Ironclad? Analyses of rocks in an ancient Greenland formation debunk the idea of an early greenhouse Earth.
Credit: M. Rosing
Posted on 04/04/2010 8:02:57 AM PDT by neverdem
Dial back the clock nearly 4 billion years, to a time called the Archean, and the sun would appear about 30% dimmer than it is now. That's a problem: It couldn't have warmed Earth enough to keep the seas from becoming permanent ice sheets. Yet overwhelming geological evidence indicates that liquid water has existed on our planet since the seas formed more than 4 billion years ago, even during the deepest ice ages. What could have provided the added warmth?
In 1972, famed astronomer Carl Sagan proposed that the answer lay in the atmosphere. Sagan and his co-author George Mullen hypothesized that carbon dioxide (CO2) concentrations were much higher during the Archean—possibly 100 times higher than they are today—and therefore the atmosphere could retain enough heat to keep the planet from freezing. But so far, no one has found convincing data that Earth was once a super greenhouse. And now researchers have uncovered strong evidence to the contrary.
A team led by earth scientist Minik Rosing of the University of Copenhagen analyzed iron-bearing rocks in southwestern Greenland that were 3.8 billion years old. They focused on two minerals, magnetite and siderite, that can provide a bellwether of the CO2 concentrations in the atmosphere. Too much CO2, and magnetite can't form, whereas the opposite is true for siderite. Based on the ratio of the minerals, the team reports in tomorrow's issue of Nature that CO2 levels during the Archean could have been no higher than about 1000 parts per million—about three times the current level of 387 ppm and not high enough to compensate for the weak sun.
The results were "very surprising," Rosing says. As to the question of what kept the planet warm instead of CO2, he says his research points to two possibilities. First, Earth's land masses were much smaller billions of years ago, meaning that the oceans, which generally are darker than continents, could absorb more of the sun's heat. Second, because life was brand new, organisms were manufacturing little of the gases that help clouds form. So, more sunlight reached the surface.
There are bound to be other factors, Rosing says. "I think that our paper is just one link in a long chain of further refinements of our understanding of the early Earth and of the dynamics of our planet."
Earth scientist James Kasting of Pennsylvania State University, University Park, thinks it's premature to discard the greenhouse-gas option. Temperatures during the Archean were at least as high as they are today, despite the weaker sun, he says. It's difficult to account for the warmth using just the mechanisms suggested in this paper, Kasting says. "So, I think there is still a need for additional greenhouse gases."
The Competitive Enterprise Institute will be bestowing the Julian Simon Award on Steve McIntyre and Ross McKitrick for their efforts in debunking Mann's hockey stick at CEI's 2010 Dinner, June 17 at Hyatt Regency Capitol Hill 400 New Jersey Ave. NW Washington, DC 20001.
Wouldn’t earth 4 billion years ago have been quite a bit warmer on the inside? Like a pie fresh out of the oven? That would have made the crust warmer as well.
What keeps Earth's interior warm is radioactive decay ~ the current proposal is that thorium is the main source, but there are other possibilities ~ maybe even a natural uranium reactor at the central part of the core!
Gortex.
Why don’t we put Al Gore in Professor Peabody’s “Way Back Machine” and send him back four million years and let him investigate.
Not to mention the fact that there was far more volcanism going on at the time.
An additional greenhouse effect would not have been enough to keep the Earth from turning into a complete iceball.
There had to be lower Albedo (reflectance of sunlight) by clouds / atmospheric gases as well.
ping
Only if we can leave him there.
LLS
But how did God bring that about?
It’s possible that iron was in heavier abundances during early solar system history (especially in its inner parts) and that it formed Earth’s, and other terrestrial planetary cores early on. That, with radiogenics also settling out, may have provided enough heat for this not only on Earth, but also on Mars which seems to have had an abundance of early water on its surface as well.
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Thanks neverdem.Dial back the clock nearly 4 billion years, to a time called the Archean, and the sun would appear about 30% dimmer than it is now. That's a problem: It couldn't have warmed Earth enough to keep the seas from becoming permanent ice sheets. Yet overwhelming geological evidence indicates that liquid water has existed on our planet since the seas formed more than 4 billion years ago, even during the deepest ice ages.To all -- please ping me to other topics which are appropriate for the GGG list. |
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Early Water on Earth
Geotimes | February 2003 | Salma Monani
Posted on 02/09/2003 7:22:57 PM EST by CalConservative
http://www.freerepublic.com/focus/news/839466/posts
Early Earth Likely Had Continents, Was Habitable, According To New Study
University of Colorado at Boulder | 2005-11-18 | University of Colorado at Boulder
Posted on 11/18/2005 11:32:59 PM EST by dila813
http://www.freerepublic.com/focus/news/1525001/posts
Sea floor records ancient Earth
BBC | Friday, 23 March 2007, 09:09 GMT
Jonathan Fildes Science and technology reporter, BBC News
Posted on 03/24/2007 2:06:03 AM EDT by Ernest_at_the_Beach
http://www.freerepublic.com/focus/news/1805973/posts
Crusty Old Discovery Reveals Early Earth’s History
(3.8 billion years old outer crust)
LiveScience.com on yahoo | 3/24/07 | Robert Roy Britt
Posted on 03/24/2007 10:40:45 PM EDT by NormsRevenge
http://www.freerepublic.com/focus/news/1806290/posts
Diamonds Tell Story Of Earth’s Beginning
The Telegraph (UK) | 8-22-2007 | Roger Highfield
Posted on 08/22/2007 9:48:58 PM EDT by blam
http://www.freerepublic.com/focus/news/1885157/posts
http://www.marxists.org/reference/subject/philosophy/works/us/gaia.htm
Life first appeared on the Earth about 3,500 million years ago. From that time until now, the presence of fossils shows that the Earth’s climate has changed very little. Yet the output of heat from the sun, the surface properties of the Earth, and the composition of the atmosphere have almost certainly varied greatly over the same period.
The chemical composition of the atmosphere bears no relation to the expectations of steady-state chemical equilibrium. The presence of methane, nitrous oxide, and even nitrogen in our present oxidising atmosphere represents violation of the rules of chemistry to be measured in tens of orders of magnitude. Disequilibria on this scale suggest that the atmosphere is not merely a biological product, but more probably a biological construction: not living, but like a cat’s fur, a bird’s feathers, or the paper of a wasp’s nest, an extension of a living system designed to maintain a chosen environment. Thus the atmospheric concentration of gases such as oxygen and ammonia is found to be kept at an optimum value from which even small departures could have disastrous consequences for life.
The climate and the chemical properties of the Earth now and throughout its history seem always to have been optimal for life. For this to have happened by chance is as unlikely as to survive unscathed a drive blindfold through rush-hour traffic.
Source: Gaia A new look at life on Earth by J E Lovelock, publ. Oxford University Press 1979.
...the presence of fossils shows that the Earth’s climate has changed very little...
Even today, I think that if it were not for the internal heat of the Earth, we would freeze over - the amount of sunlight we receive is not enough to stop it.
http://www.ucmp.berkeley.edu/precambrian/archaean.html
I see no mention in this article of the other greenhouse gases; namely methane, ammonia or water vapor.
The solar models also have a lot of variability. They predict the sun was anywhere from 30% to 75% less bright. Maybe they’re wrong.
all he did was prove what an idiot he was.
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