Posted on 09/20/2003 9:43:49 PM PDT by PeaceBeWithYou
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.
This story has been adapted from a news release issued by Virginia Tech.
It's Bush's fault.
They'll brush it off.
"Well, no one likes to look backwards. We have to think of today.
Right now, what really concerns us the most is the future.
As we progress into our future, we have so many more tasks to accomplish in order to insure a safe planet for our worlds children.
Now, as we progress, there's a few things I'd like to discuss today. As you all know, the United States, the largest producer of toxic gasses, has refused to accept........."
Ancient Relatives Of Algae Yield New Insights Into Role Of CO2 In Earth's Early AtmosphereArlington, Va. -- Awareness of the global warming effects of carbon dioxide (CO2) is relatively recent, but the greenhouse gas has been playing a critical role in warming our planet for billions of years, according to University of Maryland geologist Jay Kaufman and Virginia Polytechnic Institute geologist Shuhai Xiao.
Their results, which provide the best evidence to date of the age of the Calvin cycle--the photosynthetic cycle by which plants convert light energy and CO2 into cellular tissue--will be published in the September 18 issue of the journal Nature.
The research was funded by the National Science Foundation (NSF), an independent federal agency that supports fundamental research and education across all fields of science and engineering, and by NASA.
"This research is solid indirect evidence of the very high level of atmospheric CO2 at about 1,4000 million years ago, " says Enriqueta Barrera, program director in NSF's division of earth sciences.
Using samples taken from individual fossils of an ancient relative of algae, Kaufman and Xiao provide the first estimates of the concentration of CO2 in the atmosphere some 1.4 billion years ago. Their study results show that the CO2 concentration at that time was 10 to 200 times higher than today's levels. The gas therefore likely played a major role in keeping Earth warm, and probably dominated over another greenhouse gas, methane, after the atmosphere and oceans became oxygenated between 2 billion and 2.2 billion years ago.
"The sun was not as luminous then so it did not provide as much light and heat as it does now," said Kaufman. "Our new findings confirm models of how much greenhouse gas was required to keep Earth's temperature warm enough so the oceans didn't freeze during this time."
The Proterozoic period--the time period examined by Kaufman and Xiao--began 2.5 billion years ago and ended 543 million years ago. Scientists think many of the far-reaching events in the evolutionary history of our planet occurred during that period, including the appearance of abundant living organisms (probably early single- and multi-celled organisms) and significant oxygen in the atmosphere.
One of the ocean-dwelling organisms producing oxygen during the later Proterozoic period was Dictyosphaera delicata, a microscopic plant not much bigger than the dot in the letter i. To estimate ancient levels of atmospheric CO2, Kaufman and Xiao measured ratios of two different forms, or isotopes, of carbon present in individual microfossils of this plant.
"It was a painstaking process to get individual organisms," Kaufman said. The scientists "were able to take a camel hair brush and, using one hair of the brush, pick up one of these microfossils, which had been removed from its substrate [rock] using hydrofluoric acid, which dissolves the inorganic minerals but not organic matter."
Numerous microscopic samples of fossilized cellular material were knocked out of each organism using high-energy beams of ions from an ion probe. The sample material was analyzed with a mass spectrometer to come up with the results reported.
Kaufman is known for his contributions to research indicating that Earth has been almost entirely covered in ice several times within the last billion years. Kaufman and other scientists believe that each of these "snowball earth" periods were ended by a warming of the Earth resulting from a buildup in the atmosphere of greenhouse gases, particularly carbon dioxide.
Editor's Note: The original news release can be found here.
Are they still employed?
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Global Temperature and Atmospheric CO2 over Geologic Time
Late Carboniferous to Early Permian time (315 mya -- 270 mya) is the only time period in the last 600 million years when both atmospheric CO2 and temperatures were as low as they are today (Quaternary Period ). Temperature after C.R. Scotese
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