Earth Didn't Freeze Over - Why?

"Clouds May Hold Key to Why Early Earth Didn't Freeze Over"
Space.com (March 31, 2010)

"A paradox about the climate of the early Earth that has been plaguing scientists for nearly 50 years may have a new solution.

"The so-called 'young' sun paradox — first proposed by Carl Sagan and his colleague George Mullen in 1972 — refers to the fact that the Earth had liquid oceans for the first half of its more than 4-billion-year existence despite the fact that the sun was likely only 70 percent as bright in its youth as it is now.

"A lower solar luminosity should have left Earth's oceans frozen over, but there is ample evidence in the Earth's geological record that there was liquid water — and life — on the planet at the time.

"Over the past few decades, scientists have proposed several possible mechanisms that may have kept the Earth toasty enough to keep water from freezing during our planet's early history – a period of time called the Archaean. But just when scientists think they have the paradox solved, other researchers come up with alternate explanations or reasons why a previous proposal doesn't work...."

This idea may catch on - particularly since it involves greenhouse gasses that (all the 'right' people assume) are what's driving Global Warming: and that its humanity's fault. And maybe Earth's atmosphere trapped heat more effectively in the past than it does now because it had more carbon dioxide than it does now. Almost a third of Earth's atmosphere might have been carbon dioxide in 'the good old days.'

Or, not.

The article discusses that, and albedo - how much energy (specifically, light) gets bounced right back into space.

Various scientists have pretty good ideas to explain what happened. Several of them: some mutually contradictory. The only thing that's really certain is that Earth's oceans were liquid for a really, really long time. Aside from geological evidence, there's us: we're here, and that wouldn't be too likely if this planet's water had been frozen solid for much of its history.

None of this 'proves' that science is wrong. Collecting data, analyzing it, and working out mathematical models to explain the observations is how science works. I've written about this before. ("A Patron Saint of - Scientists?!" (October 25, 2009), "Faith and Reason, Religion and Science" (March 20, 2009), A Catholic Citizen in America, for starters)

And I'm not surprised that Earth hasn't always been just the way it has been for the last few centuries.

Related posts:

• "'Snowball Earth,' Evolution, and Really Old Rocks"
  (March 16, 2010)
• "Global Warming: on Pluto. And Mars"
  (December 14, 2009)
• "Global Warming and Lost Documentation - Or, Change Happens: Deal With It"
  (December 1, 2009)
• " 'Little Regularities' - A Thought for the Day"
  (September 23, 2009)
• "The Unchanging Sun and Earth's Climate"
  (August 28, 2009)

More:

• "Change, American Culture, Trilobites, Humanity's History, and the Big Picture "

An overview of the last 4,500,000,000 or so years on Earth:

• "Hadean time: 4.5 to 3.8 billion years ago"
• "Introduction to the Archaean 3.8 to 2.5 billion years ago"
• "Introduction to the Proterozoic Era 2.5 billion to 543 million years ago"
  • "Introduction to the Vendian Period 650 to 543 Million Years Ago"
• "The Paleozoic Era 543 to 248 Million Years Ago"
  • "The Cambrian Period 543 to 490 Million Years Ago"
    • "The Tommotian Age 530 Million Years Ago"
  • "The Ordovician 490 to 443 Million Years Ago"
  • "The Silurian 443 to 417 Million Years Ago"
  • "The Devonian 417 to 354 Million Years Ago"
  • "The Carboniferous 354 to 290 Million Years Ago"
  • "The Permian 290 to 248 Million Years Ago"
• "Introduction to the Mesozoic Era 248 to 65 Million Years Ago"
  • "The Triassic Period 248 to 206 Million Years Ago"
  • "The Jurassic Period 206 to 144 Million Years Ago"
  • "The Cretaceous Period 144 to 65 Million Years Ago"
• "Introduction to the Cenozoic 65 Million Years to the Present"
  • Tertiary (65 to 1.8 mya)
    • "The Paleocene Epoch 65 to 54.8 mya"
    • "The Eocene Epoch 54.8 to 33.7 mya"
    • "The Oligocene Epoch 33.7 to 23.8 mya"
    • "The Miocene Epoch 23.8 to 5.3 mya"
    • "The Pliocene Epoch 5.3 to 1.8 mya"
  • Quaternary (1.8 mya to today)
    • "The Pleistocene 1.8 million to ~10,000 years ago"
    • "The Holocene The last ~10,000 years"
• News Time: The Last Few Days
  (Sources: University of California Museum of Paleontology and CNN)

(from "The Ice is Falling! Runaway Melt Mode! And You Should See What's Happening to Minnesota Trees!" (September 23, 2009)