Jan 1, 2023 05:42 PM
https://thedebrief.org/snowball-earth-wa...ly-frozen/
EXCERPTS: The standard solar model implies that the newly born Sun, 4.6 billion years ago, was a third fainter than it is today. Four billion years ago, the Sun was shining at three-quarters of its present-day luminosity. If Earth trapped the same fraction of sunlight 4 billion years ago as it does today, then its surface temperature would have been 20 degrees Kelvin colder.
The impact of reduced Solar irradiation on the Earth’s climate must have been larger though, as a result of the higher reflectivity of ice, further enhancing the cooling that occurred...
[...] Why was the surface of early Earth not fully frozen?
The simplest explanation is that Earth may have been warmed by an atmospheric blanket of greenhouse gases, such as carbon dioxide and methane, along with nitrogen and hydrogen. The warming could have been provided entirely by a higher carbon dioxide concentration, which is predicted to result from the geochemical cycle that transformed carbonate rocks back into silicate rocks through volcanic activity. Additionally, the faster rotation of the early Earth may have changed how the oceans circulated–and thus how they trapped heat.
Was Earth’s surface ever totally frozen throughout its history?
[...] Tentative geological evidence suggests that Earth may have been frozen over during the Cryogenian era that lasted from 720 to 635 million years ago. This epoch was characterized by two major global glaciations, labeled as Snowball Earth events: the Sturtian glaciation at 717-660 million years ago and the Marinoan glaciation at 645 -635 million years ago.
Although these Snowball Earth episodes are neither well-understood nor universally accepted, the textbook titled “Life in the Cosmos” that I co-authored with my former postdoc, Manasvi Lingam, suggests that they could have been important for the eventual development of animals for multiple reasons... (MORE - missing details)
EXCERPTS: The standard solar model implies that the newly born Sun, 4.6 billion years ago, was a third fainter than it is today. Four billion years ago, the Sun was shining at three-quarters of its present-day luminosity. If Earth trapped the same fraction of sunlight 4 billion years ago as it does today, then its surface temperature would have been 20 degrees Kelvin colder.
The impact of reduced Solar irradiation on the Earth’s climate must have been larger though, as a result of the higher reflectivity of ice, further enhancing the cooling that occurred...
[...] Why was the surface of early Earth not fully frozen?
The simplest explanation is that Earth may have been warmed by an atmospheric blanket of greenhouse gases, such as carbon dioxide and methane, along with nitrogen and hydrogen. The warming could have been provided entirely by a higher carbon dioxide concentration, which is predicted to result from the geochemical cycle that transformed carbonate rocks back into silicate rocks through volcanic activity. Additionally, the faster rotation of the early Earth may have changed how the oceans circulated–and thus how they trapped heat.
Was Earth’s surface ever totally frozen throughout its history?
[...] Tentative geological evidence suggests that Earth may have been frozen over during the Cryogenian era that lasted from 720 to 635 million years ago. This epoch was characterized by two major global glaciations, labeled as Snowball Earth events: the Sturtian glaciation at 717-660 million years ago and the Marinoan glaciation at 645 -635 million years ago.
Although these Snowball Earth episodes are neither well-understood nor universally accepted, the textbook titled “Life in the Cosmos” that I co-authored with my former postdoc, Manasvi Lingam, suggests that they could have been important for the eventual development of animals for multiple reasons... (MORE - missing details)