|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Interstellar dust - ice ages?
I am a retired meteorologist - just an interest in astronomy. The last
ice age ended about 20k years ago. Nobody really knows why ice ages happen but I have often wondered about interstellar dust. Seems reasonable to me that as the solar system rotates around the galaxy it may encounter dust clouds which would reduce solar radiation reaching the Earth and thus trigger ice ages. There are some suggestions that the sun is a variable star. How would it be shown if this could just be due to interstellar dust? Would this dust actually be between the Earth and the Sun or would the solar 'wind' keep it away? |
#2
|
|||
|
|||
Interstellar dust - ice ages?
|
#3
|
|||
|
|||
Interstellar dust - ice ages?
"Pete L" wrote in message
... I am a retired meteorologist - just an interest in astronomy. The last ice age ended about 20k years ago. Nobody really knows why ice ages happen but I have often wondered about interstellar dust. Seems reasonable to me that as the solar system rotates around the galaxy it may encounter dust clouds which would reduce solar radiation reaching the Earth and thus trigger ice ages. There are some suggestions that the sun is a variable star. How would it be shown if this could just be due to interstellar dust? Would this dust actually be between the Earth and the Sun or would the solar 'wind' keep it away? The current ice age did not end 20 k years ago. With ice at both poles we are still in it! What did occur 20 ka was the last glacial maximum, and we are now in an interglacial. The previous interglacial (the Eemian) happened about 100 k years ago and lasted about 10 k years. The current interglacial (the Holocene) has lasted about 10 k years so far. The cause of glacials and interglacials is known. It is related to the Earth's orbit around the Sun by a mechanism known as Milankovitch cycles. These cycles have periods of roughly 21 k, 41 k and 100 k years. The overall cycle consists of a 80 k cooling, 10 k warming and 10 k interglacial. During the rapid warming CO2 concentration increases and it is believed that it acts as a positive feedback. The ice ages (the first of which goes back to 2,000 M years ago,) seems to have been be caused by episodic drawdowns of carbon dioxide from the atmosphere as life evolved in a world where the Sun has grown steadily stronger, but there is still doubt about the causes of each of those. Dust from volcanoes, when injected into the stratosphere, does cause cooling e.g. Tambora in 1815 caused 1816 to be the year without a summer, but interstellar dust would not be dense enough to have had such an effect. Cheers, Alastair. |
#4
|
|||
|
|||
Interstellar dust - ice ages?
On Dec 27, 10:50*pm, "Alastair McDonald"
wrote: "Pete L" wrote in message ... I am a retired meteorologist - just an interest in astronomy. The last ice age ended about 20k years ago. Nobody really knows why ice ages happen but I have often wondered about interstellar dust. Seems reasonable to me that as the solar system rotates around the galaxy it may encounter dust clouds which would reduce solar radiation reaching the Earth and thus trigger ice ages. There are some suggestions that the sun is a variable star. How would it be shown if this could just be due to interstellar dust? Would this dust actually be between the Earth and the Sun or would the solar 'wind' keep it away? The current ice age did not end 20 k years ago. With ice at both poles we are still in it! What did occur 20 ka was the last glacial maximum, and we are now in an interglacial. The previous interglacial (the Eemian) happened about 100 k years ago and lasted about 10 k years. The current interglacial (the Holocene) has lasted about 10 k years so far. The cause of glacials and interglacials is known. It is related to the Earth's orbit around the Sun by a mechanism known as Milankovitch cycles. These cycles have periods of roughly 21 k, 41 k and 100 k years. The overall cycle consists of a 80 k cooling, 10 k warming and 10 k interglacial. During the rapid warming CO2 concentration increases and it is believed that it acts as a positive feedback. The ice ages (the first of which goes back to 2,000 M years ago,) seems to have been be caused by episodic drawdowns of carbon dioxide from the atmosphere as life evolved in a world where the Sun has grown steadily stronger, but there is still doubt about the causes of each of those. Dust from volcanoes, when injected into the stratosphere, does cause cooling e.g. Tambora in 1815 caused 1816 to be the year without a summer, but interstellar dust would not be dense enough to have had such an effect. Cheers, Alastair. Yes, I know about Milankovitch - is it not a case that we are about (+/-) a few hundred years, to go into the next downturn? I've often wondered if man's input of CO2 is actually holding off the next Ice Age. Would be ironic really! |
#5
|
|||
|
|||
Interstellar dust - ice ages?
"Pete L" wrote in message ... Yes, I know about Milankovitch - is it not a case that we are about (+/-) a few hundred years, to go into the next downturn? I've often wondered if man's input of CO2 is actually holding off the next Ice Age. Would be ironic really! The two main theories about the next glacial a 1) Mankind has already prevented it with the introduction of farming. Crops do not drawdown the CO2 that forests do and so the widespread clearing of land for farming has kept the CO2 levels high. Moreover, the rice paddies produce methane which is an even more powerful greenhouse gas. Thus our influence on climate goes back thousands of years. [ http://en.wikipedia.org/wiki/William_Ruddiman ] 2) The ellipticity of the Earth is decreasing and so the next Milankovitch cooling will not happen for about 40 thousand years anyway. [ http://www.sciencemag.org/content/297/5585/1287 ] Recently, Berger & Loutre have proposed that the next glacial may have been banished forever. http://www.nature.com/news/2002/0208...s020819-9.html I am not sure that would be ironic. It will result in a sea level rise of over 60 m (200 feet) which will flood most farmland since it is mainly situated on coastal plains. A 6 metre sea level rise might be held back with flood defences but not 60 m. Cheers, Alastair. |
#6
|
|||
|
|||
Interstellar dust - ice ages?
On Dec 28, 3:04*pm, "Alastair McDonald"
wrote: "Pete L" wrote in message ... Yes, I know about Milankovitch - is it not a case that we are about (+/-) a few hundred years, to go into the next downturn? I've often wondered if man's input of CO2 is actually holding off the next Ice Age. Would be ironic really! The two main theories about the next glacial a 1) Mankind has already prevented it with the introduction of farming. Crops do not drawdown the CO2 that forests do and so the widespread clearing of land for farming has kept the CO2 levels high. Moreover, the rice paddies produce methane which is an even more powerful greenhouse gas. Thus our influence on climate goes back thousands of years. [http://en.wikipedia.org/wiki/William_Ruddiman] 2) The ellipticity of the Earth is decreasing and so the next Milankovitch cooling will not happen for about 40 thousand years anyway. [http://www.sciencemag.org/content/297/5585/1287] Recently, Berger & Loutre have proposed that the next glacial may have been banished forever.http://www.nature.com/news/2002/0208...20819-9..htmlI am not sure that would be ironic. It will result in a sea level rise of over 60 m (200 feet) which will flood most farmland since it is mainly situated on coastal plains. A 6 metre sea level rise might be held back with flood defences but not 60 m. Cheers, Alastair. Sorry guys,Milankovitch as an assertion is obsolete while precession as a long term axial trait is untenable also - this is a conclusion drawn from direct observation where the polar latitudes are carried around in a circle to the central Sun and act like a beacon for the orbital behavior of a planet - http://www.daviddarling.info/images/...gs_changes.jpg Axial precession goes from a long term axial trait to an orbital orbital trait and the degree of inclination is given a new role in assigning a planetary climate spectrum between polar (90 degree inclination) to equatorial (0 degree inclination). The old 'no tilt/no seasons' is replaced by a 21st century perspective which introduces a planetary climate spectrum with the Earth having a largely equatorial climate.Meteorology is a subset of astronomy and although it is possible to predict short term weather using known components of the atmosphere,land and sea,it is impossible to study climate proper outside astronomy. Milankovitch indeed ! - try understanding the cause for the annual Arctic sea ice fluctuations as the polar latitude is carried around in a circle to the central Sun about an ecliptic axis that runs coincident with the circle of illumination - http://www.msss.com/mars_images/moc/...mericas250.jpg |
#7
|
|||
|
|||
Interstellar dust - ice ages?
"Pete L" napisal w wiadomosci ... I am a retired meteorologist - just an interest in astronomy. The last ice age ended about 20k years ago. Nobody really knows why ice ages happen but I have often wondered about interstellar dust. Seems reasonable to me that as the solar system rotates around the galaxy it may encounter dust clouds Dust clouds also rotate. But in space are many travelers (comets). Direct colission with one of the US planets can produce the interplanetary dust. And which would reduce solar radiation reaching the Earth and thus trigger ice ages. There are some suggestions that the sun is a variable star. How would it be shown if this could just be due to interstellar dust? Would this dust actually be between the Earth and the Sun or would the solar 'wind' keep it away? The solar wind is "made of" the comets which fall down on the Sun. More comets, more solar wind and in the result the higher temperature on the Earth. Now the interplanetary dust is behind the Mars. S* |
#8
|
|||
|
|||
Interstellar dust - ice ages?
On 28/12/2012 15:04, Alastair McDonald wrote:
"Pete L" wrote in message ... Yes, I know about Milankovitch - is it not a case that we are about (+/-) a few hundred years, to go into the next downturn? I've often wondered if man's input of CO2 is actually holding off the next Ice Age. Would be ironic really! The two main theories about the next glacial a 1) Mankind has already prevented it with the introduction of farming. Crops do not drawdown the CO2 that forests do and so the widespread clearing of land for farming has kept the CO2 levels high. Moreover, the rice paddies produce methane which is an even more powerful greenhouse gas. Thus our influence on climate goes back thousands of years. [ http://en.wikipedia.org/wiki/William_Ruddiman ] 2) The ellipticity of the Earth is decreasing and so the next Milankovitch cooling will not happen for about 40 thousand years anyway. [ http://www.sciencemag.org/content/297/5585/1287 ] Recently, Berger & Loutre have proposed that the next glacial may have been banished forever. http://www.nature.com/news/2002/0208...s020819-9.html I am not sure that would be ironic. It will result in a sea level rise of over 60 m (200 feet) which will flood most farmland since it is mainly situated on coastal plains. A 6 metre sea level rise might be held back with flood defences but not 60 m. Cheers, Alastair. Thanks for a very interesting post; I will certainly follow those links. -- For every complex problem, there is a solution which is simple, neat, and wrong. H L Menken |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Could Adenine From Interstellar Dust Have Triggered Life On Earth? Elsewhere? | Double-A[_1_] | Misc | 0 | October 3rd 07 09:50 AM |
Interstellar Dust Bunnies in Taurus: Baby Steps toward New Planets?(Forwarded) | Andrew Yee | Astronomy Misc | 0 | January 10th 06 05:56 AM |
Ice Ages and interstellar hydrogen | Angelo Campanella | Misc | 21 | January 8th 05 06:13 AM |
Ice Ages and interstellar hydrogen | Angelo Campanella | UK Astronomy | 16 | January 8th 05 06:13 AM |
Interstellar Dust does it remind you of? | NGC 6826 | Amateur Astronomy | 2 | February 19th 04 04:35 PM |