia Tech

Related Climate Change Articles from Brightsurf:

Are climate scientists being too cautious when linking extreme weather to climate change?
Climate science has focused on avoiding false alarms when linking extreme events to climate change.

Mysterious climate change
New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past.

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.

Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.

Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.

Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.

A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).

Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.

Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.

Read More: Climate Change News and Climate Change Current Events 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