Researcher unravels one of geology's great mysteries

Mar 31, 2010

Danish researcher has solved one of the great mysteries of our geological past: Why the Earth's surface was not one big lump of ice four billion years ago when sun radiation was much weaker than today. Scientists have presumed that the Earth's atmosphere back then consisted of 30 percent CO2 trapping heat like a greenhouse. However, new research shows that the reason for Earth not going into a deep freeze at the time was quite different.

In 1972, the late, world famous astronomer Carl Sagan and his colleague George Mullen formulated "The faint early sun paradox. " The paradox consisted in that the earth's climate has been fairly constant during almost four of the four and a half billion years that the planet has been in existence, and this despite the fact that radiation from the sun has increased by 25-30 percent.

The paradoxical question that arose for scientists in this connection was why the earth's surface at its fragile beginning was not covered by ice, seeing that the sun's rays were much fainter than they are today. Science found one probable answer in 1993, which was proffered by the American , Jim Kasting. He performed that showed that 30% of the earth's atmosphere four billion years ago consisted of CO2. This in turn entailed that the large amount of greenhouse gases layered themselves as a protective greenhouse around the planet, thereby preventing the oceans from freezing over.

Mystery solved

Now, however, Professor Minik Rosing, from the Natural History Museum of Denmark, and Christian Bjerrum, from the Department of Geography and Geology at University of Copenhagen, together with American colleagues from Stanford University in California have discovered the reason for "the missing ice age" back then, thereby solving the sun paradox, which has haunted scientific circles for more than forty years.

Professor Minik Rosing explains, "What prevented an ice age back then was not high CO2 concentration in the atmosphere, but the fact that the cloud layer was much thinner than it is today. In addition to this, the earth's surface was covered by water. This meant that the sun's rays could warm the oceans unobstructed, which in turn could layer the heat, thereby preventing the earth's watery surface from freezing into ice. The reason for the lack of clouds back in earth's childhood can be explained by the process by which clouds form. This process requires chemical substances that are produced by algae and plants, which did not exist at the time. These chemical processes would have been able to form a dense layer of clouds, which in turn would have reflected the sun's rays, throwing them back into the cosmos and thereby preventing the warming of earth's oceans. Scientists have formerly used the relationship between the radiation from the sun and earth's surface temperature to calculate that ought to have been in a during three billion of its four and a half billion years of existence. Sagan and Mullen brought attention to the paradox between these theoretical calculations and geological reality by the fact that the oceans had not frozen. This paradox of having a faint sun and ice-free oceans has now been solved."

CO2 history iluminated

Minik Rosing and his team have by analyzing samples of 3.8-billion-year-old mountain rock from the world's oldest bedrock, Isua, in western Greenland, solved the "paradox".

But more importantly, the analyses also provided a finding for a highly important issue in today's climate research - and climate debate, not least: whether the atmosphere's CO2 concentration throughout earth's history has fluctuated strongly or been fairly stable over the course of billions of years.

"The analyses of the CO2-content in the atmosphere, which can be deduced from the age-old Isua rock, show that the atmosphere at the time contained a maximum of one part per thousand of this . This was three to four times more than the atmosphere's CO2-content today. However, not anywhere in the range of the of the 30 percent share in early earth history, which has hitherto been the theoretical calculation. Hence we may conclude that the atmosphere's CO2-content has not changed substantially through the billions of years of earth's geological history. However, today the graph is turning upward. Not least due to the emissions from fossil fuels used by humans. Therefore it is vital to determine the geological and atmospheric premises for the prehistoric past in order to understand the present, not to mention the future, in what pertains to the design of climate models and calculations," underscores Minik Rosing.

Professor Rosing's scientific research has made its mark internationally on several earlier occasions, including research on the point in time when the first fragile life appeared and the impact of life's presence on the formation of the earth's landmass.

Explore further: Earthquakes occur in 4 parts of Alaska

Provided by University of Copenhagen

4 /5 (23 votes)

Related Stories

The rise of oxygen caused Earth's earliest ice age

May 07, 2009

(PhysOrg.com) -- Geologists may have uncovered the answer to an age-old question - an ice-age-old question, that is. It appears that Earth's earliest ice ages may have been due to the rise of oxygen in Earth's ...

More oxygen -- colder climate

Sep 10, 2009

Everybody talks about CO2 and other greenhouse gases as causes of global warming and the large climate changes we are currently experiencing. But what about the atmospheric and oceanic oxygen content? Which role does oxyge ...

Plants Save the Earth from an Icy Doom (w/ Podcast)

Jul 01, 2009

(PhysOrg.com) -- Fifty million years ago, the North and South Poles were ice-free and crocodiles roamed the Arctic. Since then, a long-term decrease in the amount of CO2 in the atmosphere has cooled the Earth. ...

Critical turning point can trigger abrupt climate change

Apr 20, 2009

Ice ages are the greatest natural climate changes in recent geological times. Their rise and fall are caused by slight changes in the Earth's orbit around the Sun due to the influence of the other planets. But we do not know ...

Recommended for you

User comments : 5

Adjust slider to filter visible comments by rank

Display comments: newest first

PinkElephant
3.8 / 5 (4) Mar 31, 2010
Oh boy... First, these guys claim to deduce global atmospheric CO2 levels from a sample of bedrock. WTF? Bedrock doesn't come in contact with the atmosphere, as a general rule...

Next, these guys completely neglect the rather obvious: earlier in Earth's history, both volcanism and orbital bombardment had to have been much more wide-spread and violent. This would've pumped copious amounts of aerosols and dust into the atmosphere, probably more than compensating for absence of wide-spread plant-life. Not to mention, volcanic aerosols in themselves have a pronounced atmospheric cooling effect, even in the absence of clouds...

Then, they completely ignore the overall heat flux through the Earth's surface, as the mantle and core continue to cool. Today's heat flux must necessarily be much lower than it was 4 billion years ago -- when it heated both the oceans and the atmosphere accordingly.

Then, consider catastrophically larger tides, due to low-orbiting moon...
ormondotvos
1 / 5 (2) Mar 31, 2010
I'm waiting for your peer-reviewed paper. Until then, I'll just assume you're another armchair denialist.
vidar_lund
2 / 5 (2) Apr 01, 2010
Next, these guys completely neglect the rather obvious: earlier in Earth's history, both volcanism and orbital bombardment had to have been much more wide-spread and violent...

Then, they completely ignore the overall heat flux through the Earth's surface, as the mantle and core continue to cool. Today's heat flux must necessarily be much lower than it was 4 billion years ago -- when it heated both the oceans and the atmosphere accordingly...


Well, I'm sure these guys know a couple of things about the earths geological history. Atmospheric content can to some extent be estimated through analysis of sedimentary bedrock and gases trapped in the rocks. Regarding the bombardment of the earth it had already stopped at this time and the heat from the earth would not have been much bigger than it is now. Much of the internal heat comes from radiative processes and not mechanical effects such as meteor strikes or tide.
out7x
5 / 5 (2) Apr 01, 2010
Deducing CO2 content in the Isua rocks is a stretch of the imagination. How about the radioactivity caused heat flow in the early earth.
PinkElephant
5 / 5 (2) Apr 01, 2010
@vidar_lund,
Atmospheric content can to some extent be estimated through analysis of sedimentary bedrock and gases trapped in the rocks.
Even IF the bedrock they examined was at some point sedimentary, at 3.8 billion years of age you can bet it's been metamorphosed to such an extent that any gas content signal has long since been garbled.
Regarding the bombardment of the earth it had already stopped at this time
It's still ongoing. It's not a binary process; it tapers off exponentially. Early in Earth's history, its orbit was still filled with a lot of rocky junk and dust, which has been continuously "raining out" over the 3.8 billion years since.
the heat from the earth would not have been much bigger than it is now.
The Earth was COMPLETELY MOLTEN at its inception (when the Moon was formed.) It is far from completely molten today; it's been gradually cooling.