Nature Ice Age , Sahara desert, Earth's wobble and the Gulf Stream

Now Gavin Schmidt of NASA mentions that 8,000 years ago when the Sahara turned into a desert the tilt was 24.1 degrees and that today’s tilt is 23.5 degrees. 24.1-23.5 = 0.6 degree. The Milankovitch cycle for the axial tilt is 41,000 years from 21.5 degrees -> 24.5 to 21.5 degrees which is 6 degrees. Each degree takes 41,000/6 = 6833 years to complete. Then from 24.1 degrees to 23.5 degrees = 0.6 degree which is 0.6*6833 = 4,099 years. So it has to be 24.1 degrees over the hump 24.5 degrees in the cycle when the Sahara turned into a desert. 24.1 degrees -> 24.5 ->24.1 to 23.5 degrees i.e. 1.6 degrees. 1.6 * 6833 = 10,932 years. But I ignored the precession which gives the cycle that frilly appearance. Anyway it is approximate.
The LGM (Last Glacial Maximum) was 20,000 to 19,000 years ago and the Younger Dryas was 12,500 to 11,500 years ago. So we can try to envision which part of the cycle the LGM was in.
Today’s axial tilt is 23.5 degrees so 20,000 years ago is nearly equal to half of the axial cycle. As shown above the 8,000 years for drying of the Sahara was just over the hump 24.5 degrees so it was from 21.5 degrees to 24.5 degrees when LGM and the Younger Dryas (drying period) occurred as well of the desertification of the Sahara. Note the tilt is measured from the vertical of the elliptic plane so increasing the tilt means going down from the North pole. So the cooling period was shrinking of the tropical region as the sun oscillated from 21.5 degrees north (Tropic of Cancer) to 21.5 degrees south (Tropic of Capricorn).
Now we are at 23.5 degrees and going to 21.5 degrees which is increasing the tropical zone as the Tropics of Cancer and Capricorn are moving outwards so there is a warming of the earth till the sun reaches 21.5 degrees and starts increasing in axial tilt from 21.5 degrees to 24.5 degrees which would be the cooling period. 23.5 – 21.5 = 2 degrees which translate to 6833*2 = 13,766 years. So the cooling starts approximately 14,000 years from now and hopefully not another Ice Age.
Now this calculation I did only shows the energy input to earth from the sun. The eccentricity shows the path the earth takes around the sun oscillating from near circle to an ellipse. This shows the sun’s radiation would vary as the earth distance from the sun varies.
The axial tilt shows where the sun’s path is along the earth’s surface in effect dictates the tropical region's size and the precession is the North pole going in circles every 23,000 per cycle which gives a zig-zag pattern to the path of the sun as it oscillates between the Tropics.
The Milankovitch cycles only shows the energy input of the sun to the earth so it is not a complete view of the Ice Ages. The distribution of energy in the form of ocean and wind currents which change with the configuration of the continents which are not constant due to tectonic plate mechanics. Vegetation affects distribution as it moderates temperature over land surfaces as it absorbs sunlight and animals start living there so it is warmed by the animals at night. Then there is the heat loss from cloud and snow cover and greenhouse gases (which slows the heat loss). These would be difficult to include in the equations but must be adjusted for each period in earth’s history.

Eccentricity
The first of the three Milankovitch Cycles is the Earth's eccentricity. Eccentricity is, simply, the shape of the Earth's orbit around the Sun. This constantly fluctuating, orbital shape ranges between more and less elliptical (0 to 5% ellipticity) on a cycle of about 100,000 years.These oscillations, from more elliptic to less elliptic, are of prime importance to glaciation in that it alters the distance from the Earth to the Sun, thus changing the distance the Sun's short wave radiation must travel to reach Earth, subsequently reducing or increasing the amount of radiation received at the Earth's surface in different seasons.

clip_image001.jpg


Today a difference of only about 3 percent occurs between aphelion (farthest point) and perihelion (closest point). This 3 percent difference in distance means that Earth experiences a 6 percent increase in received solar energy in January than in July. This 6 percent range of variability is not always the case, however.When the Earth's orbit is most elliptical the amount of solar energy received at the perihelion would be in the range of 20 to 30 percent more than at aphelion. Most certainly these continually altering amounts of received solar energy around the globe result in prominent changes in the Earth's climate and glacial regimes. At present the orbital eccentricity is nearly at the minimum of its cycle.


Axial Tilt
Axial tilt, the second of the three Milankovitch Cycles, is the inclination of the Earth's axis in relation to its plane of orbit around the Sun. Oscillations in the degree of Earth's axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees.

clip_image002.jpg


Today the Earth's axial tilt is about 23.5 degrees, which largely accounts for our seasons. Because of the periodic variations of this angle the severity of the Earth's seasons changes. With less axial tilt the Sun's solar radiation is more evenly distributed between winter and summer. However, less tilt also increases the difference in radiation receipts between the equatorial and polar regions.
One hypothesis for Earth's reaction to a smaller degree of axial tilt is that it would promote the growth of ice sheets. This response would be due to a warmer winter, in which warmer air would be able to hold more moisture, and subsequently produce a greater amount of snowfall. In addition, summer temperatures would be cooler, resulting in less melting of the winter's accumulation. At present, axial tilt is in the middle of its range.


Precession
The third and final of the Milankovitch Cycles is Earth's precession. Precession is the Earth's slow wobble as it spins on axis. This wobbling of the Earth on its axis can be likened to a top running down, and beginning to wobble back and forth on its axis. The precession of Earth wobbles from pointing at Polaris (North Star) to pointing at the star Vega. When this shift to the axis pointing at Vega occurs, Vega would then be considered the North Star. This top-like wobble, or precession, has a periodicity of 23,000 years.

clip_image003.jpg


Due to this wobble a climatically significant alteration must take place. When the axis is tilted towards Vega the positions of the Northern Hemisphere winter and summer solstices will coincide with the aphelion and perihelion, respectively.This means that the Northern Hemisphere will experience winter when the Earthis furthest from the Sun and summer when the Earth is closest to the Sun. This coincidence will result in greater seasonal contrasts. At present, theEarth is at perihelion very close to the winter solstice.

Eccentricity
The first of the three Milankovitch Cycles is the Earth's eccentricity. Eccentricity is, simply, the shape of the Earth's orbit around the Sun. This constantly fluctuating, orbital shape ranges between more and less elliptical (0 to 5% ellipticity) on a cycle of about 100,000 years. These oscillations, from more elliptic to less elliptic, are of prime importance to glaciation in that it alters the distance from the Earth to the Sun, thus changing the distance the Sun's short wave radiation must travel to reach Earth, subsequently reducing or increasing the amount of radiation received at the Earth's surface in different seasons.​
eccentric.JPG
Today a difference of only about 3 percent occurs between aphelion (farthest point) and perihelion (closest point). This 3 percent difference in distance means that Earth experiences a 6 percent increase in received solar energy in January than in July. This 6 percent range of variability is not always the case, however. When the Earth's orbit is most elliptical the amount of solar energy received at the perihelion would be in the range of 20 to 30 percent more than at aphelion. Most certainly these continually altering amounts of received solar energy around the globe result in prominent changes in the Earth's climate and glacial regimes. At present the orbital eccentricity is nearly at the minimum of its cycle.​

Axial Tilt
Axial tilt, the second of the three Milankovitch Cycles, is the inclination of the Earth's axis in relation to its plane of orbit around the Sun. Oscillations in the degree of Earth's axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees.​
axial.JPG
Today the Earth's axial tilt is about 23.5 degrees, which largely accounts for our seasons. Because of the periodic variations of this angle the severity of the Earth's seasons changes. With less axial tilt the Sun's solar radiation is more evenly distributed between winter and summer. However, less tilt also increases the difference in radiation receipts between the equatorial and polar regions.​
One hypothesis for Earth's reaction to a smaller degree of axial tilt is that it would promote the growth of ice sheets. This response would be due to a warmer winter, in which warmer air would be able to hold more moisture, and subsequently produce a greater amount of snowfall. In addition, summer temperatures would be cooler, resulting in less melting of the winter's accumulation. At present, axial tilt is in the middle of its range.​

Precession
The third and final of the Milankovitch Cycles is Earth's precession. Precession is the Earth's slow wobble as it spins on axis. This wobbling of the Earth on its axis can be likened to a top running down, and beginning to wobble back and forth on its axis. The precession of Earth wobbles from pointing at Polaris (North Star) to pointing at the star Vega. When this shift to the axis pointing at Vega occurs, Vega would then be considered the North Star. This top-like wobble, or precession, has a periodicity of 23,000 years.​
precess.JPG
Due to this wobble a climatically significant alteration must take place. When the axis is tilted towards Vega the positions of the Northern Hemisphere winter and summer solstices will coincide with the aphelion and perihelion, respectively. This means that the Northern Hemisphere will experience winter when the Earth is furthest from the Sun and summer when the Earth is closest to the Sun. This coincidence will result in greater seasonal contrasts. At present, the Earth is at perihelion very close to the winter solstice.​

http://www.indiana.edu/~geol105/images/gaia_chapter_4/milankovitch.htm
 
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I decided to revise my analysis of the Ice Age here instead of editing the earlier posting which had some errors. I ought it would better to show my writing "with warts and all" as the saying goes as I make modifications to my thoughts. Here is my update

Now Gavin Schmidt of NASA mentions that 8,000 years ago when the Sahara turned into a desert the tilt was 24.1° and that today’s tilt is 23.5°. 24.1° - 23.5° = 0.6°. The Milankovitch cycle for the axial tilt is 41,000 years from 21.5° -> 24.5° to 21.5° degrees which is 6°. Each degree takes 41,000/6 =6,833 years. Then 24.1° to 23.5° = 0.6 degree which is 0.6 * 6833 = 4099 years. So it has to be 24.1° over the hump 24.5° in the cycle when the Sahara turned into a desert. 24.1° -> 24.5° ->24.1° to 23.5° i.e. 1.6 degrees. 1.6 * 6833 =10,932 years. But I ignored the precession which gives the cycle that frilly appearance. Anyway it is approximate.

The LGM (Last Glacial Maximum) was 20,000 to 19,000 years ago and the Younger Dryas was 12,500 to 11,500 years ago. So we can try to envision which part of the cycle the LGM was in.

Today’s axial tilt is 23.5° so 20,000 years ago is nearly equal to half of the axial cycle. As shown above the 8,000 years for drying of the Sahara was just over the hump 24.5° so it was slope from 21.5° to 24.5° when LGM and the Younger Dryas (drying period) occurred as well of the desertification of the Sahara. Note the axial tilt is from the vertical of the elliptic plane so increasing the tilt means the North Pole is approaching the equator.

The axial tilt today is 23.5° and heading towards 21.5°. The less tilt the closer the Tropics are to the equator. The tropical region is therefore shrinking and so it is cooling. The cooling occurs from the shrinking of the tropical region till the sun oscillates finally from 21.5° north (Tropic of Cancer) to 21.5° south (Tropic of Capricorn).

Note: One needs a globe to help visualize this axial tilt and the Tropics which mark the maximum angle from the equator during summer and winter. I got confused and had to look at my small globe many times.

Now we are at 23.5° and going towards 21.5° which is decreasing the tropical zone. As the tropics of Cancer and Capricorn are moving inwards there is a cooling of the earth till the sun reaches 21.5° and then starts increasing in axial tilt which would begin the heating period. 23.5° – 21.5° = 2° which translate to 6833 * 2 = 13,766 years. We are in the middle of the Ice Age so the Ice Age ends approximately 14,000 years from now and hopefully ending the Ice Age.

The coldest time would be when the sun moves from 22.5° -> 21.5° back to 22.5° that period of 2 degrees the tropical region is smallest for 2 * 6,833 or 13,666 years. The hottest would be at 23.5° -> 24.5° back to 23.5° for another 13,666 years with the tropical region at its widest. The Ice Ages could extend through both periods as snow and ice cover would deflect most of the sunshine.

The various ways out of the Ice Age would be to absorb the sunlight with a huge volcanic eruption which could happen with thick ice pressing bending the rocks and soil on a volcano as it builds up pressure internally. The combined pressure would prematurely cause an eruption. Greenhouse gases could be released. The ash would spread over the snow and darken the surface as well as melt some of the snow. The caldera of the volcano could alter wind patterns.

Volcanic deposits could create barriers and divert warm equatorial ocean currents up north e.g. the Gulf of Mexico was closed off and the Gulf Stream was created 3 million years ago.

The drying of the Sahara into a full blown desert would also help by heating the atmosphere during the day and inducing hurricanes which would spread warm over a large area. Of course, the tropical region was free from snow and ice most of the time through the Ice Ages.

The Sahara was dried (24.1°) up during the warmest period from 23.5° -> back to 23.5° (the present period) lasting 13,666 years. We are at the end of the warming period with widest tropical region and will start to shrink. There is a lag as it takes time to cool so the earth is warming plus the human activity may also be adding heat to the earth.

Now this calculation I did only shows the energy input to earth from the sun. The eccentricity shows the path takes around the sun oscillating from near circle to an ellipse. This shows the sun’s radiation would vary as the earth distance from the sun varies.

The axial tilt shows where the sun’s path is along the earth’s surface in effect the tropical region and the precession is the North Pole going in circles every 23,000 per cycle which gives a zigzag pattern to the path of the sun as it oscillates between the Tropics.

The Milankovitch cycles only show the energy input of the sun to the earth so it not a complete view of the Ice Ages. The distribution, or circulation, of energy in the form of ocean and wind current change with the configuration of the continents which are not constant due to tectonic plate mechanics.

Vegetation affects distribution as it moderate temperature over land surfaces as it absorbs sunlight and animals start living there so it is warmed by the animals at night. Then there is the heat loss from cloud and snow cover and greenhouse gases (which slow the heat loss). These would be difficult to include in the equation but must be adjusted for each period in earth’s history.

[/QUOTE]
 
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Eccentricity
The first of the three Milankovitch Cycles is the Earth's eccentricity. Eccentricity is, simply, the shape of the Earth's orbit around the Sun. This constantly fluctuating, orbital shape ranges between more and less elliptical (0 to 5% ellipticity) on a cycle of about 100,000 years.These oscillations, from more elliptic to less elliptic, are of prime importance to glaciation in that it alters the distance from the Earth to the Sun, thus changing the distance the Sun's short wave radiation must travel to reach Earth, subsequently reducing or increasing the amount of radiation received at the Earth's surface in different seasons.
2Q==

Today a difference of only about 3 percent occurs between aphelion (farthest point) and perihelion (closest point). This 3 percent difference in distance means that Earth experiences a 6 percent increase in received solar energy in January than in July. This 6 percent range of variability is not always the case, however. When the Earth's orbit is most elliptical the amount of solar energy received at the perihelion would be in the range of 20 to 30 percent more than at aphelion. Most certainly these continually altering amounts of received solar energy around the globe result in prominent changes in the Earth's climate and glacial regimes. At present the orbital eccentricity is nearly at the minimum of its cycle.
 
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Axial Tilt
Axial tilt, the second of the three Milankovitch Cycles, is the inclination of the Earth's axis in relation to its plane of orbit around the Sun. Oscillations in the degree of Earth's axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees.
Z

Today the Earth's axial tilt is about 23.5 degrees, which largely accounts for our seasons. Because of the periodic variations of this angle the severity of the Earth's seasons changes. With less axial tilt the Sun's solar radiation is more evenly distributed between winter and summer. However, less tilt also increases the difference in radiation receipts between the equatorial and polar regions.
One hypothesis for Earth's reaction to a smaller degree of axial tilt is that it would promote the growth of ice sheets. This response would be due to a warmer winter, in which warmer air would be able to hold more moisture, and subsequently produce a greater amount of snowfall. In addition, summer temperatures would be cooler, resulting in less melting of the winter's accumulation. At present, axial tilt is in the middle of its range.

 
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Precession
The third and final of the Milankovitch Cycles is Earth's precession. Precession is the Earth's slow wobble as it spins on axis. This wobbling of the Earth on its axis can be likened to a top running down, and beginning to wobble back and forth on its axis. The precession of Earth wobbles from pointing at Polaris (North Star)to pointing at the star Vega. When this shift to the axis pointing at Vega occurs, Vega would then be considered the North Star. This top-like wobble, or precession, has a periodicity of 23,000 years.
2Q==

Due to this wobble a climatically significant alteration must take place. When the axis is tilted towards Vega the positions of the Northern Hemisphere winter and summer solstices will coincide with the aphelion and perihelion, respectively. This means that the Northern Hemisphere will experience winter when the Earth is furthest from the Sun and summer when the Earth is closest to the Sun. This coincidence will result in greater seasonal contrasts. At present, the Earth is at perihelion very close to the winter solstice.

http://theresilientearth.com/?q=content/sun-cycles-heat-ice-age-interglacials

http://theresilientearth.com/files/images/past_10_interglacials-yin_natgeo2010.png

http://www.indiana.edu/~geol105/images/gaia_chapter_4/milankovitch.htm

<font color="#000000"><span style="font-family: Times New Roman"><a href="http://www.indiana.edu/~geol105/images/gaia_chapter_4/milankovitch.htm" target="_blank" rel="nofollow">

 
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While we are at Sahara desert I think the Egyptians should think about creating an inland lake by Libyan desert depression by opening a channel to the Mediterranean Sea. There are depressions below sea level in various parts of the world vis-a-vis:

Egypt - Libyan desert Depression
China - Taklamakan desert depression
Australia -
Israel - Dead Sea
USA - Death Valley
Eritria -
Kazakhstan - near Caspian Sea
 
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Z

Z


http://theresilientearth.com/?q=content/confirmed-orbital-cycles-control-ice-ages
Causes

The prevailing theory is that the Younger Dryas was caused by significant reduction or shutdown of the North Atlantic "Conveyor", which circulates warm tropical waters northward, in response to a sudden influx of fresh water from Lake Agassiz and deglaciation in North America. Geological evidence for such an event is thus far lacking.[15] The global climate would then have become locked into the new state until freezing removed the fresh water "lid" from the north Atlantic Ocean.An alternative theory suggests instead that the jet stream shifted northward in response to the changing topographic forcing of the melting North American ice sheet, bringing more rain to the North Atlantic which freshened the ocean surface enough to slow the thermohaline circulation.[16] There is also some evidence that a solar flare may have been responsible for the mega faunal extinction, though it cannot explain the apparent variability in the extinction across all continents.[17]

<span style="font-family: Times New Roman"><sup><a href="file:///E:/downloads/Firefox/ice%20age/Younger%20Dryas%20-%20Wikipedia,%20the%20free%20encyclopedia.htm#cite _note-17" target="_blank" rel="nofollow"><font size="2"><font color="#0000ff">


 
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There is evidence that some previous glacial terminations had post glacial cooling periods similar to the Younger Dryas.[18]
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9k=


<span style="font-family: Times New Roman">
 
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9k=


9k=


Shown above is a comparison of the benthic δ18O record through T-I (orange crosses;plotted on the upper timescale) and T-II (black crosses; plotted on the lower timescale), showing similarities in the duration of both terminations. Southern Hemisphere summer insolation at 65°S (blue) and obliquity curves (red) for T-I (dashed lines) and T-II (solid lines), and obliquity. The gray vertical bar marks the commencement points for both terminations,revealing an age difference of ~123,000 years, which is equivalent to three obliquity cycles of ~41,000 years each. As the author's put it: “Our record reveals that Terminations I and II are separated by three obliquity cycles and that they started at near-identical obliquity phases.”
 
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Z


Z


The images don't show. Too bad

<span style="font-family: Times New Roman">
 
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Luckily the orbit of the earth is a near circle. When the orbit is an ellipse the difference in sun's radiation can be from 20 or 30% i.e. the difference when the earth is closer to the sun (perihelion) and when it farther away (aphelion)

http://www.skepticalscience.com/Milankovitch.html.

It is snow cover that is the main culprit for the Ice Age as it reflect the sunlight away from the earth. Stagnant snow and accumulated snow results in ice and the ice can block the flow of ocean currents thus preventing warm currents that give warmth to continents by way of warm ocean breezes. The Ice Age is mostly a northern hemispheric phenomenon as most land masses are in the north. Russia and Canada are the two largest countries in the world and they are near the North Pole.

How the snow/ice affects CO2? The snow/ice buries the trees thus killing them and the animals living there. Trees at night respire like all living creatures by taking in oxygen and breathing out CO2. Carbon is locked in thus disrupting the carbon cycle.

I guess we must take stock of the situation and prepare for the onset of the Ice Age. We must take advantage of the global warming and do the necessary work to install infrastructure to combat snow buildup. Maybe power stations could be installed further up north. Black soot or dust can be piled up to be spread over the snow after snowfalls. Plant trees on barren land and burn fossil fuels. Have tracked snow plows to gather snow in piles to reduce surface area the snow may take. Place dynamite where ice bridges may form to block warm ocean currents that flow north, etc.
 
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Ice Age death trap

 
A real COLD War should be declared not against nations but against the cold to fight the Ice Age. The northern countries need to co-operate or they could become refugees to the south. Russia, Canada, Scandinavian countries, Poland, Lithuania, Latvia, Estonia, Belarus, Ukraine, Northern Germany, UK would be affected and Korea and Northern China and the Central Asia like Kyrgyzstan, Uzbekistan, Kazakhstan, Turkmenistan, Tajikistan would also be affected.
 
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Death of the Ice Man

 
A real COLD War should be declared not against nations but against the cold to fight the Ice Age. The northern countries need to co-operate or they could become refugees to the south. Russia, Canada, Scandinavian countries, Poland, Lithuania, Latvia, Estonia, Belarus, Ukraine, Northern Germany, Uk would be affected and Korea and Northern China and the Central Asia like Kyrgyzstan, Uzbekistan, Kazakhstan, Turkmenistan, Tajikistan would also be affected.

it's good to hear another opinion for once
i don't think there will come a new ice age because of global warming

but i'm sick of people discussing global warming without knowing anything about climate
they should study ice age first before talking
 
I am not in either camp but like to look at the issue objectively.


I forgot to take into account of human civilization. Since the great ice melt there has been many large cities that in the north e.g. Moscow, Toronto, Montreal, Helsinki, Stockholm, Copenhagen, Hamburg, Berlin, London, New York, Chicago, etc. These cities produce a lot of heat in winter nights. Then the millions of cars, trucks, ships and airplanes produce heat and CO2 which help insulate earth so up to 22 degrees mark where the Tropic of Cancer 3,416 years from now is the neutral point, there will not likely be an Ice Age. Of course, it depends on the energy situation. Will we run out of oil? We could switch to nuclear energy.

After 22 degrees mark the tropical region will shrink as the Tropic of Cancer heads towards 21.5 degrees. However, the earth's orbit is nearly circular so the energy input is the same except it is concentrated in the tropical region. But then the northern hemisphere will receive less sunshine and this is where little Ice Ages could occur in the northern regions. Little Ice Ages could be nasty as shown by the video above. It won't be until the earth's orbit turn to an elliptical path when the REAL Ice Age could occur with sun's radiation from the perihelion point (nearest to the sun) and the aphelion (farthest point from the sun) could differ by 20 to 30 %. The period in which this change is 100,000 years long enough time for humans if they survive to devise means to offset the Ice Age.

http://en.wikipedia.org/wiki/Earth's_orbit

http://en.wikipedia.org/wiki/Milankovitch_cycles

http://en.wikipedia.org/wiki/Milankovitch_cycles

http://www.sciencecourseware.org/eec/globalwarming/tutorials/milankovitch/
 
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I have been thinking. With the earth now entering the cooling cycle the Arctic Ocean may not be ice-free in the foreseeable future. Energy from human activity cannot match reduction of sun's radiation as it starts going south. It might have to be in the next warming cycle i.e. 23.5 degrees -> 22.5 -> to 21.5 degrees (2 degrees = 13,666 year) back to 22.5 to 23.5 degrees (another 2 degrees = 13,666 years) or 27,332 years, provided we can keep ice from forming during this period.
 
I have been thinking. With the earth now entering the cooling cycle the Arctic Ocean may not be ice-free in the foreseeable future. Energy from human activity cannot match reduction of sun's radiation as it starts going south. It might have to be in the next warming cycle i.e. 23.5 degrees -> 22.5 -> to 21.5 degrees (2 degrees = 13,666 year) back to 22.5 to 23.5 degrees (another 2 degrees = 13,666 years) or 27,332 years, provided we can keep ice from forming during this period.
That's why releasing CO2 to counteract Ice Age is a good thing.
 

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