Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
Interstellar dust - ice ages?
4 views
Skip to first unread message
Pete L
Dec 27, 2012, 10:24:48 AM12/27/12
to
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?
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?
Sjouke Burry
Dec 27, 2012, 1:39:50 PM12/27/12
to
Pete L <peterla...@hotmail.com> wrote in news:f6180bc3-1790-485a-
ac0f-138...@z2g2000vbx.googlegroups.com:
That dust would be blown out of the inner solar system by
radiation pressure.
It would also be heated, and re-emit sunlight as infrared.
So not much cooling is to be expected.
A really thick cloud might heat earth atmosfere instead, by
colliding with it at ~50km/sec.
ac0f-138...@z2g2000vbx.googlegroups.com:
radiation pressure.
It would also be heated, and re-emit sunlight as infrared.
So not much cooling is to be expected.
A really thick cloud might heat earth atmosfere instead, by
colliding with it at ~50km/sec.
Alastair McDonald
Dec 27, 2012, 4:50:33 PM12/27/12
to
"Pete L" <peterla...@hotmail.com> wrote in message
news:f6180bc3-1790-485a...@z2g2000vbx.googlegroups.com...
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.
news:f6180bc3-1790-485a...@z2g2000vbx.googlegroups.com...
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.
Pete L
Dec 28, 2012, 4:30:50 AM12/28/12
to
On Dec 27, 10:50 pm, "Alastair McDonald"
<a...@abmcdonald.freeserve.co.uk> wrote:
> "Pete L" <peterlaving...@hotmail.com> 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!
<a...@abmcdonald.freeserve.co.uk> wrote:
> "Pete L" <peterlaving...@hotmail.com> wrote in message
(+/-) 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!
Alastair McDonald
Dec 28, 2012, 10:04:28 AM12/28/12
to
news:82580e57-7a1c-4ce3...@hf3g2000vbb.googlegroups.com...
> 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 are:
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/2002/020823/full/news020819-9.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.
> 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!
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/2002/020823/full/news020819-9.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.
oriel36
Dec 28, 2012, 12:04:42 PM12/28/12
to
On Dec 28, 3:04 pm, "Alastair McDonald"
<a...@abmcdonald.freeserve.co.uk> wrote:
> "Pete L" <peterlaving...@hotmail.com> wrote in message
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/Uranus_rings_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/2003/05/22/earth_americas250.jpg
<a...@abmcdonald.freeserve.co.uk> wrote:
> "Pete L" <peterlaving...@hotmail.com> wrote in message
>
> news:82580e57-7a1c-4ce3...@hf3g2000vbb.googlegroups.com...
>
> > 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 are:
>
> 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/2002/020823/full/news020819-9.htmlI am not sure
> news:82580e57-7a1c-4ce3...@hf3g2000vbb.googlegroups.com...
>
> > 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 are:
>
> 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
> 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
> 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.
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/Uranus_rings_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/2003/05/22/earth_americas250.jpg
Szczepan Bialek
Dec 28, 2012, 12:38:49 PM12/28/12
to
"Pete L" <peterla...@hotmail.com> napisal w wiadomosci
news:f6180bc3-1790-485a...@z2g2000vbx.googlegroups.com...
>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.
> 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
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.
>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?
More comets, more solar wind and in the result the higher temperature on the
Earth.
Now the interplanetary dust is behind the Mars.
S*
newshound
Dec 28, 2012, 4:55:18 PM12/28/12
to
--
For every complex problem, there is a solution which is simple, neat,
and wrong.
H L Menken
0 new messages