Shindell, D.T., Schmidt, G.A., Miller, R.L., Mann, M.E., Volcanic and Solar Forcing of Climate
Change during the Preindustrial Era, Journal of Climate, in press, 2003.
ftp://holocene.evsc.virginia.edu/pub...3-preprint.pdf
at
http://holocene.evsc.virginia.edu/Ma.../articles.html
I think these results may be about to be presented at the annual AGU meeting,

--
regards,
david
(add 17 to waghorne to reply)

"Waghorn" wrote in message
...
Shindell, D.T., Schmidt, G.A., Miller, R.L., Mann, M.E., Volcanic and Solar
Forcing of Climate
Change during the Preindustrial Era, Journal of Climate, in press, 2003.
ftp://holocene.evsc.virginia.edu/pub...3-preprint.pdf
at
http://holocene.evsc.virginia.edu/Ma.../articles.html
I think these results may be about to be presented at the annual AGU
meeting,

Although copying a paper into a news group may be considered a breach of
copyright, AFAIK, it is acceptable and usual to copy the abstract. So here it
is;
--------
The climate response to variability in volcanic aerosols and solar irradiance,
the primary forcings during the preindustrial era, is examined in a
stratosphere-resolving general circulation model. The best agreement with
historical and proxy data is obtained using both forcings, each of which has a
significant effect on global mean temperatures. However, their regional
climate impacts in the Northern Hemisphere are quite different. While
the short-term continental winter warming response to volcanism is well known,
it is shown that due to opposing dynamical and radiative effects, the
long-term
(decadal mean) regional response is not significant compared to unforced
variability for either the winter or the annual average. In contrast, the
long-term
regional response to solar forcing greatly exceeds unforced variability for
both
time averages, as the dynamical and radiative effects reinforce one another,
and produces climate anomalies similar to those seen during the Little Ice
Age.
Thus, long-term regional changes during the preindustrial appear to have been
dominated by solar forcing.
-------
I am not sure if David was trying to suggest that climate change can be caused
by factors other than greenhouse gasses, something that no serious
climatologist would dispute. However, he seems to have added to the evidence
that the Little Ice Age was caused by solar forcing, something he claimed was
in dispute, if I recall correctly.

Cheers, Alastair.




--
regards,
david
(add 17 to waghorne to reply)

I am not sure if David was trying to suggest that climate change can be caused
by factors other than greenhouse gasses, something that no serious
climatologist would dispute.

Not at all,I merely posted the link to the paper ,nb without comment on the content. I thought it
wld be of interest to others here,re recent discussions.
However, he seems to have added to the evidence
that the Little Ice Age was caused by solar forcing, something he claimed was
in dispute, if I recall correctly.

Cheers, Alastair.

IIRC I've not argued as such (I presume you mean me).It's generally accepted there was some kind of
solar influence at work in the LIA,but the nature and timescale of the influence is open to question
as are the global extent and magnitude of the LIA,and it's effects.What's interesting about the
paper I think is the possible constraints on the magnitude of solar irradiance and volcanic forcings
and internal variability in the period in question,lending necessary perspective to recent climate
change,

--
regards,
david
(add 17 to waghorne to reply)

I am still not sure what you mean when you write "lending necessary
perspective
to recent climate change". Presumably you mean since volcanic and solar
influences can cause a 1C change then it puts the 0.6C of the last century
into
perspective. However, it should also put into perspective the 6C now expected
this century.

Cheers, Alastair.
Oh dear ,are we all going to be examined for our 'sceptical'and 'heretical' views ?
....bring on the comfy chair...


"eppur si muove"

David.

In article ,
Alastair McDonald k
writes:
However, it should also put into perspective the 6C now expected
this century.

Surely as large a warming as that is not the consensus view, even
amongst scientists who are convinced of the reality of anthrogenic
global warming?
--
John Hall

"Distrust any enterprise that requires new clothes."
Henry David Thoreau (1817-1862)

"John Hall" wrote in message
...
In article ,
Alastair McDonald k
writes:
However, it should also put into perspective the 6C now expected
this century.

Surely as large a warming as that is not the consensus view, even
amongst scientists who are convinced of the reality of anthrogenic
global warming?
--
John Hall

"Distrust any enterprise that requires new clothes."
Henry David Thoreau (1817-1862)

The problem is there is not a consensus view of warming over the next
century.

Firstly no one knows how much CO2 will be in the atmosphere
in 2099. We might come to our senses, we might not.

Secondly there are a range of estimates for the effects from 1.4C
to 5.8C. Since these estimates have not included the positive
feedback from biological sources, such as methane from warming
peat bogs, I prefer to take the upper limit rounded up to 6.0C. In
cases where only perspective is being considered this seems fair
enough to me. You should not assume that the consensus view
is the mean of 1.5 and 5.8. That is like saying the average family
contins 2.1 children. No family contains 2.1 children and no computer
model is predicting a 3.55C rise in temperture in 2099. Lets face it
we don't know what the increase in CET will be in January 2004, that
is if it does rise.

Cheers, Alastair.

In article ,
Alastair McDonald k
writes:

"John Hall" wrote in message
...
In article ,
Alastair McDonald k
writes:
However, it should also put into perspective the 6C now expected
this century.

Surely as large a warming as that is not the consensus view, even
amongst scientists who are convinced of the reality of anthrogenic
global warming?

The problem is there is not a consensus view of warming over the next
century.

Firstly no one knows how much CO2 will be in the atmosphere
in 2099. We might come to our senses, we might not.

Secondly there are a range of estimates for the effects from 1.4C
to 5.8C.
Since these estimates have not included the positive
feedback from biological sources, such as methane from warming
peat bogs, I prefer to take the upper limit rounded up to 6.0C.
snip

It would have been better had you made it clear originally that this was
just your own view. Simply to say "the 6C now expected this century"
seems rather misleading. Yes, _you_ expect that, but it was phrased in
such a way as to sound like the received wisdom of the climatological
community. You may turn out to be right with your 6C figure, but you are
surely less of an expert than the scientists working full-time on this
problem. (And surely some of the estimates _must_ have included
allowance for the positive feedback from biological sources?)

I hope that you aren't so convinced that countering GW is essential that
you are prepared to exaggerate the likely effects in order to encourage
people to act.
--
John Hall

"Distrust any enterprise that requires new clothes."
Henry David Thoreau (1817-1862)

"John Hall" wrote in message
...
In article ,

Secondly there are a range of estimates for the effects from 1.4C
to 5.8C.
Since these estimates have not included the positive
feedback from biological sources, such as methane from warming
peat bogs, I prefer to take the upper limit rounded up to 6.0C.
snip

It would have been better had you made it clear originally that this was
just your own view. Simply to say "the 6C now expected this century"
seems rather misleading. Yes, _you_ expect that, but it was phrased in
such a way as to sound like the received wisdom of the climatological
community. You may turn out to be right with your 6C figure, but you are
surely less of an expert than the scientists working full-time on this
problem. (And surely some of the estimates _must_ have included
allowance for the positive feedback from biological sources?)

I hope that you aren't so convinced that countering GW is essential that
you are prepared to exaggerate the likely effects in order to encourage
people to act.

I, at least, quoted figures to back up my assertion unlike David who only
hinted at some implication. To deal with this matter properly would require
a fairly long paper, and the longer the paper the less likely that it would be
error free. So I will keep my remarks short.

The Hadley Centre have just released their latest brochure entitled;
Climate change observations and predictions:
Recent research on climate change science from the Hadley Centre, December
2003
http://www.metoffice.com/research/ha...003/global.pdf

In it they use a temperature rise of 3C to illustrate future climate. See last
line page 9. But this is for temperature rise this century so we can add
0.6C, for the last century to give the total rise of 3.6C . Moreover, since
they are averaging between 2.0C and a max of 4.5C! it is obvious (to me
at least) they have not included the addional 1.5C found by Hadley's Cox
et al. in their paper in Nature 408, 184 - 187 (2000); "Acceleration of global
warming due to carbon-cycle feedbacks in a coupled climate model"

The abstract reads;

-----------------------

The continued increase in the atmospheric concentration of carbon dioxide due
to anthropogenic emissions is predicted to lead to significant changes in
climate. About half of the current emissions are being absorbed by the ocean
and by land ecosystems, but this absorption is sensitive to climate as well as
to atmospheric carbon dioxide concentrations, creating a feedback loop.
General circulation models have generally excluded the feedback between
climate and the biosphere, using static vegetation distributions and CO2
concentrations from simple carbon-cycle models that do not include climate
change. Here we present results from a fully coupled, three-dimensional
carbon-climate model, indicating that carbon-cycle feedbacks could
significantly accelerate climate change over the twenty-first century. We find
that under a 'business as usual' scenario, the terrestrial biosphere acts as
an overall carbon sink until about 2050, but turns into a source thereafter.
By 2100, the ocean uptake rate of 5 Gt C yr-1 is balanced by the terrestrial
carbon source, and atmospheric CO2 concentrations are 250 p.p.m.v. higher in
our fully coupled simulation than in uncoupled carbon models, resulting in a
global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle
feedback.

-----------------------

Adding their 1.5C to the 3.6C already calculated comes to 5.1C. I don't
really think that using 6C is a gross exageration. Moreover the figure used
by Hadley, 3C, seems to me to have be the one which is misleading and
has been chosen in order not to appear alarmist.

I do not expect you to agree, but I do feel that these figures from the Hadley
Centre are not clear. There is confusion about whether the temperature rise
is over this centrury or over the period since the start of the Industrial
Revolution. There is confusion over whether the rise is due to a doubling
of CO2 in the atmosphere or has occurred over a fixed period. If it is a
fixed period then there is confusion over which scenario is being used. And
finally there is confusion over whether biological feedbacks are being
included.

Perhaps the IPCC might like to consider that at their next meeting.

Cheers, Alastair.

Alistair Mcdonald wrote-
I, at least, quoted figures to back up my assertion unlike David who only
hinted at some implication.
Waghorn wrote-
What's interesting about the
paper I think is the possible constraints on the magnitude of solar irradiance and volcanic forcings
and internal variability in the period in question,lending necessary perspective to recent climate
change,

Cf.
"Understanding the
magnitude and causes of the forced climate variations, and distinguishing them
from unforced, internal variability, is important for historical purposes, and is a
crucial test for climate models attempting to predict future climate variations."
Volcanic and Solar Forcing of Climate Change during the Preindustrial Era
Shindell et al,2003,p3.

correspondence closed,

--
regards,
david
(add 17 to waghorne to reply)

"Waghorn" wrote in message
...

Alistair Mcdonald wrote-
I, at least, quoted figures to back up my assertion unlike David who only
hinted at some implication.
Waghorn wrote-
What's interesting about the
paper I think is the possible constraints on the magnitude of solar
irradiance and volcanic forcings
and internal variability in the period in question,lending necessary
perspective to recent climate
change,

Cf.
"Understanding the
magnitude and causes of the forced climate variations, and distinguishing
them
from unforced, internal variability, is important for historical purposes,
and is a
crucial test for climate models attempting to predict future climate
variations."
Volcanic and Solar Forcing of Climate Change during the Preindustrial Era
Shindell et al,2003,p3.

correspondence closed,

All I was saying is that I find it difficult to judge the perspective without
putting figures on both the changes which took place in the period in
question and those which are currently taking place. I supplied some
for those currently taking place. Half a loaf is better than no bread!

You seem to be saying the Shindell et al. are implying that "the
magnitude and causes" of the LIA can be used "to predict future
climate variations." As I understand it, they are saying a reconstruction
of the LIA can be used to test climate models before they are used
to predict future warming.

Cheers, Alastair.