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The_Absolute
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How long ago was the last ice age? Does an ice age pose any threats to species on Earth? If there were a 2nd ice age, would humanity survive it?
Depends on the geologic definition. Most put it at 11,400 years BP. Every estimate I have seen is falls into the 10,000 to 14,000 years BP range. Some would argue that we are in an ice age that began millions of years ago, and cycles between glacial and interglacial epochs.The_Absolute said:How long ago was the last ice age?
Does an ice age pose any threats to species on Earth?
If there were a 2nd ice age, would humanity survive it?
We are currently in the interglacial period of an Ice Epoch. The planet has cooled to the point it is starting to oscillate between extreme cold (glacial period) and cold (interglacial period).The_Absolute said:How long ago was the last ice age? Does an ice age pose any threats to species on Earth? If there were a 2nd ice age, would humanity survive it?
[1] For most of the Northern Hemisphere Ice Ages, from approx. 3.0 to 0.8 m.y., global ice volume varied predominantly at the 41,000 year period of Earth’s orbital obliquity. However, summer (or summer caloric half year) insolation at high latitudes, which is widely believed to be the major influence on high-latitude climate and ice volume, is dominated by the 23,000 year precessional period. Thus the geologic record poses a challenge to our understanding of climate dynamics.
Human beings may have had a brush with extinction 70,000 years ago, an extensive genetic study suggests. The human population at that time was reduced to small isolated groups in Africa, apparently because of drought, according to an analysis released Thursday. The report notes that a separate study by researchers at Stanford University estimated the number of early humans may have shrunk as low as 2,000 before numbers began to expand again in the early Stone Age.
Saul said:As noted above humans where near extinction 70 kyr ago due to droughts that lasted thousands of years. At that time the total human population on the planet was reduced to around 2000 which is close to the limit to maintain genetic diversity.
False. The planet has been cooling for the past 4.5 billion years as radioactive elements have become increasingly scarce due to short half-life isotopes (i.e. H3) and by various tectonic processes that work to remove heat from the Earth's core.Saul said:The planet has been cooling for the last 10 million years.
False. The first known glacial deposits and ice sheets are in Africa approximately where the Sahara desert is now because it used to be at the south pole.Saul said:As the planet cooled, the first ice sheets that formed where in the Antarctic. As the planet cooled further ice sheets started to form in the Northern Hemisphere.
l_ron_hubbard said:False. The planet has been cooling for the past 4.5 billion years as radioactive elements have become increasingly scarce due to short half-life isotopes (i.e. H3) and by various tectonic processes that work to remove heat from the Earth's core.
l_ron_hubbard said:Sylas, that is just wrong. Take the following image for example:
Surface radiation accounts for the plurality of energy in our atmosphere and is directly related to subsurface thermal processes. If it wasn't for radiative decay of elements in the mantle and core (and perhaps i should have included the mantle in my previous statement) this would be a barren planet without any mountain building as we know it. This heat flux from the Earth's interior is actually the mechanism that broke down the "snowball earth" which lead to the explosion of life in the Permian.
sylas said:Energy from inside the Earth does not figure in that diagram anywhere. All the surface radiation is accounted for by the energy coming in from the Sun. Just add up the numbers.
These geologic processes you elude to are constrained primarily by their thermal state, so it is therefore inaccurate to claim geothermal heat fluxes have "nothing to do" with carbon fluxes.You are awfully mixed up there. The mountain building is true enough, because this comes from plate tectonics, which is driven from inside the Earth. But you are incorrect about snowball earth. Melting of snowball Earth has nothing to do with geothermal heat fluxes. In the snowball Earth model, the melting of the snowball occurs from a build up of carbon dioxide, which comes from geological processes. But what counts from the interior is the carbon, that traps heat from the Sun. The actual heat that melts snowball Earth is surface heat driven by the Sun. Geothermal heat has no role at all in melting snowball earth.
The geothermal energy flux works out to a bit less than 0.05 W/m2. It is far too small to show up in the diagram you are using, which is all about climate and surface temperature -- all of which is related to how energy from the Sun is distributed.
Cheers -- sylas
l_ron_hubbard said:Perhaps I am missing something, but the incoming radiation is 341, 161 making its way into the earth, and the surface radiation is 356. That gives you a 195 W/m2 gap. When considering the thermal energy regularly released in volcanic activity, faulting, and other processes it would be hard to imagine that not playing a role in climate. There is an ongoing debate , however, among geomorphologists about climate forcing tectonics or tectonics forcing climate.
These geologic processes you elude to are constrained primarily by their thermal state, so it is therefore inaccurate to claim geothermal heat fluxes have "nothing to do" with carbon fluxes.
Where did you get that number from?
l_ron_hubbard said:That heat flow sounds more reasonable to me. I should know more about this since I am going to defend my Masters in Thermal Geophysics later this spring, but I must admit I know little about how that translates into climate processes... perhaps another of my short comings considering i attend the College of Oceanic and Atmospheric Sciences.
As far as my comment to geomorphology, see the following paper:
Landscape response to tectonic forcing: Digital elevation model analysis of stream profiles in the Mendocino triple junction region, northern California
Noah P. Snyder et. al.
and
Whipple 1999, Journal of Geophysical Research.
There is a more authoritative one by Molnar and England, who lead this field of science, but I can't remember what it is right now. I thought the idea of climate forcing tectonics was absurd when I first heard it in my geomorphology class last fall but it is surprisingly difficult to resolve the issue.
Saul said:As noted above humans where near extinction 70 kyr ago due to droughts that lasted thousands of years. At that time the total human population on the planet was reduced to around 2000 which is close to the limit to maintain genetic diversity.
An Ice Age is a period of time where the Earth experiences a significant drop in temperature, resulting in the expansion of polar ice sheets and glaciers. This can last for thousands of years.
Currently, the Earth is not showing any signs of entering a Second Ice Age. However, it is always a possibility as the Earth's climate is constantly changing.
The main threats to humanity during a Second Ice Age include food and water shortages, extreme weather events, and the spread of diseases due to crowded living conditions and lack of resources.
Unfortunately, it is difficult to predict when a Second Ice Age may occur. However, scientists are constantly monitoring changes in the Earth's climate and can provide warnings if significant changes are detected.
To increase our chances of survival during a Second Ice Age, we can take measures such as building shelters, stockpiling food and water, and developing technology to adapt to the harsh conditions. It is also important to work towards reducing our carbon footprint to prevent further changes in the Earth's climate.